ade7169f16 Analog Devices, Inc., ade7169f16 Datasheet - Page 94

• Manufacturer Part Number: ade7169f16
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc And Lcd Driver
• Manufacturer: Analog Devices, Inc.

ADE7169F16
waveform voltage levels. The on-chip charge pump option can
generate 5V. This makes it possible to use 5V LCDs with the
3.3V ADE7169F16. There is also an option to use an external
resistor ladder with a 3.3V 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:
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 will result in significant power savings if the display is
turned off in battery operation.
Contrast control
The electrical characteristics of the liquid in the LCD change
over temperature, requiring 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 ADE7169F16 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
ADE7169F16 provides 64 bias levels selectable using the BLVL
bits in the LCD Configuration X SFR (LCDCONX, 0x9C). The
voltage level on LCDVA, LCDVB and LCDVC depend on the
the Interntal voltage reference value (Vref), BLVL[5:0] selection
and the biasing selected as described in Table 73.
Lifetime Performance
DC offset on a segment will degrade 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.
Power Consumption
Contrast Control
Lifetime Performance
Rev. PrD | Page 94 of 140
LCD EXTERNAL CIRCUITRY
The voltage generation selection is made by bit EXTRES in the
LCD Configuration X SFR (LCDCONX, 0x9C). This bit is clear
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 VA, VB,
and VC as well as VP1 and VP2 are shown in LCD
Configuration X SFR (LCDCONX, 0x9C).
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. Since the LCD voltages are not being
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 64. The resistors required should be in the
range of 10k to 100k and based on the current required by the
LCD being used.
LCD FUNCTION IN PSM2
The LCDPSM2 bit in the LCD Configuration SFR (LCDCON,
0x95) and the LCDEN bit in the LCD Configuration SFR
LCD Waveform
LCD Waveform
Charge Pump
Figure 64: External circuitry for External Resistor Ladder option
Circuitry
Circuitry
and
Figure 63: External circuitry for Charge Pump option
Preliminary Technical Data
LCDVC
LCDVB
LCDVA
LCDVP1
LCDVP2
LCDVC
LCDVB
LCDVA
LCDVP1
LCDVP2
100nF
470nF
470nF
470nF