MC141531 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC141531

LCD Segment / Common Driver CMOS

Motorola => Freescale 

Display Timing Generator

This module is an on chip low power RC oscillator circuitry (Fig-

ure 6). The oscillator frequency can be selected in the range of

15kHz to 50kHz by external resistor. One can enable the circuitry by

software command. For external clock provided, feed the clock to

OSC2 and leave OSC1 open.

Annunciator Control Circuit

The LCD waveform of the 3 annunciators and BP are generated

by this module. The 3 independent annunciators are enabled by soft-

ware command. Annunciator is also controlled by oscillator circuit.

Before turning the annunciators on, the oscillator must be on in

advance. Annunciator output waveform shown in Figure 7.

Internal Oscillator selected

enable1 enable2

Oscillation Circuit

OSC1

OSC2

Oscillator enable

enable

Buffer

MC141531

External component

Feedback for internal oscillator

For external CLK input

Figure 6. Oscillator Circuitry

BP

ANNUN1

ANNUN2

ANNUN1

ANNUN2

OSC

ON / OFF

ON / OFF

DISABLE

ON

OFF

ENABLE

ON

ON

ENABLE

ON

ON

ENABLE

ON

OFF

ENABLE

DVDD

DVSS

DVDD

DVSS

DVDD

DVSS

ON / OFF

ON / OFF

DISABLE

Figure 7. Annunciators and BP Display Waveform

LCD Driving Internal DC/DC Converter and Regulator

This module generates the LCD voltage needed for display output. It

takes a single supply input and generate necessary bias voltages. It

consists of :

1. Voltage Doubler and Voltage Tripler

To generate the Vcc voltage. Either Doubler or Tripler can be

enabled.

2. Voltage Regulator

Feedback gain control for initial LCD voltage. It can also be used with

external contrast control.

3. Voltage Divider

Divide the LCD display voltage (VLL2-VLL6) from the regulator output.

This is a low power consumption circuit which can save the most dis-

play current compare with traditional resistor ladder method.

4. Self adjust temperature compensation circuitry

Provide 4 different compensation grade selections to satisfy the vari-

ous liquid crystal temperature grades. The grading can be selected

by software control.

5. Contrast Control Block

Software control of 16 voltage levels of LCD voltage.

All blocks can be individually turned off if external DC/DC Converter

is employed.

17 Bit Latch / 120 Bit Latch

A 137 bit long register which carry the display signal information.

First 17 bits are Common driving signals and other 120 bits are Seg-

ment driving signals. Data will be input to the HV-buffer Cell for bump-

ing up to the required level.

Level Selector

Level Selector is a control of the display synchronization. Display

voltage can be separated into two sets and used with different cycles.

Synchronization is important since it selects the required LCD voltage

level to the HV Buffer Cell for output signal voltage pump.

HV Buffer Cell (Level Shifter)

HV Buffer Cell works as a level shifter which translates the low volt-

age output signal to the required driving voltage. The output is shifted

out with an internal FRM clock which comes from the Display Timing

Generator. The voltage levels are given by the level selector which is

synchronized with the internal M signal.

MC141531

3–150

MOTOROLA

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