ADE5166 datasheet(97/148 Pages) AD

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Preliminary Technical Data

ADE5166/ADE5169/ADE5566/ADE5569

Rev. PrB | Page 97 of 148

Table 92. LCD Data Memory Accessed Indirectly Through LCD Pointer SFR (LCDPTR, 0xAC) and LCD Data SFR (LCDDAT, 0xAE)1,2

LCD Pointer SFR (LCDPTR, 0xAC)

LCD Pointer SFR (LCDDAT, 0xAE)

LCD Memory Address

COM3

COM2

COM1

COM0

COM3

COM2

COM1

COM0

0x0E

FP28

0x0D

FP27

FP26

0x0C

FP25

FP24

0x0B

FP23

FP22

0x0A

FP21

FP20

0x09

FP19

FP18

0x08

FP17

FP16

0x07

FP15

FP14

0x06

FP13

FP12

0x05

FP11

FP10

0x04

FP9

FP8

0x03

FP7

FP6

0x02

FP5

FP4

0x01

FP3

FP2

0x00

FP1

FP0

1 COMx designates the common lines.

2 FPx designates the segment lines.

VOLTAGE GENERATION

The ADE5166/ADE5169/ADE5566/ADE5569 provide two ways

to generate the LCD waveform voltage levels. The on-chip

charge pump option can generate 5 V. This makes it possible to

use 5 V LCDs with the 3.3 V ADE5166/ADE5169/ADE5566/

ADE5569. There is also an option to use an external resistor ladder

with a 3.3 V LCD. The EXTRES bit in the LCD Configuration X

SFR (LCDCONX, 0x9C) selects the resistor ladder or charge

pump option.

When selecting how to generate the LCD waveform voltages,

the following should be considered:

•

Lifetime performance power consumption

•

Contrast control

Lifetime Performance Power Consumption

In most LCDs, a high amount of current is required when the LCD

waveforms change state. The external resistor ladder option draws a

constant amount of current, whereas the charge pump circuitry

allows dynamic current consumption. If the LCD module is used

with the internal charge pump option when the display is disabled,

the voltage generation is disabled, so that no power is consumed by

the LCD function. This feature results in significant power

savings if the display is turned off during battery operation.

Contrast Control

The electrical characteristics of the liquid in the LCD change

over temperature. This requires adjustments in the LCD waveform

voltages to ensure a readable display. An added benefit of the

internal charge pump voltage generation is a configurable bias

voltage that can be compensated over temperature and supply

to maintain contrast on the LCD. These compensations can be

performed based on the ADE5166/ADE5169/ADE5566/

ADE5569 temperature and supply voltage measurements (see

the Temperature, Battery, and Supply Voltage Measurements

section). This dynamic contrast control is not easily imple-

mented with external resistor ladder voltage generation.

The LCD bias voltage sets the contrast of the display when the

charge pump provides the LCD waveform voltages. The ADE5166/

ADE5169/ADE5566/ADE5569 provide 64 bias levels selected by

the BIASLVL bits in the LCD Configuration X SFR (LCDCONX,

0x9C). The voltage level on LCDVA, LCDVB and LCDVC depend

on the internal voltage reference value (VREF), BIASLVL[5:0]

selection, and the biasing selected as described in Table 83.

Lifetime Performance

DC offset on a segment degrades its performance over time.

The voltages generated through the internal charge pump

switch faster than those generated by the external resistor

ladder, reducing the likelihood of a dc voltage being applied

to a segment and increasing the lifetime of the LCD.

LCD EXTERNAL CIRCUITRY

The voltage generation selection is made by Bit EXTRES in

the LCD Configuration X SFR (LCDCONX, 0x9C). This bit is

cleared by default for charge pump voltage generation, but can

be set to enable an external resistor ladder.

Charge Pump

Voltage generation through the charge pump requires external

capacitors to store charge. The external connections to LCDVA,

LCDVB, and LCDVC, as well as LCDVP1 and LCDVP2, are

shown in Figure 68.

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