PCA9685 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet Rev. 4 — 16 April 2015 14 of 52
NXP Semiconductors
PCA9685
16-channel, 12-bit PWM Fm+ I
2
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 s 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 s 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 5. MODE1 - Mode register 1 (address 00h) bit description
Legend: * default value.
Bit Symbol Access Value Description
7 RESTART R Shows state of RESTART logic. See Section 7.3.1.1
for detail.
W 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.
0* Restart disabled.
1 Restart enabled.
6 EXTCLK R/W To use the EXTCLK pin, this bit must be set by the following sequence:
1. Set the SLEEP bit in MODE1. This turns off the internal oscillator.
2. 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.
0* Use internal clock.
1 Use EXTCLK pin clock.
5 AI R/W 0* Register Auto-Increment disabled
[1]
.
1 Register Auto-Increment enabled.
4 SLEEP R/W 0 Normal mode
[2]
.
1* Low power mode. Oscillator off
[3][4]
.
3 SUB1 R/W 0* PCA9685 does not respond to I
2
C-bus subaddress 1.
1 PCA9685 responds to I
2
C-bus subaddress 1.
2 SUB2 R/W 0* PCA9685 does not respond to I
2
C-bus subaddress 2.
1 PCA9685 responds to I
2
C-bus subaddress 2.
1 SUB3 R/W 0* PCA9685 does not respond to I
2
C-bus subaddress 3.
1 PCA9685 responds to I
2
C-bus subaddress 3.
0 ALLCALL R/W 0 PCA9685 does not respond to LED All Call I
2
C-bus address.
1* PCA9685 responds to LED All Call I
2
C-bus address.
refresh_rate
EXTCLK
4096 prescale 1+
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=
