Datasheet

PIC18F97J94 FAMILY
DS30575A-page 254  2012 Microchip Technology Inc.
13.5.1 AUTOMATIC POWER MODE
SWITCHING
As an LCD segment is electrically only a capacitor, cur-
rent is drawn only during the interval when the voltage
is switching. To minimize total device current, the LCD
reference ladder can be operated in a different power
mode for the transition portion of the duration. This is
controlled by the LCDREFH/L registers.
Mode A Power mode is active for a programmable
time, beginning at the time when the LCD segment
waveform is transitioning. The LRLAT<2:0> bits
(LCDREFL<2:0>) select how long or if the Mode A is
active. Mode B Power mode is active for the remaining
time before the segments or commons change again.
As shown in Figure 13-4, there are 32 counts in a single
segment time. Type-A can be chosen during the time
when the wave form is in transition. Type-B can be
used when the clock is stable or not in transition.
By using this feature of automatic power switching
using Type-A/Type-B, the power consumption can be
optimized for a given contrast.
FIGURE 13-4: LCD REFERENCE LADDER POWER MODE SWITCHING DIAGRAM
Single Segment Time
'H00 'H01 'H02 'H03 'H04 'H05 'H06 'H07 'H1E 'H1F 'H00 'H01
'H3
Power Mode A Power Mode B Mode A
LRLAT<2:0>
lcd_32x_clk
cnt<4:0>
lcd_clk
LRLAT<2:0>
Segment Data
Power Mode