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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

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

STOP

0

4095 0

4095 0

4095 0

example 1

LEDn_ON

LEDn_OFF

819

1228

Fig 7. LED output, example 1

819

1228

819

1228

819

1228

002aad812

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

STOP

0

example 2

LEDn_ON

LEDn_OFF

4095 0

3686

Fig 8. LED output, example 2

4095 0

3686

3275

4095 0

3686

3275

002aad813

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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