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 2005 Semtech Corp.

www.semtech.com

POWER MANAGEMENT

SC310

Block Diagram

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 (V

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+) - I

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

age as the inverting input. The drop across R4 equals

I

Since I

(I

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.

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The SC310 has three gain versions as follows:

VCC

+

-

+

-

R1

R2

R3

R4

R5

Q1

A

B

Gain = A1

Gain = A2

Gain = A3

Gain = B

CS-

GND

SHDN

CS+

OUT

1k

10k

20k

5k

1k

Disable