PCA9620 datasheet(14/71 Pages) NXP

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PCA9620

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Product data sheet

Rev. 1 — 9 December 2010

14 of 71

NXP Semiconductors

PCA9620

Universal LCD driver for low multiplex rates

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

channel with the PCA9620. 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 (VDD1, VDD2, VSS, VLCD), the external capacitors, and the

LCD panel selected for the application.

The minimum recommended values for external capacitors on VDD1, VDD2, and VLCD are

nominal 100 nF. When using bigger capacitors, especially on the VLCD, the generated

ripple will be consequently smaller, however it will take longer for the internal charge pump

to first reach the target VLCD voltage.

In the case that VDD1 and VDD2 are connected externally, the capacitors on VDD1 and VDD2

can be replaced by a single capacitor with a minimum value of 200 nF.

Remark: In the case of insufficient decoupling, ripple of VDD1 and VDD2 will create

additional VLCD ripple. The ripple on VLCD can be reduced by making the VSS connection

as low-ohmic as possible. Excessive ripple on VLCD may give rise to flicker on the display.

7.3 Start-up and shut-down

7.3.1 Power-On Reset (POR)

At power-on the PCA9620 resets to starting conditions as follows:

1. All backplane outputs are set to VSS.

2. All segment outputs are set to VSS.

3. Selected drive mode is: 1:8 with 1

⁄

4 bias.

4. Input and output bank selectors are reset.

5. The I2C-bus interface is initialized.

6. The data pointer is cleared (set logic 0).

7. The Internal oscillator is running; no clock signal is available on pin CLK; pin CLK is in

3-state.

8. Temperature measurement is enabled.

VDD1 from 2.5 V to 5.5 V, VDD2 from 2.5 V to 5.5 V and VLCD from 2.5 V to 9.0 V.

Fig 5.

Typical system configuration when using an external VLCD

HOST

PROCESSOR/

MICRO-

CONTROLLER

≤

2Cb

SDA

SCL

60 segment drives

8 backplanes

LCD PANEL

(up to 480

elements)

PCA9620

VDD1

VSS

013aaa248

VLCD

VDD2

VDD1

CLK

n.c.

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