Datasheet

ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569
Rev. B | Page 105 of 152
Table 99. LCD Data Memory Accessed Indirectly Through LCD Pointer SFR (LCDPTR, Address 0xAC) and LCD Data SFR (LCDDAT,
Address 0xAE)
1, 2
LCD Pointer SFR (LCDPTR, Address 0xAC) LCD Pointer SFR (LCDDAT, Address 0xAE)
LCD Memory Address COM3 COM2 COM1 COM0 COM3 COM2 COM1 COM0
0x0E FP28 FP28 FP28 FP28
0x0D FP27 FP27 FP27 FP27 FP26 FP26 FP26 FP26
0x0C FP25 FP25 FP25 FP25 FP24 FP24 FP24 FP24
0x0B FP23 FP23 FP23 FP23 FP22 FP22 FP22 FP22
0x0A FP21 FP21 FP21 FP21 FP20 FP20 FP20 FP20
0x09 FP19 FP19 FP19 FP19 FP18 FP18 FP18 FP18
0x08 FP17 FP17 FP17 FP17 FP16 FP16 FP16 FP16
0x07 FP15 FP15 FP15 FP15 FP14 FP14 FP14 FP14
0x06 FP13 FP13 FP13 FP13 FP12 FP12 FP12 FP12
0x05 FP11 FP11 FP11 FP11 FP10 FP10 FP10 FP10
0x04 FP9 FP9 FP9 FP9 FP8 FP8 FP8 FP8
0x03 FP7 FP7 FP7 FP7 FP6 FP6 FP6 FP6
0x02 FP5 FP5 FP5 FP5 FP4 FP4 FP4 FP4
0x01 FP3 FP3 FP3 FP3 FP2 FP2 FP2 FP2
0x00 FP1 FP1 FP1 FP1 FP0 FP0 FP0 FP0
1
COMx designates the common lines.
2
FPx designates the segment lines.
VOLTAGE GENERATION
The ADE7166/ADE7169/ADE7566/ADE7569 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 ADE7166/ADE7169/ADE7566/ADE7569.
There is also an option to use an external resistor ladder with a
3.3 V LCD. The EXTRES bit (Bit 6) in the LCD Configuration X
SFR (LCDCONX, Address 0x9C) selects the resistor ladder or
charge pump option. In the ADE7116 only, the resistor driver
option is available.
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 ADE7166/ADE7169/ADE7566/
ADE7569 temperature and supply voltage measurements (see
the Temperature, Battery, and Supply Voltage Measurements
section). This dynamic contrast control is not easily implemented
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
ADE7166/ADE7169/ADE7566/ADE7569 provide 64 bias levels
selected by the BIASLVL[5:0] bits in the LCD Configuration X
SFR (LCDCONX, Address 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 90.
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.