SC310 Просмотр технического описания (PDF) - Semtech Corporation

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SC310

High-Side Current-Sense Amplifier with Low Impedance Voltage Output

Semtech Corporation 

POWER MANAGEMENT

Block Diagram

SC310

VCC

CS+

CS-

SHDN

R4

Gain = A1

Gain = A2

Gain = A3

+

1k

A

Q1

R5

-

Gain = B

+

B

1k

-

R3

R1 20k

10k

R2 5k

Disable

OUT

GND

Detailed Description

SC310 is a unidirectional high-side current sense ampli-

fier for precision current monitoring. It has a wide com-

mon-mode range of 2.7 to 25V and allows high-side cur-

rent-sensing at voltages greater than supply voltage (VCC).

The SC310 operates as follows: Current from source (as

shown in the typical applications circuit on page. 1), flows

through RSENSE to the load. Since the inverting input of

amplifier A has a high input impedance, negligible cur-

rent flows through R5 (neglecting the input bias current).

Amplifier A has an inverting input voltage which equals

V(CS+) - ILOAD*RSENSE. The amplifier’s high open-loop gain

forces the non-inverting input voltage to the same volt-

age as the inverting input. The drop across R4 equals

ILOAD*RSENSE. Since IR4 flows through R4, IR4 =

(ILOAD*RSENSE)/R4. Resistor R3 then sets the overall gain

for amplifier A, A1, A2 or A3 (neglecting the input bias

currents for non-inverting inputs for amplifiers A and B).

The second amplifier, B, is a fixed gain stage (gain = B)

and the final output includes the gain obtained from this

stage.

The SC310 has three gain versions as follows:

Version

Gain Expression

Gain Value

SC310A

A1*B

20

SC310B

A2*B

50

SC310C

A3*B

100

 2005 Semtech Corp.

8

www.semtech.com

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