PCF8536AT datasheet(13/74 Pages) NXP

13 / 74 page

PCF8536

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Product data sheet

Rev. 2 — 21 February 2012

13 of 74

NXP Semiconductors

PCF8536

Universal LCD low multiplex driver with 6 channel PWM generator

8.1.5.1

Oscillator

The internal logic and LCD drive signals of the PCF8536 are timed either by the built-in

oscillator or from an external clock.

Internal clock: When the internal oscillator is used, all LCD and PWM signals are

generated from it. The oscillator runs at nominal 230 kHz. The relationship between this

frequency and the LCD frame frequency is detailed in Section 8.1.9. The relationship

between this frequency and the PWM frame frequency is detailed in Section 8.1.10.

Control over the internal oscillator is made with the OSC bit (see Section 8.1.5). The

internal oscillator is also switched on or off under certain combinations of modes which

are described in Table 13.

(1) Can only be used with the internal oscillator (OSC = 0).

(2) Can only be used with an external oscillator (OSC = 1).

(3) Nominal value for divide factor q is 24; source clock is 230 kHz (see Section 8.1.9).

(4) PWM requires an external or internal 230 kHz clock.

Fig 7.

Oscillator selection

Table 11.

Valid combinations of bits OSC, EFR, and COE

OSC

COE

EFR

OSCCLK pin

Clock source

not used

inactive;

may be left floating

internal oscillator used

not used

output of internal oscillator

frequency (prescaler)

internal oscillator used

not used

9.6 kHz input

OSCCLK pin

not used

230 kHz input

OSCCLK pin

Table 12.

Typical use of bits OSC, EFR, and COE

Usage

OSC

CDE

EFR

LCD and/or PWM with internal oscillator

not used

LCD and PWM with external oscillator

not used

LCD with external oscillator

not used

Internal oscillator

230 kHz

Programmable

divider

Programmable

divider

LCD waveform

generator

PWM waveform

generator

013aaa448

OSCCLK

LCD frame frequency

selection, q

PWM frame frequency

selection, p

EFR (2)

9.6 kHz (3)

OSC

COE (1)

(4)

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