PCA9635 Datasheet, PDF (18/35 Pages) NXP Semiconductors – 16-bit Fm+ I2C-bus LED driver

NXP Semiconductors
PCA9635
16-bit Fm+ I²C-bus LED driver
Table 15. Output transistors based on LEDOUT registers, INVRT and OUTDRV bits when OE = 0^[1] …continued
LEDOUT
INVRT
11
0
individual +
group
dimming/blinking 0
OUTDRV
0
1
Upper transistor
(V_DD to LEDn)
off
Lower transistor
(LEDn to V_SS)
individual + group
PWM
(non-inverted)
LEDn state
V_SS or high-Z^[2] = PWMx or GRPPWM
values
individual PWM
(non-inverted)
individual PWM
(non-inverted)
V_SS or V_DD = PWMx or GRPPWM values
1
0
off
individual + group high-Z^[2] or V_SS = (1 − PWMx) or
PWM (inverted) (1 − GRPPWM) values
1
1
individual PWM
(inverted)
individual PWM
(inverted)
V_DD or V_SS = (1 − PWMx) or
(1 − GRPPWM) values
[1] When OE = 1, LED output state is controlled only by OUTNE[1:0] bits (MODE2 register).
[2] External pull-up or LED current limiting resistor connects LEDn to V_DD.
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 ¹â„_10.73 Hz (8 bits, 256 steps) with
programmable duty cycle (8 bits, 256 steps) is used to provide a global blinking
control.
1 2 3 4 5 6 7 8 9 10 11 12
508 510 512
507 509 511 1 2 3 4 5 6 7 8 9 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)
Group Dimming signal
256 × 2 × 256 × 40 ns = 5.24 ms (190.7 Hz)
12345678
12345678
resulting Brightness + Group Dimming signal
002aab417
Fig 6.
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).
Brightness + Group Dimming signals
PCA9635_6
Product data sheet
Rev. 06 — 11 September 2008
© NXP B.V. 2008. All rights reserved.
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