PIC18F87K90 Datasheet, PDF (280/566 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt XLP Technology

PIC18F87K90 FAMILY
20.3.2 INTERNAL RESISTOR BIASING
This mode does not use external resistors, but rather
internal resistor ladders that are configured to generate
the bias voltage.
The internal reference ladder actually consists of three
separate ladders. Disabling the internal reference
ladder disconnects all of the ladders, allowing external
voltages to be supplied.
Depending on the total resistance of the resistor
ladders, the biasing can be classified as low, medium
or high power.
Table 20-3 shows the total resistance of each of the
ladders. Figure 20-4 shows the internal resister ladder
connections. When the internal resistor ladder is
selected, the bias voltage can either be from VDD or
from VDDCORE, depending on the LCDIRS setting.
TABLE 20-3: INTERNAL RESISTANCE
LADDER POWER MODES
Nominal
Power Mode Resistance of
IDD
Entire Ladder
Low
Medium
High
3 M
300 k
30 k
1 A
10 A
100 A
FIGURE 20-4:
LCD BIAS INTERNAL RESISTOR LADDER CONNECTION DIAGRAM
VVD_DDD
3x ^VB^Dan^Dd^COG^Rap^E
LCDIRS
LCDIRE
LCDCST<2:0>
VLCD3PE
LCDBIAS3
VLCD2PE
LCDBIAS2
VLCD1PE
LCDBIAS1
Low
Resistor
Ladder
Medium
Resistor
Ladder
High
Resistor
Ladder
A Power Mode
B Power Mode
LRLAT<2:0>
LRLAP<1:0>
LRLBP<1:0>
DS39957B-page 280
Preliminary
 2010 Microchip Technology Inc.