PCA9625_2

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 02 — 15 January 2008

16 of 33

NXP Semiconductors

PCA9625

7.7 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):

256 steps) is used to provide a global brightness control.

⁄

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 6.

Brightness + Group Dimming signals

123456789

10 11 12

507

508

509

510

511

512

123456789

10 11

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)

12345678

12345678

Group Dimming signal

resulting Brightness + Group Dimming signal

256

× 2 × 256 × 40 ns = 5.24 ms (190.7 Hz)

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