AMC7834 Datasheet, PDF (37/93 Pages) Texas Instruments – AMC7834 12-Bit Integrated Power-Amplifier Monitor and Control System with Temperature, Current and Voltage Supervision Capabilities

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AMC7834
SLAS972B – NOVEMBER 2014 – REVISED MARCH 2016
7.3.4 Current Sensors
The AMC7834 device integrates four unidirectional high-side current-sense amplifiers that amplify a small
differential voltage developed across a current-sense resistor in the presence of high-input common-mode
voltages. The AMC7834 current-sense amplifiers accept input signals with a common-mode voltage range from 4
V to 60 V. Each amplifier can operate with differential voltages up to 200 mV.
As shown in Figure 51, current flowing through R_SENSE develops a voltage drop, V_SENSE. The voltage across the
sense resistor, V_SENSE, is applied to one of the AMC7834 current-sense amplifier inputs. The current sense
inputs should be connected as closely as possible to the shunt resistor to minimize any resistance in series with
the shunt resistance.
4 V to 60 V
I_SENSE
R_SENSE
To Load
AMC7834
V_SENSE
SENSE±
SENSE+
ADC
12-b
Figure 51. AMC7834 Current-Sense Amplifier
The accuracy of the current measurement depends heavily on the accuracy of the shunt resistor, R_(SENSE). The
use of a Kelvin sense resistor is highly recommended (see Figure 52).
Sense Resistor
Current Flow
from Supply
Current Flow
to Load
SENSE+
SENSE±
AMC7834
Figure 52. Kelvin Connection to the Sense Resistor
The sense-resistor value is application dependent and is typically a compromise between small-signal accuracy,
maximum permissible voltage drop, and allowable power dissipation in the current measurement circuit. For best
results, the value of the resistor is calculated from the maximum-expected load current, I_Lmax, and the maximum
differential voltage supported by the current-sense amplifier (200 mV). High values of R_(SENSE) provide better
accuracy at lower currents by minimizing the effects of the current-sense amplifier offset. Low values of R_(SENSE)
minimize load voltage loss, but at the expense of low current accuracy. In general, a compromise between low
current accuracy and load circuit losses must be made.
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