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PCA9685BS

16-channel, 12-bit PWM Fm+ I2C-bus LED controller

NXP Semiconductors. 

NXP Semiconductors

PCA9685

16-channel, 12-bit PWM Fm+ I2C-bus LED controller

7.3.1 Mode register 1, MODE1

Table 4. 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.

refresh_rate = -4--0---9---6-----×--E---(-X-p---T-r--e-C--s--L-c---aK---l--e-----+----1----)

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

1*

3

SUB1

R/W

0*

Normal mode[2].

Low power mode. Oscillator off[3][4].

PCA9685 does not respond to I2C-bus subaddress 1.

2

SUB2

1

R/W

0*

1

PCA9685 responds to I2C-bus subaddress 1.

PCA9685 does not respond to I2C-bus subaddress 2.

PCA9685 responds to I2C-bus subaddress 2.

1

SUB3

R/W

0*

1

0

ALLCALL R/W

0

PCA9685 does not respond to I2C-bus subaddress 3.

PCA9685 responds to I2C-bus subaddress 3.

PCA9685 does not respond to LED All Call I2C-bus address.

1*

PCA9685 responds to LED All Call I2C-bus address.

[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.

PCA9685

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 3 — 2 September 2010

© NXP B.V. 2010. All rights reserved.

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