PCF8532 datasheet(5/44 Pages) NXP

5 / 44 page

PCF8532_1

Product data sheet

Rev. 1 — 10 February 2009

5 of 44

NXP Semiconductors

PCF8532

Universal LCD driver for low multiplex rates

The host microprocessor or microcontroller maintains the 2-line I2C-bus communication

channel with the PCF8532.

Biasing voltages for the multiplexed LCD waveforms are generated internally, removing

the need for an external bias generator. The internal oscillator is selected by connecting

pin OSC to VSS. The only other connections required to complete the system are the

power supplies (VDD, VSS and VLCD) and the LCD panel selected for the application.

7.1 Power-on reset

At power-on the PCF8532 resets to a default starting condition:

• All backplane and segment outputs are set to VLCD

• The selected drive mode is 1:4 multiplex with 1

⁄

3 bias

• Blinking is switched off

• Input and output bank selectors are reset

• The I2C-bus interface is initialized

• The data pointer and the subaddress counter are cleared (set to logic 0)

• The display is disabled

• If internal oscillator is selected (OSC pin connected to VSS), then there is no clock

signal on pin CLK

Do not transfer data on the I2C-bus after a power-on for at least 1 ms to allow the reset

action to complete.

7.2 LCD bias generator

Fractional LCD biasing voltages are obtained from an internal voltage divider of three

series resistors connected between VLCD and VSS. The center resistor can be switched

out of the circuit to provide a 1

⁄

2 bias voltage level for the 1:2 multiplex conﬁguration.

Fig 3.

Typical system conﬁguration

HOST

MICRO-

PROCESSOR/

MICRO-

CONTROLLER

2CB

SDA

SDAACK

SCL

OSC

160 segment drives

4 backplanes

LCD PANEL

(up to 640

elements)

PCF8532

SA0

VDD

VSS

VDD

VLCD

001aah852

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