Si8540
H
I G H
- S
ID E
C
URRENT
S
ENSE
A
MPLIFIER
Features
Complete, unidirectional high-side
current sense capability
0.2% full-scale accuracy
+5 to +36 V supply operation
85 dB power supply rejection
90 µA max supply current
9 µA shutdown current
Operating Temperature Range:
–40 to +85 °C
5-pin SOT-23 package
RoHS-compliant
Applications
Battery chargers
Smart battery packs
DC motor control
Backup systems
Current control applications
5-Pin SOT-23
Ordering Information:
See page 12.
Pin Assignments
Description
The Si8540 is a unidirectional, 36 V (max), high-side current sense
amplifier for use in applications requiring current monitoring and/or
control. This device draws bias current from the high-side line to which it
is attached, eliminating the need for an external supply. It measures
current from 0.1 to 10 A by sensing the voltage across an external sense
resistor (or PCB trace) from dc to 20 kHz and can achieve measurement
accuracies of 0.2% (typical) at full load. The device output is a current
signal proportional to measured current and is easily converted to a
scaled voltage using a single external resistor. The Si8540 is available in
compact SOT-23 package.
RG1
GND
SHDN
1
2
3
SOT-23
5
RG2
4
OUT
Functional Block Diagram
V
SOURCE
R
SENSE
I
LOAD
Patents pending
R
G1
R
G2
LOAD
Si8540
V
OUT
R
OUT
Rev. 1.2 8/13
Copyright © 2013 by Silicon Laboratories
Si8540
Si8540
T
ABLE O F
C
ONTENTS
Section
Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2. Typical Application Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3.1. Application Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
4. Typical Performance Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
5. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Device Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Package Outline: SOT-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. Land Pattern: SOT-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Rev. 1.2
3
Si8540
1. Electrical Specifications
Table 1. Absolute Maximum Ratings
Parameter
Voltage at RG1, RG2, SHDN to GND
Differential Input Voltage, RG1 to RG2
Voltage at OUT
Current into SHDN, GND, OUT, RG1, RG2
Continuous Power Dissipation (T
A
= +70 °C)
5-pin SOT23 derate 7.1 mW/°C above +70 °C*
Operating Temperature Range
Junction Temperature, T
JMAX
Value
–0.3 to +40
±0.3
–0.3 to +8
±50
571
–40 to +85
Up to +150
Unit
V
V
V
mA
mW
°C
°C
*Note:
The device is mounted on a standard PCB with a 100 mm
2
copper foil connected to the GND pin, no airflow.
Permanent device damage may occur if the absolute maximum ratings are exceeded, and prolonged use at the
absolute maximum ratings may affect reliability. It is recommended that the device operate within the limits indicated in
Table 2, “DC and AC Characteristics".
4
Rev. 1.2
Si8540
Table 2. DC and AC Characteristics
Parameter
Operating Voltage
Operating Frequency
Total Input Current
Input Currents
Input Current Matching
Sense Voltage
1
OUT Current Accuracy
No-Load OUT Error
Low-Level OUT Error
Power-Supply Rejection
Shutdown Supply Current
SHDN Input Low Voltage
SHDN Input Low Current
SHDN Input High Voltage
SHDN Input High Current
OUT Output Voltage Range
OUT Output Resistance
(Internal)
OUT Rise, Fall Time
PSR
I
RG1
+I
RG2
V
IL
I
IL
V
IH
I
IH
V
OUT
V
SHDN
= 2.4 V
V
OUT
clamped at 8 V
I
OUT
= 1.5 mA
V
SENSE
= 5 mV to 150 mV,
R
OUT
= 2 = k,
C
OUT
= 50 pF, 10% to 90%
(Note 2)
V
SENSE
= 5 to 150 mV,
R
OUT
= 2 k,
C
OUT
= 50 pF (Note 2)
I
OUT
For I
OUT
> 1.5 mA the internal
current limitation starts to limit the
output current
V
SHDN
= 0 V
(Unless otherwise specified: V
RG1
=+5 to +36 V, RG1 =RG2 =200, V
SENSE
=0 V, T
A
= –40 to +85 °C)
Symbol
V
RG1
F
I
RG1
+I
RG2
I
RG1
, I
RG2
I
OS
V
SENSE
I
RG
/I
OUT
Test Condition
Min
5
0
Typ
—
20
46
23
±0.4
100
±0.2
0.5
±0.5
-85
3.5
—
—
—
—
—
3
0.4
0.5
Max
36
—
90
45
±1.5
—
±1.5
15
+10
—
9
0.3
1.0
—
1.0
V
RG1
– 3.5
(<8)
—
—
—
Unit
V
kHz
µA
µA
µA
mV
%
µA
µA
dB
µA
V
µA
V
µA
V
M
µs
µs
I
LOAD
= 0 A
I
LOAD
= 0 A
I
RG1
– I
RG2
V
SENSE
= 100 mV
V
RG1
=10 V, V
SENSE
=0 V
V
RG1
=10 V, V
SENSE
=3 mV
V
SENSE
= 100 mV
V
SHDN
= 2.4 V
—
—
—
—
—
—
—
—
—
—
—
2.4
—
0
1
—
—
OUT Settling Time to 1% of
Final Value
Maximum Output Current
—
—
1.5
1
2
—
—
—
10
µs
µs
mA
Notes:
1.
V
SENSE
is the voltage across the sense resistor.
2.
C
OUT
is the load capacitance seen by the OUT pin.
Rev. 1.2
5
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