ADM666 데이터 시트보기 (PDF) - Analog Devices

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ADM666

+5 V Fixed, Adjustable Micropower Linear Voltage Regulators

Analog Devices 

DIP & SOIC PIN CONFIGURATIONS

SENSE 1

8 VIN

VOUT2 2 ADM663 7 VTC

VOUT1 3 TOP VIEW 6 VSET

(Not to Scale)

GND 4

5 SHDN

SENSE 1

8 VIN

VOUT 2 ADM666 7 LBO

LBI 3 TOP VIEW 6 VSET

(Not to Scale)

GND 4

5 SHDN

ADM663/ADM666

PIN FUNCTION DESCRIPTION

Mnemonic Function

VOUT(1) (2)

VIN

SENSE

GND

LBI

LBO

SHDN

VSET

VTC

Voltage Regulator Output(s)

Voltage Regulator Input

Current Limit Sense Input. (Referenced to

VOUT(2).) If not used it should be connected to

VOUT(2)

Ground Pin. Must be connected to 0 V

Low Battery Detect Input. Compared with 1.3 V

Low Battery Detect Output. Open Drain Output

Digital Input. May be used to disable the device

so that the power consumption is minimized

Voltage Setting Input. Connect to GND for +5 V

output or connect to resistive divider for adjust

able output

Temperature-Proportional Voltage for negative

TC Output

GENERAL INFORMATION

The ADM663/ADM666 contains a micropower bandgap refer-

ence voltage source, an error amplifier A1, two comparators

C1, C2 and a series pass output transistor. A P-channel FET

and an NPN transistor are used on the ADM663 while the

ADM666 uses an NPN output transistor.

CIRCUIT DESCRIPTION

The internal bandgap reference is trimmed to 1.3 V ± 30 mV.

This is used as a reference input to the error amplifier A1. The

feedback signal from the regulator output is supplied to the

other input by an on-chip voltage divider or by two external re-

sistors. When VSET is at ground, the internal divider provides

the error amplifier’s feedback signal giving a +5 V output. When

VSET is at more than 50 mV above ground, the error amplifier's

input is switched directly to the VSET pin, and external resistors

are used to set the output voltage. The external resistors are

selected so that the desired output voltage gives 1.3 V at VSET.

Comparator C1 monitors the output current via the SENSE

input. This input, referenced to VOUT(2), monitors the voltage

drop across a load sense resistor. If the voltage drop exceeds

0.5 V, then the error amplifier A1 is disabled and the output

current is limited.

The ADM663 has an additional amplifier, A2, which provides a

temperature-proportional output, VTC. If this is summed into

the inverting input of the error amplifier, a negative temperature

coefficient results at the output. This is useful when powering

liquid crystal displays over wide temperature ranges.

The ADM666 has an additional comparator, C3 which com-

pares the voltage on the Low Battery Input, LBI, pin to the in-

ternal +1.3 V reference. The output from the comparator drives

an open drain FET connected to the Low Battery Output pin,

LBO. The Low Battery Threshold may be set using a suitable

voltage divider connected to LBI. When the voltage on LBI falls

below 1.3 V, the open drain output LBO is pulled low.

Both the ADM663 and the ADM666 contain a shutdown

(SHDN) input which can be used to disable the error amplifier

and hence the voltage output. The quiescent current in shut-

down is less than 12 µA.

ADM663

VIN

VOUT2

VOUT1

0.5V

C1

SENSE

A1

SHDN

50mV

C2

VSET

GND

1.3V 0.9V A2

VTC

REF

Figure 1. ADM663 Functional Block Diagram

REV. 0

–3–

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