Datasheet

TSC1031 Application information
Doc ID 16875 Rev 2 19/26
7 Application information
The TSC1031 can be used to measure current and to feed back the information to a
microcontroller.
Figure 22. Typical application
The current from the supply flows to the load through the R
sense
resistor causing a voltage
drop equal to V
sense
across R
sense
. The amplifier’s input currents are negligible, therefore its
inverting input voltage is equal to V
m
. The amplifier's open-loop gain forces its non-inverting
input to the same voltage as the inverting input. As a consequence, the amplifier adjusts
current flowing through Rg1 so that the voltage drop across Rg1 exactly matches V
sense
.
Therefore, the drop across R
g1
is:
V
Rg1
=V
sense
=R
sense
.I
load
If I
Rg1
is the current flowing through R
g1
, then I
Rg1
is given by the formula:
I
Rg1
=V
sense
/R
g1
The I
Rg1
current flows is multiplied by a ratio K2 and the resulting current flows into resistor
R
g3
. Therefore, the voltage drop on the R
g3
resistor can be calculated as follows.
V
Rg3
=R
g3
.K2.I
Rg1
=(R
g3
/R
g1
).K2.V
sense
=K1.K2.V
sense
with K1=R
g3
/R
g1
=10.
The voltage across the R
g3
resistor is buffered to the Out pin by the voltage buffer, featuring
a gain equal to 2. Therefore V
out
can be expressed as:
V
out
= 2.K1.K2.V
sense
= Av .V
sense
with Av= 2.K1.K2
or: V
out
= Av .R
sense
.I
load
Common-mode voltage: 2.9 V to 70 V
AM06157
5 V
Vsense
Vout
load
Iload
Rsense
Vp Vm
Out
Rg1
5K
Rg2
Current
multiplier
Sense
amplifier
Vcc+
TSC1031
A1
Vcc-
K2
2.5 or 5
µ
Controller
ADC
Vcc
Gnd
SEL
GPIO
Rg3
50K
x2
Rf2Rf1
Rf3
Gnd