Datasheet

PCA8536 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 2 — 21 February 2012 45 of 74
NXP Semiconductors
PCA8536
Automotive LCD low multiplex driver with 6 channel PWM generator
8.11.2 PWM inversion mode
The PWM inversion mode can be enabled by setting the PWMI bit to logic 1 (see Table 7
on page 8). The PWMI mode will invert the PWM waveform.
By default, all PWM outputs will switch HIGH at the same time. If the PWM output is used
to drive external LEDs then this could cause a voltage dip on the power supply of the
LEDs. With the PWMI mode, it is possible to prevent multiple outputs switching HIGH at
the same time by ensuring that the PWM values are not identical.
In the example in Figure 30
, none of the six PWM outputs switch HIGH together. All PWM
channels instead switch off together; however this will not cause any power supply
disturbances.
When PWM inversion mode is used, the PWM duty cycle can be calculated with:
(10)
Fig 30. PWM example waveforms for PWMI = 1
001aan570
f
PWM
PWM register 0 = 0
100.00 %
99.20 %
75.00 %
50.00 %
25.00 %
0.78 %
PWM register 1 = 1
PWM register 2 = 32
PWM register 3 = 64
PWM register 4 = 96
PWM register 5 = 127
1
t =
128 x f
PWM
DutyCycle
128 PWMvalue–
128
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100=