EL5325A(2004) 데이터 시트보기 (PDF) - Intersil

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EL5325A
(Rev.:2004)

12-Channel TFT-LCD Reference Voltage Generator with External Shutdown

Intersil 

EL5325A

when sourcing, and:

PDMAX = VS × IS + Σ(VOUTi × ILOADi)

when sinking.

Where:

• i = 1 to total 12

• VS = Supply voltage

• IS = Quiescent current

• VOUTi = Output voltage of the i channel

• ILOADi = Load current of the i channel

By setting the two PDMAX equations equal to each other, we

can solve for the RLOADs to avoid the device overheat. The

package power dissipation curves provide a convenient way

to see if the device will overheat.

The EL5325A has an internal thermal shutdown circuitry that

prevents overheating of the part. When the junction

temperature goes up to about 150°C, the part will be

disabled. When the junction temperature drops down to

about 120°C, the part will be enabled. With this feature, any

short circuit at the outputs will enable the thermal shutdown

circuitry to disable the part.

POWER SUPPLY BYPASSING AND PRINTED CIRCUIT

BOARD LAYOUT

Good printed circuit board layout is necessary for optimum

performance. A low impedance and clean analog ground

plane should be used for the EL5325A. The traces from the

two ground pins to the ground plane must be very short. The

thermal pad of the EL5325A should be connected to the

analog ground plane. Lead length should be as short as

possible and all power supply pins must be well bypassed. A

0.1µF ceramic capacitor must be place very close to the VS,

VREFH, VREFL, and CAP pins. A 4.7µF local bypass

tantalum capacitor should be placed to the VS, VREFH, and

VREFL pins.

APPLICATION USING THE EL5325A

In the first application drawing, the schematic shows the

interconnect of a pair of EL5325A chips connected to give

12 gamma corrected voltages above the VCOM voltage, and

12 gamma corrected voltages below the VCOM voltage.

External Shutdown

The EL5325A also has an external shutdown to enable and

disable the part. The SHDN pin should never be driven low.

Rather, to enable the part, the SHDN pin must be left open

(float). To disable, the SHDN pin must be driven HI (>2V).

WIth this feature, the EL5325A can be forced to shut down,

regardless of any other conditions. A simple open collector

driver is adequate to control the enable and disable function:

VSD

R1

100K

R2

100K

SHDN

Q1

PNP

EL5325A

SHDN

9

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