UPD16686 datasheet(39/102 Pages) RENESAS

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Data Sheet S15548EJ1V0DS

µµµµPD16686, 16687

3.6 Power Supply Circuit

3.6.1 Power supply circuit

The power supply circuit supplies the voltage needed to drive the LCD. It includes a booster, voltage regulator, and

voltage follower.

In the power supply circuit, the power system control 1 (R32) is used to control the ON/OFF status of the power supply

circuit's booster, voltage regulator (also called V regulator), and voltage follower (V/F). This makes it possible to jointly use

an external power supply together with certain functions of the on-chip power supply. Table 3-7 shows the function that

controls the 3-bit data in the power system control 1 (R32) and Table 3-7 shows a reference chart of combinations.

Table 3-7. Control Values of Bits in Power System Control 1

Status

Item

OP2

Booster control bit

OFF

OP1

Voltage regulator (V regulator) control bit

OFF

OP0

Voltage follower (V/F) control bit

OFF

Table 3-8. Reference Chart of Combinations

External

Use Status

OP2 OP1 OP0

Booster

V Regulator

V/F

Power Supply

Input

Boost-Related

System Pins

<1> Use on-chip power supply

enable

VDD2

Used

<2> Use V regulator and V/F only

disable

enable

VOUT

Not connected

<3> Use V/F only

disable

enable

VOUT, AMPOUT

Not connected

<4> Use external power supply

disable

VOUT,

Not connected

only

VLCD to VLC4

Caution The boost-related system pins are indicated as pins C1

+, C1−−−− to C9+, C9−−−−, and C1A.

3.6.2 Booster

A booster that boosts the LCD driving voltage by 2 to 9 times is incorporated in the power supply circuit.

Since the booster uses signals from the on-chip oscillator, either the oscillator must be operating or a display clock must be

input from an external source.

The booster uses pins C1

+, C1−−−− to C9+, C9−−−− for normal boost and pins C1A and VDD2 for boost regulation. The wire

impedance should be kept as low as possible. The number of boost levels is set using the FBS2, FBS1, and FBS0 flags in

power system control 3 (R34), as shown in Table 3-9.

Caution If a capacitor is connected to a boost-related system pin that is not for one of these set boost levels,

current consumption may increase. Therefore, do not connect any capacitors beyond the number of

set boost levels. This also applies for the CA1 pin, used to regulate the boost levels.

Figure 3-12 describes the connection method for boost levels and capacitors.

The partial booster is settings are made using the BST1 and BST0 flags in the power system control 3 (R34), as shown in

Table 3-10.

UPD16686 Datasheet(PDF) 39 Page - Renesas Technology Corp

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