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PCA9685_2
NXP B.V. 2009. All rights reserved.
Product data sheet
Rev. 02 — 16 July 2009
16 of 50
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
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
Off time = 4CBh (decimal 3685 + 3686 = 7372
4096 = 3275)
LED4_OFF_H = 4h; LED4_OFF_L = CBh
Fig 7.
LED output, example 1
0
STOP
example 1
LEDn_ON
LEDn_OFF
4095 0
819
1228
4095 0
002aad812
819
1228
819
1228
819
1228
Fig 8.
LED output, example 2
0
STOP
example 2
LEDn_ON
LEDn_OFF
4095 0
3686
4095 0
002aad813
3275
3686
3275
3686