PCA9633_5 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 05 — 25 July 2008 20 of 43
NXP Semiconductors
PCA9633
4-bit Fm+ I
2
C-bus LED driver
7.8 Individual brightness control with group dimming/blinking
A 97 kHz fixed frequency signal with programmable duty cycle (8 bits, 256 steps) is used
to control individually the brightness for each LED.
On top of this signal, one of the following signals can be superimposed (this signal can be
applied to the 4 LED outputs):
• A lower 190 Hz fixed frequency signal with programmable duty cycle (8 bits,
256 steps) is used to provide a global brightness control.
• A programmable frequency signal from 24 Hz to
1
⁄
10.73
Hz (8 bits, 256 steps) with
programmable duty cycle (8 bits, 256 steps) is used to provide a global blinking
control.
Minimum pulse width for LEDn Brightness Control is 40 ns.
Minimum pulse width for Group Dimming is 20.48 µs.
When M = 1 (GRPPWM register value), the resulting LEDn Brightness Control + Group Dimming signal will have 2 pulses of
the LED Brightness Control signal (pulse width = N × 40 ns, with ‘N’ defined in PWMx register).
This resulting Brightness + Group Dimming signal above shows a resulting Control signal with M = 4 (8 pulses).
Fig 11. Brightness + Group Dimming signals
123456789101112 507
508
509
510
511
512
1234567891011
Brightness Control signal (LEDn)
M × 256 × 2 × 40 ns
with M = (0 to 255)
(GRPPWM Register)
N × 40 ns
with N = (0 to 255)
(PWMx Register)
256 × 40 ns = 10.24 µs
(97.6 kHz)
1234567812345678
Group Dimming signal
resulting Brightness + Group Dimming signal
256 × 2 × 256 × 40 ns = 5.24 ms (190.7 Hz)
002aab417
