ADM8839ACP(RevA) 데이터 시트보기 (PDF) - Analog Devices

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ADM8839ACP
(Rev.:RevA)

Charge Pump Regulator for Color TFT Panels

Analog Devices 

ADM8839

POWER SEQUENCING

In order for the TFT panel to power up correctly, the gate drive

supplies must be sequenced such that the –15 V supply is up

before the +15 V supply. The ADM8839 controls this sequence.

When the device is turned on (a logic high on SHDN), the

ADM8839 allows the –15 V output to ramp immediately but

holds off the +15 V output. It continues to do this until the

negative output has reached –3 V. At this point, the positive

output is enabled and allowed to ramp to +15 V. This sequence

is highlighted in Figure 1.

VCC

SHDN

tR5V

90%

+5V

10%

tF5V

+15V

–15V

tR15V

90%

10%

tDELAY

90%

–3V

10%

tFM15V

Figure 1. Power Sequence

tF15V

tRM15V

TRANSIENT RESPONSE

The ADM8839 features extremely fast transient response, mak-

ing it very suitable for fast image updates on TFT LCD panels.

This means that even under changing load conditions, there is

still very effective regulation of the 5 V output. TPCs 9 and 10

show how the 5 V output responds when a maximum load is

dynamically connected and disconnected. Note that the output

settles within 5 µs to less than 1% of the output level.

BOOSTING THE CURRENT DRIVE OF THE ؎15 V SUPPLY

The ADM8839 Ϯ15 V output can deliver 150 µA of current in

the typical configuration, as shown in Figure 2. It is also pos-

sible to draw 100 µA from the +15 V output and 200 µA from

the –15 V output, or vice versa. It is possible to draw only a

maximum of 300 µA combined from both the +15 V and the

–15 V outputs at any time (see Figure 3). In this configuration,

+5VOUT (Pin 4) is connected to +5VIN (Pin 5), as shown in

the Functional Block Diagram.

ADM8839

OSCILLATOR

LDO_ON/OFF

CONTROL

LOGIC

TIMING

GENERATOR

SHDN SHUTDOWN

CONTROL

C5, 2.2␮F

VCC

VOLTAGE

DOUBLER

LDO

VOLTAGE

REGULATOR

DOUBLE

VOLTAGE

TRIPLER

TRIPLE

DISCHARGE

VOLTAGE

INVERTER

C1+

C1, 2.2␮F

C1–

VOUT

LDO_IN

C6, 2.2␮F

+5VOUT

+5VIN

C2+

+5V

C7, 2.2␮F

C2, 0.22␮F

C2–

C3+

C3– C3, 0.22␮F

+15VOUT

+15V

C8, 0.22␮F

C4+

C4, 0.22␮F

C4–

GND

–15VOUT

–15V

C9, 0.22␮F

Figure 2. Typical Configuration

15.1

15.0

14.9

14.8

+15V AT 25؇C

14.7

14.6

14.5

–15V AT 25؇C

14.4

14.3

14.2

14.1

0

50

100

150

200

ILOAD – ␮A

Figure 3. +15 V/–15 V Output Voltage vs. Load

Current, Typical Configuration

REV. A

–7–

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