EL7520ILZ-T13 查看數據表（PDF） - Intersil

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EL7520ILZ-T13

4-Channel DC/DC Controller

Intersil 

EL7520, EL7520A

The minimum base-emitter resistor, RBL, can now be

calculated as:

RBL_min = VBE_max/(I_DRVL_min - Ic/Hfe_min) =

1.25V/(8mA - 500mA/100) = 417Ω

This is the minimum value that can be used - so, we now

choose a convenient value greater than this minimum value;

say 500Ω. Larger values may be used to reduce quiescent

current, however, regulation may be adversely affected, by

supply noise if RBL is made too high in value.

VBOOST

LX

0.9V

PG_LDOP +

-

+

-

GMP

LDO_ON

0.1µF

36V

ESD

CLAMP

CP (TO 36V)

RBP

7kΩ

DRVP

FBP

0.1µF

Q3

VON (TO 35V)

RP1

RP2

20kΩ

CON

1: Np

FIGURE 27. VON FUNCTIONAL BLOCK DIAGRAM

LX

0.1µF

PG_LDON -

+

0.4V

LDO_OFF

VREF

FBN

RN2

20kΩ

1: Nn

-

+

GMN

36V

ESD

CLAMP

RN1

DRVN

Q2

RBN

3kΩ

CP (TO -26V)

0.1µF

VOFF (TO -20V)

COFF

FIGURE 28. VOFF FUNCTIONAL BLOCK DIAGRAM

0.9V

PG_LDOL +

-

LDO_LOG

VIN OR VPROT

(3V TO 6V)

RBL

500Ω

DRVL

FBL

Q5 VLOGIC

(1.3V TO 3.6V)

CLOG

RL1

10µF

-

+

GML

1: N1

RL2

20kΩ

FIGURE 29. VLOGIC FUNCTIONAL BLOCK DIAGRAM

The VON power supply is used to power the positive supply

of the row driver in the LCD panel. The DC/DC consists of an

external diode-capacitor charge pump powered from the

inductor (LX) of the boost converter, followed by a low

dropout linear regulator (LDO_ON). The LDO_ON regulator

uses an external PNP transistor as the pass element. The

onboard LDO controller is a wide band (>10MHz)

transconductance amplifier capable of 4mA drive current,

which is sufficient for up to 40mA or more output current

under the low dropout condition (forced beta of 10). Typical

VON voltage supported by EL7520, EL7520A range from

+15V to +36V. A fault comparator is also included for

monitoring the output voltage. The under-voltage threshold

is set at 25% below the 1.2V reference.

The VOFF power supply is used to power the negative

supply of the row driver in the LCD panel. The DC/DC

consists of an external diode-capacitor charge pump

powered from the inductor (LX) of the boost converter,

followed by a low dropout linear regulator (LDO_OFF). The

LDO_OFF regulator uses an external NPN transistor as the

pass element. The onboard LDO controller is a wide band

(>10MHz) transconductance amplifier capable of 4mA drive

current, which is sufficient for up to 40mA or more output

current under the low dropout condition (forced beta of 10).

Typical VOFF voltage supported by EL7520, EL7520A range

from -5V to -20V. A fault comparator is also included for

monitoring the output voltage. The undervoltage threshold is

set at 200mV above the 0.2V reference level.

The VLOGIC power supply is used to power the logic circuitry

within the LCD panel. The DC/DC may be powered directly

from the low voltage input, 3.3V or 5.0V, or it may be powered

through the fault protection switch. The LDO_LOGIC regulator

uses an external PNP transistor as the pass element. The

onboard LDO controller is a wide band (>10MHz)

transconductance amplifier capable of 16mA drive current,

which is sufficient for up to 160mA or more output current

13

FN7318.0

July 12, 2005

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