ay0438 Microchip Technology Inc., ay0438 Datasheet - Page 3

• Manufacturer Part Number: ay0438
• Description: 32-segment Cmos Lcd Driver
• Manufacturer: Microchip Technology Inc.

1.3
LCD can be driven by an external signal or by con-
necting a capacitor between LCD and ground (GND),
which will enable the on-chip oscillator required to gen-
erate the backplane output voltage. Figure 5 shows the
relationship between capacitance value and output fre-
quency. Leaving the LCD input unconnected is not
recommended. When driven by an external clock, the
backplane output is in phase with the input clock. When
cascading
Figure 7), the backplane output can be generated
using a capacitor to GND on the first AY0438. This
backplane output can then be connected to the LCD
input of the second AY0438. The backplane output of
the second device is then used to drive the backplane
of the LCD module.
FIGURE 6: CASCADING TWO AY0438 DEVICES
FIGURE 7: CASCADE TIMING DIAGRAM
1995 Microchip Technology Inc.
Data out
CLOCK
Data in
Clock
Load
Data
Load
in
LCD
two
LCD
AY0438
Clock
Load
Generator
LCD AC
START
devices
32-bit Static Shift Register
32 Segment Drivers
1
(Figure 6
32 Latches
SEG 64
Backplane
output
and
Data
out
1 to 32
Outputs
LCD
FIGURE 5: OSCILLATOR FREQUENCY
Data
in
140
120
100
80
60
40
Clock
Load
Generator
63
LCD AC
0
1/f
SEG 2
GRAPH (TYPICAL @ 25 C)
20
32-bit Static Shift Register
32 Segment Drivers
40
32 Latches
CL (pF)
64
60
t
DS
SEG 1
Backplane
output
t
80
PD
AY0438
t
DH
DS70010I-page 3
100
t
PW
33 to 64
Outputs
Data
out
120