PCF8576DHSLASH2 datasheet(25/41 Pages) PHILIPS

25 / 41 page

2004 Dec 22

Philips Semiconductors

Product speciﬁcation

Universal LCD driver for low

multiplex rates

PCF8576D

All PCF8576Ds connected in cascade are correctly

synchronized by the SYNC signal. This synchronization is

guaranteed after the Power-on reset. The only time that

SYNC is likely to be needed is if synchronization is lost

accidentally, for example, by noise in adverse electrical

environments, or if the LCD multiplex drive mode is

changed in an application using several cascaded

PCF8576Ds, as the drive mode cannot be changed on all

of the cascaded devices simultaneously. SYNC can be

either an input or an output signal; a SYNC output is

implemented as an open-drain driver with an internal

pull-up resistor. A PCF8576D asserts SYNC at the start of

its last active backplane signal, and monitors the SYNC

line at all other times. If cascade synchronization is lost, it

will be restored by the first PCF8576D to assert SYNC.

The timing relationship between the backplane waveforms

and the SYNC signal for each LCD drive mode is shown in

Fig.20.

Table 14 SYNC contact resistance

The contact resistance between the SYNC input/output on

each cascaded device must be controlled. If the resistance

is too high, the device will not be able to synchronize

properly; this is particularly applicable to chip-on-glass

applications. The maximum SYNC contact resistance

allowed for the number of devices in cascade is given in

Table 14.

NUMBER OF DEVICES

MAXIMUM CONTACT

RESISTANCE

6000

Ω

3 to 5

2200

Ω

6 to 10

1200

Ω

10 to 16

700

Ω

handbook, full pagewidth

HOST

MICRO-

PROCESSOR/

MICRO-

CONTROLLER

SDA

SCL

CLK

OSC

SYNC

1, 58, 59

2, 3

40 segment drives

4 backplanes

40 segment drives

LCD PANEL

(up to 2560

elements)

PCF8576DU

SA0

VDD

VLCD

LCD

MDB077

SDA

SCL

SYNC

CLK

OSC

1, 58, 59

613

2, 3

BP0 to BP3

(open-circuit)

SA0 VSS

VSS

VDD

VLCD

PCF8576DU

BP0 to BP3

2CB

≤

Fig.19 Cascaded PCF8576D configuration.

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