HM17CM256 datasheet(38/111 Pages) HYNIX

38 / 111 page

HM17CM256

- 38 -

This block generates the voltages necessary for driving LCD panel. The power supply circuit

consists of voltage boosting circuit and voltage converting circuit and generates the voltages (VLCD,

V1, V2, V3, V4. ) for LCD driving.

For large panel driving, it’s preferable to use external voltage source rather than to use built-in

power supply circuit for good image quality.

When using external voltage source, disable the built-in power supply circuit(AMPON, DCON=‘00’),

supply the VLCD, V1, V2, V3, V4 and VOUT externally and open the C1+, C1-, C2+, C2-, C3+, C3-, C4+, C4-,

C5+, C5-, C6+, C6-, VREF, VREG, VEE terminals.

According to power supply circuit control command input, the power supply circuit can be enabled

partially.

External power supply and partial inner power circuit can be used together.

Refer to the

next table.

DCON

AMPON

Boosting circuit

Converting circuit

External voltage input

remark

Disable

disable

VOUT, VLCD, V1, V2, V3, V4 common

1,3

Disable

enable

VOUT common

2,3

Enable

enable

−

1. All the built-in boosting circuit, converting circuit is not used. Open the ,C1+, C1-, C2+, C2-, C3+, C3-, C4+,

C4-, C5+, C5-, C6+, C6-, VREF, VREG, VEE terminals, LCD driving voltage should be applied externally.

2.Only the Boosting circuit is not used. Open the C1+,C1-,C2+,C2-,C3+,C3-,C4+,C4-,C5+,C5-,C6+,C6-, VOUT

terminals, The power for converting circuit must be supplied through VOUT terminal and the reference

voltage must be supplied by VREF terminal.

3.The conditions between VOUT, VLCD, V1, V2, V3, and V4

are

VOUT

≥ V

LCD

≥ V

SS.

(23) VOLTAGE BOOSTING CIRCUIT

By connecting capacitor CA1 between C1+ and C1-, C2+ and C2-, C3+ and C3-, C4+ and C4-, C5+

and C5- , C6+ and C6-, VOUT and VSS , n-time boosted voltage of VEE - VSS can be generated through

VOUT port.

The boosting coefficient can be set by command and 2-times/ 3-times / 4-times/ 5-

times/ 6-times/ 7-times boosted voltage is output through VOUT port.

At application, specific boosting coefficient is used, refer to the following description.

At 2-times boosting is designed, connect boosting capacitor CA1 between C1+ and C1- , and

open C2+, C2-, C3+, C3-, C4+, C4-, C5+, C5-, C6+, C6- terminals.

At 3-times boosting is designed, connect boosting capacitor CA1 between C1+ and C1- , C2+

and C2- , and open C3+,C3-, C4+, C4-, C5+, C5-, C6+, C6-

terminals.

At 4-times boosting is designed, connect boosting capacitor CA1 between C1+ and C1- , C2+

and C2- , C3+ and C3- , and open C4+, C4-, C5+, C5-, C6+, C6- terminals

At 5-times/ 6-times/ 7-times boosting are same structures with upper case.

Special care should be taken so that the voltage of VOUT would not exceed 18V MAX.

VOUT voltage exceeding 18V can cause malfunction and reliability problem.

3-times boosting

7-times boosting

VSS=0V

VEE=3V

VOUT=9V

VOUT=17.5V

VSS=0V

VEE=2.5V

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