PCF8578T/1 NXP Semiconductors, PCF8578T/1 Datasheet - Page 16

• Manufacturer Part Number: PCF8578T/1
• Description: IC, LCD DRIVER, ROW/COLUMN, 56VSOP
• Manufacturer: NXP Semiconductors

Specifications of PCF8578T/1

• Supply Current: 20µA
• No. Of Digits / Alpha: 36
• Meter Display Type: LCD
• Supply Voltage Range: 2.5V To 6V
• Driver Case Style: VSOP
• No. Of Pins: 56
• Operating Temperature Range: -40°C To +85°C
• Base: RoHS Compliant
• No. Of Segments: 384
• Interface Type: I2C
• Rohs Compliant: Yes

NXP Semiconductors
PCF8578_6
Product data sheet
8.5.1 Internal clock
8.5.2 External clock
8.5 Oscillator
8.6 Timing generator
The clock signal for the system may be generated by the internal oscillator and prescaler.
The frequency is determined by the value of the resistor R
normal use a value of 330 k is recommended. The clock signal, for cascaded
PCF8579s, is output at CLK and has a frequency of
or
If an external clock is used, OSC must be connected to V
to CLK.
Table 8.
[1]
[2]
The timing generator of the PCF8578 organizes the internal data flow of the device and
generates the LCD frame synchronization pulse SYNC, whose period is an integer
multiple of the clock period. In cascaded applications, this signal maintains the correct
timing relationship between the PCF8578 and PCF8579s in the system.
Oscillator frequency,
f
12288
12288
osc
Fig 10. Oscillator frequency as a function of external oscillator resistor, R
1
8
A clock signal must always be present, otherwise the LCD may be frozen in a DC state.
R
(Hz)
ext(OSC)
(multiplex rate 1:24) of the oscillator frequency.
Table 8
[2]
To avoid capacitive coupling, which could adversely affect oscillator stability, R
placed as closely as possible to the OSC pin. If this proves to be a problem, a filtering capacitor
may be connected in parallel to R
Signal frequencies required for nominal 64 Hz frame frequency
= 330 k .
summarizes the nominal CLK and SYNC frequencies.
(kHz)
f
Frame frequency,
f
64
64
osc
fr
10
10
10
Rev. 06 — 5 May 2009
1
(Hz)
3
2
10
LCD row/column driver for dot matrix graphic displays
ext(OSC)
10
2
Multiplex rate,
(1:n)
1:8, 1:16, 1:32 6
1:24
.
10
3
R
1
ext(OSC)
6
(multiplex rate 1:8, 1:16 and 1:32)
Division ratio Clock frequency,
8
DD
msa837
ext(OSC)
(k )
and the external clock signal
10
4
, see
PCF8578
Figure
© NXP B.V. 2009. All rights reserved.
[1]
f
2048
1536
ext(OSC)
clk
ext(OSC)
(Hz)
10. For
should be
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