PCF85176 datasheet(6/43 Pages) NXP

6 / 43 page

PCF85176_1

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Product data sheet

Rev. 01 — 14 April 2010

6 of 43

NXP Semiconductors

PCF85176

Universal LCD driver for low multiplex rates

Functional description

The PCF85176 is a versatile peripheral device designed to interface any

microprocessor or microcontroller with a wide variety of LCDs. It can directly drive any

static or multiplexed LCD containing up to four backplanes and up to 40 segments.

The possible display configurations of the PCF85176 depend on the number of active

backplane outputs required. A selection of display configurations is shown in Table 4. All

of these configurations can be implemented in the typical system shown in Figure 4.

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

channel with the PCF85176. The internal oscillator is enabled by connecting

pin OSC to pin VSS. The appropriate biasing voltages for the multiplexed LCD waveforms

are generated internally. The only other connections required to complete the system are

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

7.1 Power-On Reset (POR)

At power-on the PCF85176 resets to the following starting conditions:

• 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)

Table 4.

Display configurations

Number of:

7-segment alphanumeric

14-segment alphanumeric

Dot matrix

Backplanes

Elements

Digits

Indicator symbols

Characters

Indicator symbols

160

160 dots (4

× 40)

120

120 dots (3

× 40)

80 dots (2

× 40)

40 dots (1

× 40)

The resistance of the power lines must be kept to a minimum.

Fig 4.

Typical system configuration

HOST

MICRO-

PROCESSOR/

MICRO-

CONTROLLER

2CB

SDA

SCL

OSC

40 segment drives

4 backplanes

LCD PANEL

(up to 160

elements)

PCF85176

SA0

VDD

VSS

VDD

VLCD

013aaa071

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