ADM8839ACPZ-REEL Просмотр технического описания (PDF) - Analog Devices

Номер в каталоге

Компоненты Описание

производитель

ADM8839ACPZ-REEL

Charge Pump Regulator for Color TFT Panels

Analog Devices 

ADM8839

THEORY OF OPERATION

POWER SEQUENCING

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 14.

VCC

SHDN

tR5V

90%

+5V

10%

tF5V

+15V

–15V

tR15V

90%

10%

tDELAY

90%

10%

tFM15V

–3V

Figure 14. Power Sequence

tF15V

tRM15V

TRANSIENT RESPONSE

The ADM8839 features extremely fast transient response,

making 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. Figure 11

and Figure 12 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 ±15 V output can deliver 150 μA of current in

the typical configuration, as shown in Figure 15. It is also

possible 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 a

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

−15 V outputs at any time (see Figure 16). In this configuration,

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

the functional block diagram (see Figure 1).

ADM8839

OSCILLATOR

LDO_ON/OFF

CONTROL

LOGIC

TIMING

GENERATOR

SHDN SHUTDOWN

CONTROL

C5, 2.2µF

VCC

VOLTAGE

DOUBLER

LDO

VOLTAGE

REGULATOR

DOUBLE

VOLTAGE

TRIPLER

TRIPLE

DISCHARGE

VOLTAGE

INVERTER

C1+

C1, 2.2µF

C1–

VOUT

LDO_IN

C6, 2.2µF

+5VOUT

+5VIN

C2+

+5V

C7, 2.2µF

C2, 0.22µF

C2–

C3+

C3– C3, 0.22µF

+15VOUT

+15V

C8, 0.22µF

C4+

C4, 0.22µF

C4–

GND

–15VOUT

–15V

C9, 0.22µF

Figure 15. 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 (µA)

Figure 16. +15 V/−15 V Output Voltage vs. Load Current,

Typical Configuration

Rev. C | Page 8 of 12

Share Link: