ADE5166 datasheet(98/148 Pages) AD

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ADE5166/ADE5169/ADE5566/ADE5569

Preliminary Technical Data

Rev. PrB | Page 98 of 148

LCDVC

LCDVB

LCDVA

LCDVP1

LCDVP2

CHARGE PUMP

AND

LCD WAVEFORM

CIRCUITRY

100nF

470nF

Figure 68. External Circuitry for Charge Pump Option

External Resistor Ladder

To enable the external resistor ladder option, set the EXTRES

bit in the LCD Configuration X SFR (LCDCONX, 0x9C). When

EXTRES = 1, the LCD waveform voltages are supplied by the

external resistor ladder. Because the LCD voltages are not

generated on-chip, the LCD bias compensation implemented to

maintain contrast over temperature and supply is not possible.

The external circuitry needed for the resistor ladder option is

shown in Figure 69. The resistors required should be in the

range of 10 kΩ to 100 kΩ and based on the current required by

the LCD being used.

LCDVC

LCDVB

LCDVA

LCDVP1

LCDVP2

LCD WAVEFORM

CIRCUITRY

Figure 69. External Circuitry for External Resistor Ladder Option

LCD FUNCTION IN PSM2

The LCDPSM2 and LCDEN bits in the LCD configuration SFR

(LCDCON, 0x95) control LCD functionality in the PSM2

operating mode (see Table 93).

Note that the internal voltage reference must be enabled by

setting the REF_BAT_EN bit in the peripheral configuration

SFR (PERIPH, 0xF4) to allow LCD operation in PSM2 (see

Table 19).

Table 93. Bits Controlling LCD Functionality in PSM2 Mode

LCDPSM2

LCDEN

Result

The display is off in PSM2.

The display is on in PSM2.

The display is off in PSM2.

In addition, note that the LCD configuration and data memory

is retained when the display is turned off.

Example LCD Setup

An example of how to set up the LCD peripheral for a specific

LCD is described in this section with the following parameters:

•

Type of LCD: 5 V, 4× multiplexed with 1/3 bias, 96 segment

•

Voltage generation: internal charge pump

•

Refresh rate: 64 Hz

A 96-segment LCD with 4× multiplexing requires 96/4 = 24

segment lines. Sixteen pins, FP0 to FP15, are automatically

dedicated for use as LCD segments. Eight more pins must be

chosen for the LCD function. Because the LCD has 4× multi-

plexing, all four common lines are used. As a result, COM2/FP28

and COM3/FP27 cannot be used as segment lines. Based on the

alternate functions of the pins used for FP16 through FP25,

FP16 to FP23 are chosen for the eight remaining segment lines.

These pins are enabled for LCD functionality in the LCD

segment enable SFR (LCDSEGE, 0x97) and LCD Segment

Enable 2 SFR (LCDSEGE2, 0xED).

To determine contrast setting for this 5 V LCD, Table 83 shows

the BIASLVL[5:0] setting that corresponds to a VC of 5 V in

1/3 bias mode. The maximum bias level setting for this LCD is

BIASLVL[5:0] = 101110.

The LCD is set up with the following 8052 code:

; set up LCD pins to have LCD functionality

MOV

LCDSEG,#FP20EN+FP21EN+FP22EN+FP23EN

MOV

LCDSEGX,#FP16EN+FP17EN+FP18EN+FP19EN

; set up LCDCON for fLCDCLK=2048Hz, 1/3 bias

and 4x multiplexing

MOV

LCDCON,#BIAS+LMUX1+LMUX0

; set up LCDCONX for charge pump and

BIASLVL[110111]

MOV

LCDCONX,#BIASLVL5+BIASLVL4+BIASLVL3+BI

ASLVL2+BIASLVL1+BIASLVL0

; set up refresh rate for 64Hz with fLCDCLK =

2048 Hz

MOV

LCDCLK,#FD3+FD2+FD1+FD0

; set up LCD data registers with data to be

displayed using

; LCDPTR and LCDDATA registers

; turn all segments on FP27 ON and FP26 OFF

ORL

LCDCONY,#01h

; start data memory

refresh

MOV

LCDDAT,#F0H

MOV

LCDPTR, #80h OR 0DH

ANL

LCDCONY,#0FEh ; end of data memory

refresh

ORL

LCDCON,#LCDEN ; enable LCD

To set up the same 3.3 V LCD for use with an external resistor

ladder,

; setup LCDCONX for external resistor ladder

MOV

LCDCONX,#EXTRES

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