PCF8545 datasheet(21/72 Pages) NXP

21 / 72 page

PCF8545

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Product data sheet

Rev. 1 — 13 November 2013

21 of 72

NXP Semiconductors

PCF8545

Universal LCD driver for multiplex rates up to 1:8

The host microcontroller maintains the two line I2C-bus or a three line SPI-bus

communication channel with the PCF8545. 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, VLCD) and the LCD panel

selected for the application.

The minimum recommended values for external capacitors on VDD and VLCD are 100 nF

respectively. Decoupling of VLCD helps to reduce display artifacts. The decoupling

capacitors should be placed close to the IC with short connections to the respective

supply pin and VSS.

8.4 LCD voltage selector

The LCD voltage selector coordinates the multiplexing of the LCD in accordance with the

selected LCD drive configuration. The operation of the voltage selector is controlled by the

set-bias-mode command (see Table 16) and the set-MUX-mode command (see

Table 15).

Fractional LCD biasing voltages are obtained from an internal voltage divider. The biasing

configurations that apply to the preferred modes of operation, together with the biasing

characteristics as functions of VLCD and the resulting discrimination ratios (D), are given in

Table 23.

Fig 11. Typical system configuration for the I2C-bus

Fig 12. Typical system configuration for the SPI-bus

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