TS1102 datasheet(7/11 Pages) TOUCHSTONE

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TS1102

TS1102DS r1p0

Page 7

RTFDS

PIN FUNCTIONS

LABEL

FUNCTION

SOT23

RS+

External Sense Resistor Power-Side Connection

RS-

External Sense Resistor Load-Side Connection

1, 2

GND

Ground. Connect these pins to analog ground.

OUT

Output Voltage. VOUT is proportional to VSENSE = VRS+ - VRS-

BLOCK DIAGRAM

DESCRIPTION OF OPERATION

The internal configuration of the TS1102

– a

unidirectional high-side, current-sense amplifier - is

based on a commonly-used operational amplifier (op

amp) circuit for measuring load currents (in one

direction) in the presence of high-common-mode

voltages. In the general case, a current-sense

amplifier monitors the voltage caused by a load

current through an external sense resistor and

generates an output voltage as a function of that load

current. Referring to the typical application circuit on

Page 1, the inputs of the op-amp-based circuit are

connected across an external RSENSE resistor that

is used to measure load current. At the non-inverting

input of the TS1102 (the RS+ terminal), the applied

voltage is ILOAD x RSENSE. Since the RS- terminal is

the non-inverting input of the internal op amp, op-amp

feedback action forces the inverting input of the

internal

amp

the

same

potential

(ILOAD x RSENSE). Therefore, the voltage drop across

RSENSE (VSENSE) and the voltage drop across RGAIN

(at the RS+ terminal) are equal. To minimize any

additional error because of op-amp input bias current

mismatch, both RGAINs are the same value.

Since

the

internal

channel FET’s source is

connected to the inverting input of the internal op

amp and since the voltage drop across RGAIN is the

same as the external VSENSE, op amp feedback action

drives the gate of the FET such that the FET’s drain-

source current is equal to:

VSE SE

R A

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