PIC16F/LF1946/47
26.4.2
POWER MODES
26.4 LCD Bias Internal Reference
Ladder
The internal reference ladder may be operated in one of
three power modes. This allows the user to trade off LCD
contrast for power in the specific application. The larger
the LCD glass, the more capacitance is present on a
physical LCD segment, requiring more current to
maintain the same contrast level.
The internal reference ladder can be used to divide the
LCD bias voltage two or three equally spaced voltages
that will be supplied to the LCD segment pins. To create
this, the reference ladder consists of three matched
resistors. Refer to Figure 26-3.
Three different power modes are available, LP, MP and
HP. The internal reference ladder can also be turned off
for applications that wish to provide an external ladder
or to minimize power consumption. Disabling the
internal reference ladder results in all of the ladders
being disconnected, allowing external voltages to be
supplied.
26.4.1
BIAS MODE INTERACTION
When in 1/2 Bias mode (BIASMD = 1), then the middle
resistor of the ladder is shorted out so that only two
voltages are generated. The current consumption of the
ladder is higher in this mode, with the one resistor
removed.
Whenever the LCD module is inactive (LCDA = 0), the
internal reference ladder will be turned off.
TABLE 26-3:
LCD INTERNAL LADDER
POWER MODES (1/3 BIAS)
Power
Mode
Nominal Resistance of
Entire Ladder
Nominal
IDD
Low
3 Mohm
300 kohm
30 kohm
1 µA
10 µA
100 µA
Medium
High
DS41414A-page 336
Preliminary
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
