pcf8576d NXP Semiconductors, pcf8576d Datasheet - Page 25

• Manufacturer Part Number: pcf8576d
• Description: Universal Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

Philips Semiconductors
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.
2004 Dec 22
handbook, full pagewidth
Universal LCD driver for low
multiplex rates
V SS
V LCD
V DD
CONTROLLER
PROCESSOR/
MICRO-
MICRO-
HOST
R
2C B
t r
Fig.19 Cascaded PCF8576D configuration.
SYNC
SDA
OSC
SCL
CLK
SYNC
SDA
SCL
CLK
OSC
4
5
7
1, 58, 59
2, 3
8
A0
1, 58, 59
2, 3
4
5
7
8
6
PCF8576DU
A0
V
9
DD
A1
25
PCF8576DU
6
9
V DD
A1
10
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.
2
3 to 5
6 to 10
10 to 16
A2
13
10
NUMBER OF DEVICES
V
A2 SA0 V SS
13
11
LCD
SA0
V LCD
11
12
V SS
12
40 segment drives
4 backplanes
40 segment drives
BP0 to BP3
BP0 to BP3
(open-circuit)
6000
2200
1200
700
LCD PANEL
(up to 2560
elements)
MAXIMUM CONTACT
MDB077
RESISTANCE
Product specification
PCF8576D