PCA9685BS ,16-channel, 12-bit PWM Fm+ I2C-bus LED controllerFeatures and benefits 16 LED drivers. Each output programmable at: Off On Programmable LED brig ..
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PCA9685BS-PCA9685PW
16-channel, 12-bit PWM Fm+ I2C-bus LED controller
1. General descriptionThe PCA9685 is an I2 C-bus controlled 16-channel LED controller optimized for LCD
Red/Green/Blue/Amber (RGBA) color backlighting applications. Each LED output has its
own 12-bit resolution (4096 steps) fixed frequency individual PWM controller that operates
at a programmable frequency from a typical of 40 Hz to 1000 Hz with a duty cycle that is
adjustable from 0 % to 100 % to allow the LED to be set to a specific brightness value.
All outputs are set to the same PWM frequency.
Each LED output can be off or on (no PWM control), or set at its individual PWM controller
value. The LED output driver is programmed to be either open-drain with a 25 mA current
sink capability at 5 V or totem pole with a 25 mA sink, 10 mA source capability at 5 V. The
PCA9685 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs and
outputs are 5.5 V tolerant. LEDs can be directly connected to the LED output (up to mA, 5.5 V) or controlled with external drivers and a minimum amount of discrete
components for larger current or higher voltage LEDs.
The PCA9685 is in the new Fast-mode Plus (Fm+) family. Fm+ devices offer higher
frequency (up to 1 MHz) and more densely populated bus operation (up to 4000 pF).
Although the PCA9635 and PCA9685 have many similar features, the PCA9685 has
some unique features that make it more suitable for applications such as LCD
backlighting and Ambilight:
The PCA9685 allows staggered LED output on and off times to minimize current
surges. The on and off time delay is independently programmable for each of the channels. This feature is not available in PCA9635.
The PCA9685 has 4096 steps (12-bit PWM) of individual LED brightness control. The
PCA9635 has only 256 steps (8-bit PWM).
When multiple LED controllers are incorporated in a system, the PWM pulse widths
between multiple devices may differ if PCA9635s are used. The PCA9685 has a
programmable prescaler to adjust the PWM pulse widths of multiple devices.
The PCA9685 has an external clock input pin that will accept user-supplied clock
(50 MHz max.) in place of the internal 25 MHz oscillator. This feature allows
synchronization of multiple devices. The PCA9635 does not have external clock input
feature.
Like the PCA9635, PCA9685 also has a built-in oscillator for the PWM control.
However, the frequency used for PWM control in the PCA9685 is adjustable from
about 40 Hz to 1000 Hz as compared to the typical 97.6 kHz frequency of the
PCA9635. This allows the use of PCA9685 with external power supply controllers. All
bits are set at the same frequency.
The Power-On Reset (POR) default state of LEDn output pins is LOW in the case of
PCA9685. It is HIGH for PCA9635.
PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
Rev. 3 — 2 September 2010 Product data sheet
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controllerThe active LOW Output Enable input pin (OE) allows asynchronous control of the LED
outputs and can be used to set all the outputs to a defined I2 C-bus programmable logic
state. The OE can also be used to externally ‘pulse width modulate’ the outputs, which is
useful when multiple devices need to be dimmed or blinked together using software
control.
Software programmable LED All Call and three Sub Call I2 C-bus addresses allow all or
defined groups of PCA9685 devices to respond to a common I2 C-bus address, allowing
for example, all red LEDs to be turned on or off at the same time or marquee chasing
effect, thus minimizing I2 C-bus commands. Six hardware address pins allow up to devices on the same bus.
The Software Reset (SWRST) General Call allows the master to perform a reset of the
PCA9685 through the I2 C-bus, identical to the Power-On Reset (POR) that initializes the
registers to their default state causing the outputs to be set LOW. This allows an easy and
quick way to reconfigure all device registers to the same condition via software.
2. Features and benefits 16 LED drivers. Each output programmable at: Off On Programmable LED brightness Programmable LED turn-on time to help reduce EMI1 MHz Fast-mode Plus compatible I2 C-bus interface with 30 mA high drive capability
on SDA output for driving high capacitive buses 4096-step (12-bit) linear programmable brightness per LED output varying from fully
off (default) to maximum brightness LED output frequency (all LEDs) typically varies from 40 Hz to 1000 Hz (Default of 1Eh
in PRE_SCALE register results in a 200 Hz refresh rate with oscillator clock of MHz.) Sixteen totem pole outputs (sink 25 mA and source 10 mA at 5 V) with software
programmable open-drain LED outputs selection (default at totem pole). No input
function. Output state change programmable on the Acknowledge or the STOP Command to
update outputs byte-by-byte or all at the same time (default to ‘Change on STOP’). Active LOW Output Enable (OE) input pin. LEDn outputs programmable to logic1,
logic 0 (default at power-up) or ‘high-impedance’ when OE is HIGH. 6 hardware address pins allow 62 PCA9685 devices to be connected to the same 2 C-bus Toggling OE allows for hardware LED blinking 4 software programmable I2 C-bus addresses (one LED All Call address and three LED
Sub Call addresses) allow groups of devices to be addressed at the same time in any
combination (for example, one register used for ‘All Call’ so that all the PCA9685s on
the I2 C-bus can be addressed at the same time and the second register used for three
different addresses so that 1 ⁄3 of all devices on the bus can be addressed at the same
time in a group). Software enable and disable for these I2 C-bus address. Software Reset feature (SWRST General Call) allows the device to be reset through
the I2 C-bus
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller 25 MHz typical internal oscillator requires no external components External 50 MHz (max.) clock input Internal power-on reset Noise filter on SDA/SCL inputs Edge rate control on outputs No output glitches on power-up Supports hot insertion Low standby current Operating power supply voltage range of 2.3 V to 5.5V 5.5 V tolerant inputs −40 °C to +85 °C operation ESD protection exceeds 2000 V HBM per JESD22-A114, 200 V MM per
JESD22-A115 and 1000 V CDM per JESD22-C101 Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA Packages offered: TSSOP28, HVQFN28
3. Applications RGB or RGBA LED drivers LED status information LED displays LCD backlights Keypad backlights for cellular phones or handheld devices
4. Ordering information[1] PCA9685PW/Q900 is AEC-Q100 compliant. Contact i2c.support for PPAP.
Table 1. Ordering informationPCA9685PW PCA9685PW TSSOP28 plastic thin shrink small outline package; leads; body width 4.4 mm
SOT361-1
PCA9685PW/Q900[1] PCA9685PW TSSOP28 plastic thin shrink small outline package; leads; body width 4.4 mm
SOT361-1
PCA9685BS P9685 HVQFN28 plastic thermal enhanced very thin quad flat
package; no leads; 28 terminals;
body6×6× 0.85 mm
SOT788-1
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
5. Block diagramNXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
6. Pinning information
6.1 Pinning
6.2 Pin description
Table 2. Pin description 1 26 I address input 0 2 27 I address input 1 3 28 I address input 2 4 1 I address input 3 5 2 I address input 4
LED0 6 3 O LED driver 0
LED1 7 4 O LED driver 1
LED2 8 5 O LED driver 2
LED3 9 6 O LED driver 3
LED4 10 7 O LED driver 4
LED5 11 8 O LED driver 5
LED6 12 9 O LED driver 6
LED7 13 10 O LED driver 7
VSS 14 11[1] power supply supply ground
LED8 15 12 O LED driver 8
LED9 16 13 O LED driver 9
LED10 17 14 O LED driver 10
LED11 18 15 O LED driver 11
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller[1] HVQFN28 package die supply ground is connected to both VSS pin and exposed center pad. VSS pin must
be connected to supply ground for proper device operation. For enhanced thermal, electrical, and board
level performance, the exposed pad needs to be soldered to the board using a corresponding thermal pad
on the board and for proper heat conduction through the board, thermal vias need to be incorporated in the
PCB in the thermal pad region.
[2] This pin must be grounded when this feature is not used.
7. Functional descriptionRefer to Figure 1 “Block diagram of PCA9685”.
7.1 Device addressesFollowing a START condition, the bus master must output the address of the slave it is
accessing.
There are a maximum of 64 possible programmable addresses using the 6 hardware
address pins. Two of these addresses, Software Reset and LED All Call, cannot be used
because their default power-up state is ON, leaving a maximum of 62 addresses. Using
other reserved addresses, as well as any other subcall address, will reduce the total
number of possible addresses even further.
7.1.1 Regular I2 C-bus slave addressThe I2 C-bus slave address of the PCA9685 is shown in Figure 4. To conserve power, no
internal pull-up resistors are incorporated on the hardware selectable address pins and
they must be pulled HIGH or LOW.
Remark: Using reserved I2 C-bus addresses will interfere with other devices, but only if
the devices are on the bus and/or the bus will be open to other I2 C-bus systems at some
later date. In a closed system where the designer controls the address assignment these
addresses can be used since the PCA9685 treats them like any other address. The
LEDAll Call, Software Reset and PCA9564 or PCA9665 slave address (if on the bus) can
never be used for individual device addresses.
PCA9685 LEDAll Call address (1110 000) and Software Reset (0000 0110) which are
active on start-up
LED12 19 16 O LED driver 12
LED13 20 17 O LED driver 13
LED14 21 18 O LED driver 14
LED15 22 19 O LED driver 15 23 20 I active LOW output enable 24 21 I address input 5
EXTCLK 25 22 I external clock input[2]
SCL 26 23 I serial clock line
SDA 27 24 I/O serial data line
VDD 28 25 power supply supply voltage
Table 2. Pin description …continued
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller PCA9564 (0000 000) or PCA9665 (1110 000) slave address which is active on
start-up
‘reserved for future use’ I2 C-bus addresses (0000 011, 1111 1XX)
slave devices that use the 10-bit addressing scheme (1111 0XX)
slave devices that are designed to respond to the General Call address (0000 000)
which is used as the software reset address
High-speed mode (Hs-mode) master code (0000 1XX)
The last bit of the address byte defines the operation to be performed. When set to logic1
a read is selected, while a logic 0 selects a write operation.
7.1.2 LED All Call I2 C-bus address Default power-up value (ALLCALLADR register): E0h or 1110 000X
Programmable through I2 C-bus (volatile programming)
At power-up, LED All Call I2 C-bus address is enabled. PCA9685 sends an ACK when
E0h (R/W= 0) or E1h (R/W= 1) is sent by the master.
See Section 7.3.7 “ALLCALLADR, LED All Call I2 C-bus address” for more detail.
Remark: The default LED All Call I2 C-bus address (E0h or 1110 000X) must not be used
as a regular I2 C-bus slave address since this address is enabled at power-up. All the
PCA9685s on the I2 C-bus will acknowledge the address if sent by the I2 C-bus master.
7.1.3 LED Sub Call I2 C-bus addresses 3 different I2 C-bus addresses can be used
Default power-up values:
SUBADR1 register: E2h or 1110 001X
SUBADR2 register: E4h or 1110 010X
SUBADR3 register: E8h or 1110 100X
Programmable through I2 C-bus (volatile programming)
At power-up, Sub Call I2 C-bus addresses are disabled. PCA9685 does not send an
ACK when E2h (R/W =0) or E3h (R/W= 1), E4h (R/W= 0) or E5h (R/W =1), or
E8h (R/W= 0) or E9h (R/W= 1) is sent by the master.
See Section 7.3.6 “SUBADR1 to SUBADR3, I2 C-bus subaddress 1 to 3” for more detail.
Remark: The default LED Sub Call I2 C-bus addresses may be used as regular I2 C-bus
slave addresses as long as they are disabled.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.1.4 Software Reset I2 C-bus addressThe address shown in Figure 5 is used when a reset of the PCA9685 needs to be
performed by the master. The Software Reset address (SWRST Call) must be used with
R/W= logic 0. If R/W= logic 1, the PCA9685 does not acknowledge the SWRST. See
Section 7.6 “Software reset” for more detail.
Remark: The Software Reset I2 C-bus address is a reserved address and cannot be used
as a regular I2 C-bus slave address or as an LED All Call or LED Sub Call address.
7.2 Control registerFollowing the successful acknowledgement of the slave address, LED All Call address or
LED Sub Call address, the bus master will send a byte to the PCA9685, which will be
stored in the Control register.
This register is used as a pointer to determine which register will be accessed.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.3 Register definitionsTable 3. Register summary 00 0 0 000 000 MODE1 read/write Mode register 1 01 0 0 000 001 MODE2 read/write Mode register 2 02 0 0 0 0 0 0 1 0 SUBADR1 read/writeI2 C-bus subaddress 1 03 0 0 0 0 0 0 1 1 SUBADR2 read/writeI2 C-bus subaddress 2 04 0 0 0 0 0 1 0 0 SUBADR3 read/writeI2 C-bus subaddress 3 05 0 0 0 0 0 1 0 1 ALLCALLADR read/write LED All Call I2 C-bus
address 06 0 0 0 0 0 1 1 0 LED0_ON_L read/write LED0 output and
brightness control byte 0 07 0 0 0 0 0 1 1 1 LED0_ON_H read/write LED0 output and
brightness control byte 1 08 0 0 0 0 1 0 0 0 LED0_OFF_L read/write LED0 output and
brightness control byte 2 09 0 0 0 0 1 0 0 1 LED0_OFF_H read/write LED0 output and
brightness control byte 3 0A 0 0 0 0 1 0 1 0 LED1_ON_L read/write LED1 output and
brightness control byte 0 0B 0 0 0 0 1 0 1 1 LED1_ON_H read/write LED1 output and
brightness control byte 1 0C 0 0 0 0 1 1 0 0 LED1_OFF_L read/write LED1 output and
brightness control byte 2 0D 0 0 0 0 1 1 0 1 LED1_OFF_H read/write LED1 output and
brightness control byte 3 0E 0 0 0 0 1 1 1 0 LED2_ON_L read/write LED2 output and
brightness control byte 0 0F 0 0 0 0 1 1 1 1 LED2_ON_H read/write LED2 output and
brightness control byte 1 10 0 0 0 1 0 0 0 0 LED2_OFF_L read/write LED2 output and
brightness control byte 2 11 0 0 0 1 0 0 0 1 LED2_OFF_H read/write LED2 output and
brightness control byte 3 12 0 0 0 1 0 0 1 0 LED3_ON_L read/write LED3 output and
brightness control byte 0 13 0 0 0 1 0 0 1 1 LED3_ON_H read/write LED3 output and
brightness control byte 1 14 0 0 0 1 0 1 0 0 LED3_OFF_L read/write LED3 output and
brightness control byte 2 15 0 0 0 1 0 1 0 1 LED3_OFF_H read/write LED3 output and
brightness control byte 3
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller 16 0 0 0 1 0 1 1 0 LED4_ON_L read/write LED4 output and
brightness control byte 0 17 0 0 0 1 0 1 1 1 LED4_ON_H read/write LED4 output and
brightness control byte 1 18 0 0 0 1 1 0 0 0 LED4_OFF_L read/write LED4 output and
brightness control byte 2 19 0 0 0 1 1 0 0 1 LED4_OFF_H read/write LED4 output and
brightness control byte 3 1A 0 0 0 1 1 0 1 0 LED5_ON_L read/write LED5 output and
brightness control byte 0 1B 0 0 0 1 1 0 1 1 LED5_ON_H read/write LED5 output and
brightness control byte 1 1C 0 0 0 1 1 1 0 0 LED5_OFF_L read/write LED5 output and
brightness control byte 2 1D 0 0 0 1 1 1 0 1 LED5_OFF_H read/write LED5 output and
brightness control byte 3 1E 0 0 0 1 1 1 1 0 LED6_ON_L read/write LED6 output and
brightness control byte 0 1F 0 0 0 1 1 1 1 1 LED6_ON_H read/write LED6 output and
brightness control byte 1 20 0 0 1 0 0 0 0 0 LED6_OFF_L read/write LED6 output and
brightness control byte 2 21 0 0 1 0 0 0 0 1 LED6_OFF_H read/write LED6 output and
brightness control byte 3 22 0 0 1 0 0 0 1 0 LED7_ON_L read/write LED7 output and
brightness control byte 0 23 0 0 1 0 0 0 1 1 LED7_ON_H read/write LED7 output and
brightness control byte 1 24 0 0 1 0 0 1 0 0 LED7_OFF_L read/write LED7 output and
brightness control byte 2 25 0 0 1 0 0 1 0 1 LED7_OFF_H read/write LED7 output and
brightness control byte 3 26 0 0 1 0 0 1 1 0 LED8_ON_L read/write LED8 output and
brightness control byte 0 27 0 0 1 0 0 1 1 1 LED8_ON_H read/write LED8 output and
brightness control byte 1 28 0 0 1 0 1 0 0 0 LED8_OFF_L read/write LED8 output and
brightness control byte 2 29 0 0 1 0 1 0 0 1 LED8_OFF_H read/write LED8 output and
brightness control byte 3
Table 3. Register summary …continued
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller 2A 0 0 1 0 1 0 1 0 LED9_ON_L read/write LED9 output and
brightness control byte 0 2B 0 0 1 0 1 0 1 1 LED9_ON_H read/write LED9 output and
brightness control byte 1 2C 0 0 1 0 1 1 0 0 LED9_OFF_L read/write LED9 output and
brightness control byte 2 2D 0 0 1 0 1 1 0 1 LED9_OFF_H read/write LED9 output and
brightness control byte 3 2E 0 0 1 0 1 1 1 0 LED10_ON_L read/write LED10 output and
brightness control byte 0 2F 0 0 1 0 1 1 1 1 LED10_ON_H read/write LED10 output and
brightness control byte 1 30 0 0 1 1 0 0 0 0 LED10_OFF_L read/write LED10 output and
brightness control byte 2 31 0 0 1 1 0 0 0 1 LED10_OFF_H read/write LED10 output and
brightness control byte 3 32 0 0 1 1 0 0 1 0 LED11_ON_L read/write LED11 output and
brightness control byte 0 33 0 0 1 1 0 0 1 1 LED11_ON_H read/write LED11 output and
brightness control byte 1 34 0 0 1 1 0 1 0 0 LED11_OFF_L read/write LED11 output and
brightness control byte 2 35 0 0 1 1 0 1 0 1 LED11_OFF_H read/write LED11 output and
brightness control byte 3 36 0 0 1 1 0 1 1 0 LED12_ON_L read/write LED12 output and
brightness control byte 0 37 0 0 1 1 0 1 1 1 LED12_ON_H read/write LED12 output and
brightness control byte 1 38 0 0 1 1 1 0 0 0 LED12_OFF_L read/write LED12 output and
brightness control byte 2 39 0 0 1 1 1 0 0 1 LED12_OFF_H read/write LED12 output and
brightness control byte 3 3A 0 0 1 1 1 0 1 0 LED13_ON_L read/write LED13 output and
brightness control byte 0 3B 0 0 1 1 1 0 1 1 LED13_ON_H read/write LED13 output and
brightness control byte 1 3C 0 0 1 1 1 1 0 0 LED13_OFF_L read/write LED13 output and
brightness control byte 2 3D 0 0 1 1 1 1 0 1 LED13_OFF_H read/write LED13 output and
brightness control byte 3
Table 3. Register summary …continued
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller[1] Writes to PRE_SCALE register are blocked when SLEEP bit is logic 0 (MODE1).
[2] Reserved. Writes to this register may cause unpredictable results.
Remark: Auto Increment past register 69 will point to MODE1 register (register 0). Auto Increment also works from register 250 to register 254, then rolls over to register 0. 3E 0 0 1 1 1 1 1 0 LED14_ON_L read/write LED14 output and
brightness control byte 0 3F 0 0 1 1 1 1 1 1 LED14_ON_H read/write LED14 output and
brightness control byte 1 40 0 1 0 0 0 0 0 0 LED14_OFF_L read/write LED14 output and
brightness control byte 2 41 0 1 0 0 0 0 0 1 LED14_OFF_H read/write LED14 output and
brightness control byte 3 42 0 1 0 0 0 0 1 0 LED15_ON_L read/write LED15 output and
brightness control byte 0 43 0 1 0 0 0 0 1 1 LED15_ON_H read/write LED15 output and
brightness control byte 1 44 0 1 0 0 0 1 0 0 LED15_OFF_L read/write LED15 output and
brightness control byte 2 45 0 1 0 0 0 1 0 1 LED15_OFF_H read/write LED15 output and
brightness control byte 3
... reserved for future use
250 FA 1 1 1 1 1 0 1 0 ALL_LED_ON_L write/read
zero
load all the LEDn_ON
registers, byte0
251 FB 1 1 1 1 1 0 1 1 ALL_LED_ON_H write/read
zero
load all the LEDn_ON
registers, byte1
252 FC 1 1 1 1 1 1 0 0 ALL_LED_OFF_L write/read
zero
load all the LEDn_OFF
registers, byte0
253 FD 1 1 1 1 1 1 0 1 ALL_LED_OFF_H write/read
zero
load all the LEDn_OFF
registers, byte1
254 FE 1 1 1 1 1 1 1 0 PRE_SCALE[1] read/write prescaler for output
frequency
255 FF 1 1 111 111 TestMode[2] read/write defines the test mode to
be entered
... All further addresses are reserved for future use; reserved addresses will not be acknowledged.
Table 3. Register summary …continued
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.3.1 Mode register 1, MODE1[1] When the Auto Increment flag is set, AI= 1, the Control register is automatically incremented after a read or write. This allows the user
to program the registers sequentially.
[2] It takes 500 μs max. for the oscillator to be up and running once SLEEP bit has been set to logic 0. Timings on LEDn outputs are not
guaranteed if PWM control registers are accessed within the 500 μs window. There is no start-up delay required when using the
EXTCLK pin as the PWM clock.
[3] No PWM control is possible when the oscillator is off.
[4] When the oscillator is off (Sleep mode) the LEDn outputs cannot be turned on, off or dimmed/blinked.
Table 4. MODE1 - Mode register 1 (address 00h) bit descriptionLegend: * default value. RESTART R Shows state of RESTART logic. See Section 7.3.1.1 for detail. User writes logic 1 to this bit to clear it to logic 0. A user write of logic 0 will have no
effect. See Section 7.3.1.1 for detail. Restart disabled. Restart enabled. EXTCLK R/W To use the EXTCLK pin, this bit must be set by the following sequence: Set the SLEEP bit in MODE1. This turns off the internal oscillator. Write logic 1s to both the SLEEP and EXTCLK bits in MODE1. The switch is
now made. The external clock can be active during the switch because the
SLEEP bit is set.
This bit is a ‘sticky bit’, that is, it cannot be cleared by writing a logic 0 to it. The
EXTCLK bit can only be cleared by a power cycle or software reset.
EXTCLK range is DC to 50 MHz. Use internal clock. Use EXTCLK pin clock. AI R/W 0* Register Auto-Increment disabled[1] Register Auto-Increment enabled. SLEEP R/W 0 Normal mode[2] Low power mode. Oscillator off [3][4] SUB1 R/W 0* PCA9685 does not respond to I2 C-bus subaddress 1. PCA9685 responds to I2 C-bus subaddress 1. SUB2 R/W 0* PCA9685 does not respond to I2 C-bus subaddress 2. PCA9685 responds to I2 C-bus subaddress 2. SUB3 R/W 0* PCA9685 does not respond to I2 C-bus subaddress 3. PCA9685 responds to I2 C-bus subaddress 3. ALLCALL R/W 0 PCA9685 does not respond to LED All Call I2 C-bus address. PCA9685 responds to LED All Call I2 C-bus address.
refresh_rate EXTCLK
4096 prescale1+()×------------------ ----------------- --------------------=
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.3.1.1 Restart modeIf the PCA9685 is operating and the user decides to put the chip to sleep (setting MODE1
bit 4) without stopping any of the PWM channels, the RESTART bit (MODE1 bit 7) will be
set to logic 1 at the end of the PWM refresh cycle. The contents of each PWM register are
held valid when the clock is off.
To restart all of the previously active PWM channels with a few I2 C-bus cycles do the
following steps: Read MODE1 register. Check that bit 7 (RESTART) is a logic 1. If it is, clear bit 4 (SLEEP). Allow time for
oscillator to stabilize (500 μs). Write logic 1 to bit 7 of MODE1 register. All PWM channels will restart and the
RESTART bit will clear.
Remark: The SLEEP bit must be logic 0 for at least 500 μs, before a logic 1 is written into
the RESTART bit.
Other actions that will clear the RESTART bit are: Power cycle.I2 C Software Reset command. If the MODE2 OCH bit is logic 0, write to any PWM register then issue an I2 C-bus
STOP. If the MODE2 OCH bit is logic 1, write to all four PWM registers in any PWM channel.
Likewise, if the user does an orderly shutdown1 of all the PWM channels before setting
the SLEEP bit, the RESTART bit will be cleared. If this is done the contents of all PWM
registers are invalidated and must be reloaded before reuse.
An example of the use of the RESTART bit would be the restoring of a customer’s laptop
LCD backlight intensity coming out of Standby to the level it was before going into
Standby. Two methods can be used to do an orderly shutdown. The fastest is to write a logic 1 to bit 4 in register ALL_LED_OFF_H. The
other method is to write logic 1 to bit 4 in each active PWM channel LEDn_OFF_H register.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.3.2 Mode register 2, MODE2[1] See Section 7.7 “Using the PCA9685 with and without external drivers” for more details. Normal LEDs can be driven directly in either
mode. Some newer LEDs include integrated Zener diodes to limit voltage transients, reduce EMI, protect the LEDs and these must be
driven only in the open-drain mode to prevent overheating the IC.
[2] Change of the outputs at the STOP command allows synchronizing outputs of more than one PCA9685. Applicable to registers from
06h (LED0_ON_L) to 45h (LED15_OFF_H) only. 1 or more registers can be written, in any order, before STOP.
[3] Update on ACK requires all 4 PWM channel registers to be loaded before outputs will change on the last ACK.
[4] See Section 7.4 “Active LOW output enable input” for more details.
7.3.3 LED output and PWM controlThe turn-on time of each LED driver output and the duty cycle of PWM can be controlled
independently using the LEDn_ON and LEDn_OFF registers.
There will be two 12-bit registers per LED output. These registers will be programmed by
the user. Both registers will hold a value from 0 to 4095. One 12-bit register will hold a
value for the ON time and the other 12-bit register will hold the value for the OFF time. The
ON and OFF times are compared with the value of a 12-bit counter that will be running
continuously from 0000h to 0FFFh (0 to 4095 decimal).
Update on ACK requires all 4 PWM channel registers to be loaded before outputs will
change on the last ACK.
The ON time, which is programmable, will be the time the LED output will be asserted and
the OFF time, which is also programmable, will be the time when the LED output will be
negated. In this way, the phase shift becomes completely programmable. The resolution
for the phase shift is 1 ⁄4096 of the target frequency. Table 6 lists these registers.
The following two examples illustrate how to calculate values to be loaded into these
registers.
Table 5. MODE2 - Mode register 2 (address 01h) bit descriptionLegend: * default value.
7 to 5 - read only 000* reserved
4INVRT[1] R/W 0* Output logic state not inverted. Value to use when external driver used.
Applicable when OE =0. Output logic state inverted. Value to use when no external driver used.
Applicable when OE =0. OCH R/W 0* Outputs change on STOP command[2]. Outputs change on ACK[3].
2OUTDRV[1] R/W 0 The 16 LEDn outputs are configured with an open-drain structure. The 16 LEDn outputs are configured with a totem pole structure.
1to0 OUTNE[1:0][4] R/W 00* When OE = 1 (output drivers not enabled), LEDn = 0. When OE = 1 (output drivers not enabled):
LEDn = 1 when OUTDRV=1
LEDn= high-impedance when OUTDRV= 0 (same as OUTNE[1:0]= 10) When OE = 1 (output drivers not enabled), LEDn = high-impedance.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
Example 1: (assumes that the LED0 output is used and (delay time)+ (PWM duty cycle)≤ 100 %)
Delay time = 10 %; PWM duty cycle = 20 % (LED on time = 20 %; LED off time = 80 %).
Delay time = 10 % = 409.6 ~ 410 counts = 19Ah.
Since the counter starts at 0 and ends at 4095, we will subtract 1, so delay time = 199h
counts.
LED0_ON_H = 1h; LED0_ON_L = 99h
LED on time = 20 % = 819.2 ~ 819 counts.
Off time = 4CCh (decimal 410+ 819−1= 1228)
LED0_OFF_H = 4h; LED0_OFF_L = CCh
Example 2: (assumes that the LED4 output is used and (delay time)+ (PWM duty cycle> 100 %)
Delay time = 90 %; PWM duty cycle = 90 % (LED on time = 90 %; LED off time = 10 %).
Delay time = 90 % = 3686.4~ 3686 counts− 1 = 3685 = E65h.
LED4_ON_H = Eh; LED4_ON_L = 65h
LED on time = 90 % = 3686 counts.
Since the delay time and LED on period of the duty cycle is greater than 4096 counts,
the LEDn_OFF count will occur in the next frame. Therefore, 4096 is subtracted from
the LEDn_OFF count to get the correct LEDn_OFF count. See Figure 9, Figure 10 and
Figure 11.
Off time = 4CBh (decimal 3685+ 3686 = 7372− 4096 = 3275)
LED4_OFF_H = 4h; LED4_OFF_L = CBh
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controllerNXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
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NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
Table 6. LED_ON, LED_OFF control registers (address 06h to 45h) bit descriptionLegend: * default value.
06h LED0_ON_L 7:0 LED0_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED0, 8 LSBs
07h LED0_ON_H 7:5 reserved R 000* non-writable LED0_ON_H[4] R/W 0* LED0 full ON
3:0 LED0_ON_H[3:0] R/W 0000* LEDn_ON count for LED0, 4 MSBs
08h LED0_OFF_L 7:0 LED0_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED0, 8 LSBs
09h LED0_OFF_H 7:5 reserved R 000* non-writable LED0_OFF_H[4] R/W 1* LED0 full OFF
3:0 LED0_OFF_H[3:0] R/W 0000*
0Ah LED1_ON_L 7:0 LED1_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED1, 8 LSBs
0Bh LED1_ON_H 7:5 reserved R 000* non-writable LED1_ON_H[4] R/W 0* LED1 full ON
3:0 LED1_ON_H[3:0] R/W 0000* LEDn_ON count for LED1, 4 MSBs
0Ch LED1_OFF_L 7:0 LED1_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED1, 8 LSBs
0Dh LED1_OFF_H 7:5 reserved R 000* non-writable LED1_OFF_H[4] R/W 1* LED1 full OFF
3:0 LED1_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED1, 4 MSBs
0Eh LED2_ON_L 7:0 LED2_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED2, 8 LSBs
0Fh LED2_ON_H 7:5 reserved R 000* non-writable LED2_ON_H[4] R/W 0* LED2 full ON
3:0 LED2_ON_H[3:0] R/W 0000* LEDn_ON count for LED2, 4 MSBs
10h LED2_OFF_L 7:0 LED2_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED2, 8 LSBs
11h LED2_OFF_H 7:5 reserved R 000* non-writable LED2_OFF_H[4] R/W 1* LED2 full OFF
3:0 LED2_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED2, 4 MSBs
12h LED3_ON_L 7:0 LED3_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED3, 8 LSBs
13h LED3_ON_H 7:5 reserved R 000* non-writable LED3_ON_H[4] R/W 0* LED3 full ON
3:0 LED3_ON_H[3:0] R/W 0000* LEDn_ON count for LED3, 4 MSBs
14h LED3_OFF_L 7:0 LED3_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED3, 8 LSBs
15h LED3_OFF_H 7:5 reserved R 000* non-writable LED3_OFF_H[4] R/W 1* LED3 full OFF
3:0 LED3_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED3, 4 MSBs
16h LED4_ON_L 7:0 LED4_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED4, 8 LSBs
17h LED4_ON_H 7:5 reserved R 000* non-writable LED4_ON_H[4] R/W 0* LED4 full ON
3:0 LED4_ON_H[3:0] R/W 0000* LEDn_ON count for LED4, 4 MSBs
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller18h LED4_OFF_L 7:0 LED4_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED4, 8 LSBs
19h LED4_OFF_H 7:5 reserved R 000* non-writable LED4_OFF_H[4] R/W 1* LED4 full OFF
3:0 LED4_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED4, 4 MSBs
1Ah LED5_ON_L 7:0 LED5_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED5, 8 LSBs
1Bh LED5_ON_H 7:5 reserved R 000* non-writable LED5_ON_H[4] R/W 0* LED5 full ON
3:0 LED5_ON_H[3:0] R/W 0000* LEDn_ON count for LED5, 4 MSBs
1Ch LED5_OFF_L 7:0 LED5_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED5, 8 LSBs
1Dh LED5_OFF_H 7:5 reserved R 000* non-writable LED5_OFF_H[4] R/W 1* LED5 full OFF
3:0 LED5_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED5, 4 MSBs
1Eh LED6_ON_L 7:0 LED6_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED6, 8 LSBs
1Fh LED6_ON_H 7:5 reserved R 000* non-writable LED6_ON_H[4] R/W 0* LED6 full ON
3:0 LED6_ON_H[3:0] R/W 0000* LEDn_ON count for LED6, 4 MSBs
20h LED6_OFF_L 7:0 LED6_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED6, 8 LSBs
21h LED6_OFF_H 7:5 reserved R 000* non-writable LED6_OFF_H[4] R/W 1* LED6 full OFF
3:0 LED6_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED6, 4 MSBs
22h LED7_ON_L 7:0 LED7_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED7, 8 LSBs
23h LED7_ON_H 7:5 reserved R 000* non-writable LED7_ON_H[4] R/W 0* LED7 full ON
3:0 LED7_ON_H[3:0] R/W 0000* LEDn_ON count for LED7, 4 MSBs
24h LED7_OFF_L 7:0 LED7_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED7, 8 LSBs
25h LED7_OFF_H 7:5 reserved R 000* non-writable LED7_OFF_H[4] R/W 1* LED7 full OFF
3:0 LED7_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED7, 4 MSBs
26h LED8_ON_L 7:0 LED8_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED8, 8 LSBs
27h LED8_ON_H 7:5 reserved R 000* non-writable LED8_ON_H[4] R/W 0* LED8 full ON
3:0 LED8_ON_H[3:0] R/W 0000* LEDn_ON count for LED8, 4 MSBs
28h LED8_OFF_L 7:0 LED8_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED8, 8 LSBs
29h LED8_OFF_H 7:5 reserved R 000* non-writable LED8_OFF_H[4] R/W 1* LED8 full OFF
3:0 LED8_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED8, 4 MSBs
Table 6. LED_ON, LED_OFF control registers (address 06h to 45h) bit description …continuedLegend: * default value.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller2Ah LED9_ON_L 7:0 LED9_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED9, 8 LSBs
2Bh LED9_ON_H 7:5 reserved R 000* non-writable LED9_ON_H[4] R/W 0* LED9 full ON
3:0 LED9_ON_H[3:0] R/W 0000* LEDn_ON count for LED9, 4 MSBs
2Ch LED9_OFF_L 7:0 LED9_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED9, 8 LSBs
2Dh LED9_OFF_H 7:5 reserved R 000* non-writable LED9_OFF_H[4] R/W 1* LED9 full OFF
3:0 LED9_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED9, 4 MSBs
2Eh LED10_ON_L 7:0 LED10_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED10, 8 LSBs
2Fh LED10_ON_H 7:5 reserved R 000* non-writable LED10_ON_H[4] R/W 0* LED10 full ON
3:0 LED10_ON_H[3:0] R/W 0000* LEDn_ON count for LED10, 4 MSBs
30h LED10_OFF_L 7:0 LED10_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED10, 8 LSBs
31h LED10_OFF_H 7:5 reserved R 000* non-writable LED10_OFF_H[4] R/W 1* LED10 full OFF
3:0 LED10_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED10, 4 MSBs
32h LED11_ON_L 7:0 LED11_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED11, 8 LSBs
33h LED11_ON_H 7:5 reserved R 000* non-writable LED11_ON_H[4] R/W 0* LED11 full ON
3:0 LED11_ON_H[3:0] R/W 0000* LEDn_ON count for LED11, 4 MSBs
34h LED11_OFF_L 7:0 LED11_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED11, 8 LSBs
35h LED11_OFF_H 7:5 reserved R 000* non-writable LED11_OFF_H[4] R/W 1* LED11 full OFF
3:0 LED11_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED11, 4 MSBs
36h LED12_ON_L 7:0 LED12_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED12, 8 LSBs
37h LED12_ON_H 7:5 reserved R 000* non-writable LED12_ON_H[4] R/W 0* LED12 full ON
3:0 LED12_ON_H[3:0] R/W 0000* LEDn_ON count for LED12, 4 MSBs
38h LED12_OFF_L 7:0 LED12_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED12, 8 LSBs
39h LED12_OFF_H 7:5 reserved R 000* non-writable LED12_OFF_H[4] R/W 1* LED12 full OFF
3:0 LED12_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED12, 4 MSBs
3Ah LED13_ON_L 7:0 LED13_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED13, 8 LSBs
3Bh LED13_ON_H 7:5 reserved R 000* non-writable LED13_ON_H[4] R/W 0* LED13 full ON
3:0 LED13_ON_H[3:0] R/W 0000* LEDn_ON count for LED13, 4 MSBs
Table 6. LED_ON, LED_OFF control registers (address 06h to 45h) bit description …continuedLegend: * default value.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controllerThe LEDn_ON_H output control bit 4, when set to logic 1, causes the output to be always
ON. The turning ON of the LED is delayed by the amount in the LEDn_ON registers.
LEDn_OFF[11:0] are ignored. When this bit= 0, then the LEDn_ON and LEDn_OFF
registers are used according to their normal definition.
The LEDn_OFF_H output control bit 4, when set to logic 1, causes the output to be
always OFF. In this case the values in the LEDn_ON registers are ignored.
Remark: When all LED outputs are configured as ‘always OFF’, the prescale counter and
all associated PWM cycle timing logic are disabled. If LEDn_ON_H[4] and
LEDn_OFF_H[4] are set at the same time, the LEDn_OFF_H[4] function takes
precedence.
3Ch LED13_OFF_L 7:0 LED13_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED13, 8 LSBs
3Dh LED13_OFF_H 7:5 reserved R 000* non-writable LED13_OFF_H[4] R/W 1* LED13 full OFF
3:0 LED13_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED13, 4 MSBs
3Eh LED14_ON_L 7:0 LED14_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED14, 8 LSBs
3Fh LED14_ON_H 7:5 reserved R 000* non-writable LED14_ON_H[4] R/W 0* LED14 full ON
3:0 LED14_ON_H[3:0] R/W 0000* LEDn_ON count for LED14, 4 MSBs
40h LED14_OFF_L 7:0 LED14_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED14, 8 LSBs
41h LED14_OFF_H 7:5 reserved R 000* non-writable LED14_OFF_H[4] R/W 1* LED14 full OFF
3:0 LED14_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED14, 4 MSBs
42h LED15_ON_L 7:0 LED15_ON_L[7:0] R/W 0000 0000* LEDn_ON count for LED15, 8 LSBs
43h LED15_ON_H 7:5 reserved R 000* non-writable LED15_ON_H[4] R/W 0* LED15 full ON
3:0 LED15_ON_H[3:0] R/W 0000* LEDn_ON count for LED15, 4 MSBs
44h LED15_OFF_L 7:0 LED15_OFF_L[7:0] R/W 0000 0000* LEDn_OFF count for LED15, 8 LSBs
45h LED15_OFF_H 7:5 reserved R 000* non-writable LED15_OFF_H[4] R/W 1* LED15 full OFF
3:0 LED15_OFF_H[3:0] R/W 0000* LEDn_OFF count for LED15, 4 MSBs
Table 6. LED_ON, LED_OFF control registers (address 06h to 45h) bit description …continuedLegend: * default value.
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.3.4 ALL_LED_ON and ALL_LED_OFF controlThe ALL_LED_ON and ALL_LED_OFF registers allow just four I2 C-bus write sequences
to fill all the ON and OFF registers with the same patterns.
The LEDn_ON and LEDn_OFF counts can vary from 0 to 4095. The LEDn_ON and
LEDn_OFF count registers should never be programmed with the same values.
Because the loading of the LEDn_ON and LEDn_OFF registers is via the I2 C-bus, and
asynchronous to the internal oscillator, we want to ensure that we do not see any visual
artifacts of changing the ON and OFF values. This is achieved by updating the changes at
the end of the LOW cycle.
7.3.5 PWM frequency PRE_SCALEThe hardware forces a minimum value that can be loaded into the PRE_SCALE register
at ‘3’. The PRE_SCALE register defines the frequency at which the outputs modulate. The
prescale value is determined with the formula shown in Equation1:
(1)
where the update rate is the output modulation frequency required. For example, for an
output frequency of 200 Hz with an oscillator clock frequency of 25 MHz:
(2)
The PRE_SCALE register can only be set when the SLEEP bit of MODE1 register is set to
logic1.
Table 7. ALL_LED_ON and ALL_LED_OFF control registers (address FAh to FEh) bit descriptionLegend: * default value.
FAh ALL_LED_ON_L 7:0 ALL_LED_ON_L[7:0] W only 0000 0000* LEDn_ON count for ALL_LED, 8 MSBs
FBh ALL_LED_ON_H 7:5 reserved R 000* non-writable ALL_LED_ON_H[4] W only 1* ALL_LED full ON
3:0 ALL_LED_ON_H[3:0] W only 0000* LEDn_ON count for ALL_LED, 4 MSBs
FCh ALL_LED_OFF_L 7:0 ALL_LED_OFF_L[7:0] W only 0000 0000* LEDn_OFF count for ALL_LED, MSBs
FDh ALL_LED_OFF_H 7:5 reserved R 000* non-writable ALL_LED_OFF_H[4] W only 1* ALL_LED full OFF
3:0 ALL_LED_OFF_H[3:0] W only 0000* LEDn_OFF count for ALL_LED, MSBs
FEh PRE_SCALE 7:0 PRE_SCALE[7:0] R/W 0001 1110* prescaler to program the output
frequency
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.3.6 SUBADR1 to SUBADR3, I2 C-bus subaddress 1 to 3Subaddresses are programmable through the I2 C-bus. Default power-up values are E2h,
E4h, E8h, and the device(s) will not acknowledge these addresses right after power-up
(the corresponding SUBx bit in MODE1 register is equal to 0).
Once subaddresses have been programmed to their right values, SUBx bits need to be
set to logic 1 in order to have the device acknowledging these addresses (MODE1
register).
Only the 7 MSBs representing the I2 C-bus subaddress are valid. The LSB in SUBADRx
register is a read-only bit (0).
When SUBx is set to logic 1, the corresponding I2 C-bus subaddress can be used during
either an I2 C-bus read or write sequence.
7.3.7 ALLCALLADR, LED All Call I2 C-bus addressThe LED All Call I2 C-bus address allows all the PCA9685s in the bus to be programmed
at the same time (ALLCALL bit in register MODE1 must be equal to 1 (power-up default
state)). This address is programmable through the I2 C-bus and can be used during either
an I2 C-bus read or write sequence. The register address can also be programmed as a
Sub Call.
Only the 7 MSBs representing the All Call I2 C-bus address are valid. The LSB in
ALLCALLADR register is a read-only bit (0).
If ALLCALL bit= 0, the device does not acknowledge the address programmed in register
ALLCALLADR.
Table 8. SUBADR1to SUBADR3 - I2 C-bus subaddress registers 0to 3 (address 02h to
04h) bit descriptionLegend: * default value.
02h SUBADR1 7:1 A1[7:1] R/W 1110 001* I2 C-bus subaddress 1 A1[0] R only 0* reserved
03h SUBADR2 7:1 A2[7:1] R/W 1110 010* I2 C-bus subaddress 2 A2[0] R only 0* reserved
04h SUBADR3 7:1 A3[7:1] R/W 1110 100* I2 C-bus subaddress 3 A3[0] R only 0* reserved
Table 9. ALLCALLADR - LED All Call I2 C-bus address register (address 05h) bit
descriptionLegend: * default value.
05h ALLCALLADR 7:1 AC[7:1] R/W 1110 000* ALLCALL I2 C-bus
address register AC[0] R only 0* reserved
NXP Semiconductors PCA9685
16-channel, 12-bit PWM Fm+ I2 C-bus LED controller
7.4 Active LOW output enable inputThe active LOW output enable (OE) pin, allows to enable or disable all the LED outputs at
the same time.
When a LOW level is applied to OE pin, all the LED outputs are enabled and follow
the output state defined in the LEDn_ON and LEDn_OFF registers with the polarity
defined by INVRT bit (MODE2 register).
When a HIGH level is applied to OE pin, all the LED outputs are programmed to the
value that is defined by OUTNE[1:0] in the MODE2 register.
The OE pin can be used as a synchronization signal to switch on/off several PCA9685
devices at the same time. This requires an external clock reference that provides blinking
period and the duty cycle.
The OE pin can also be used as an external dimming control signal. The frequency of the
external clock must be high enough not to be seen by the human eye, and the duty cycle
value determines the brightness of the LEDs.
7.5 Power-on resetWhen power is applied to VDD, an internal power-on reset holds the PCA9685 in a reset
condition until VDD has reached VPOR. At this point, the reset condition is released and the
PCA9685 registers and I2 C-bus state machine are initialized to their default states.
Thereafter, VDD must be lowered below 0.2 V to reset the device.
Table 10. LED outputs when OE =1000 1 1 if OUTDRV= 1, high-impedance if OUTDRV=0 0 high-impedance 1 high-impedance
