SI8540 Datasheet, PDF (7/18 Pages) List of Unclassifed Manufacturers – HIGH-SIDE CURRENT SENSE AMPLIFIER

Si8540
3. Functional Description
The Si8540 is designed to operate over an input common-mode range of 5 to 36 V. Figure 2 shows an example
Si8540 application with external sense resistor, R_SENSE, external current gain-setting resistors, R_G1 and R_G2, and
output scaling resistor, R_OUT. The supply current flowing into the Si8540 inverting and non-inverting inputs (R_G1,
R_G2) is negligible compared to I_LOAD and, as a result, has no appreciable effect on measurement accuracy. The
internal current sense amplifier measures the differential input voltage, V_SENSE, and generates an output current
proportional to I_LOAD. Resistor R_OUT converts this current to a voltage, and its value determines the output signal
gain. The Si8540 is placed in a low-power shutdown mode when SHDN is at V_IH.
SOURCE
RSENSE
Si8540
RG1
RG1
RG2
RG2
+_
LOAD
ILOAD
SHDN
Control
GND
OUT
V_OUT
R_OUT
I_OUT
Figure 2. Si8540 Application Circuit
3.1. Application Information
The Si8540 can sense a wide range of currents with different sense resistor values. Table 3 lists typical operational
values.
Table 3. Recommended Current Sense Resistor for a Given Full-Scale Load Current
Full-scale
Load
Current
I_SENSE (A)
0.1
1
5
10
Current-
Sense
Resistor
R_SENSE (m)
Gain-Setting
Resistors,
RG1 = RG2 ()
1000
200
100
200
20
100
5
50
Output
Resistor,
R_OUT
(k)
5
5
2
2
Full-Scale
Output
Voltage,
V_OUT (V)
Scale Typical Error at 1, 10
Factor
and 100% of Full
V_OUT/I_SENSE
Load (%)
(V/A)
1% 10% 100%
2.5
25
10 1 0.2
2.5
2.5
10 1 0.2
2
0.4
5
1 0.2
2
0.2
5
1 0.4
Rev. 1.2
7