Driving Method For Lcd Driver; When Using The Booster Circuit (Lcdcr<Bres>="1") - Toshiba TLCS-870/C Series Manual

15.2.3 Driving method for LCD driver

In the TMP86PM29BUG, LCD driving voltages can be generated using either an internal booster circuit or
an external resistor divider. This selection is made in LCDCR<BRES>.
15.2.3.1 When using the booster circuit (LCDCR<BRES>="1")
When the reference voltage is connected to the V1 pin, the booster circuit boosts the reference voltage
twofold (V2) or threefold (V3) to generate the output voltages for segment/common signals. When the
reference voltage is connected to the V2 pin, it is reduced to 1/2 (V1) or boosted to 3/2 (V3). When the
reference voltage is connected to the V3 pin, it is reduced to 1/3 (V1) or 2/3 (V2).
LCDCR<VFSEL> is used to select the reference frequency in the booster circuit. The faster the boost-
ing frequency, the higher the segment/common drive capability, but power consumption is increased.
Conversely, the slower the boosting frequency, the lower the segment/common drive capability, but power
consumption is reduced. If the drive capability is insufficient, the LCD may not be displayed clearly.
Therefore, select an optimum boosting frequency for the LCD panel to be used.
Table 15-3 shows the V3 pin current capacity and boosting frequency.
Note: When used as the booster circuit, bias should be composed to 1/3. Therefore, do not set
LCDCR<DUTY> to "10" or "11" when the booster circuit is enable (LCDCR<BRES>="1").
Keep the following
condition.
V 3
V 1 =
1/3 x V3
= 0.1 to 0.47 µF
C
Keep the following
condition.
V 3
V 2 =
2/3 x V3
= 0.1 to 0.47 µF
C
VDD
V3
C
V2
C
V1
C1
C
C0
VSS
a) Reference pin = V1
VDD
V3
C
V2
C
V1
C
C1
C
C0
VSS
b) Reference pin = V2
Page 157
TMP86PM29BUG
Reference voltage
Reference voltage