pca9685 NXP Semiconductors, pca9685 Datasheet - Page 16

• Manufacturer Part Number: pca9685
• Description: 16-channel, 12-bit Pwm Fm+ I 2c-bus Led Controller
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9685_1
Product data sheet
Fig 7.
Fig 8.
LEDn_OFF
LEDn_OFF
example 1
LEDn_ON
example 2
LEDn_ON
STOP
STOP
LED output, example 1
LED output, example 2
0
0
819
1228
Example 1: (assumes that the LED0 output is used and
(delay time) + (PWM duty cycle)
Example 2: (assumes that the LED4 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.
LED on time = 20 % = 819.2 ~ 819 counts.
Off time = 4CCh (decimal 410 + 819
Delay time = 90 %; PWM duty cycle = 90 % (LED on time = 90 %; LED off time = 10 %).
Delay time = 90 % = 3686.4 ~ 3686 counts
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
Off time = 4CBh (decimal 3685 + 3686 = 7372
LED0_ON_H = 1h; LED0_ON_L = 99h
LED0_OFF_H = 4h; LED0_OFF_L = CCh
LED4_ON_H = Eh; LED4_ON_L = 65h
LED4_OFF_H = 4h; LED4_OFF_L = CBh
11.
4095 0
4095 0
3686
819
Rev. 01 — 24 July 2008
1228
16-channel, 12-bit PWM Fm+ I
100 %)
3275
4095 0
4095 0
3686
1 = 1228)
1 = 3685 = E65h.
819
4096 = 3275)
1228
Figure
2
C-bus LED controller
3275
4095 0
4095 0
3686
PCA9685
© NXP B.V. 2008. All rights reserved.
9,
Figure 10
819
002aad812
002aad813
1228
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