TMP86FS28DFG datasheet(209/272 Pages) TOSHIBA

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Page 197

TMP86FS28DFG

16.2.3 Driving method for LCD driver

In the TMP86FS28DFG, LCD driving voltages can be generated using either an internal booster circuit or an

external resistor divider. This selection is made in LCDCR<BRES>.

16.2.3.1 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 16-3 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").

VDD

VSS

Keep the following

condition.

V1 =

Reference voltage

= 0.1 to 0.47

µF

1/3 x V3

a) Reference pin = V1

VDD

VSS

Keep the following

condition.

V2 =

Reference voltage

= 0.1 to 0.47

µF

b) Reference pin = V2

2/3 x V3

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