LTC6102HVCDD(RevB) 데이터 시트보기 (PDF) - Linear Technology
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LTC6102HVCDD Datasheet PDF : 20 Pages
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LTC6102/LTC6102HV
BLOCK DIAGRAM
ILOAD
L
O
A
D
VSENSE
RSENSE
RIN
–INF
VBATTERY
0.1μF
10V
V+
VREG
5V
–INS
10V
5V
5k
+IN
5k
LTC6102/LTC6102HV
–
+
V–
10V
V–
OUT
6102 BD
IOUT
VOUT
=
VSENSE
x
ROUT
RIN
ROUT
Figure 1. LTC6102/LTC6102HV Block Diagram and Typical Connection
APPLICATIONS INFORMATION
The LTC6102 high side current sense amplifier (Figure 1)
provides accurate monitoring of current through a user-
selected sense resistor. The sense voltage is amplified by
a user-selected gain and level shifted from the positive
power supply to a ground-referred output. The output
signal is analog and may be used as is or processed with
an output filter.
Theory of Operation
An internal sense amplifier loop forces –INS to have the
same potential as +IN. Connecting an external resistor,
RIN, between –INS and V+ forces a potential across RIN
that is the same as the sense voltage across RSENSE. A
corresponding current, VSENSE/RIN, will flow through RIN.
The high impedance inputs of the sense amplifier will not
conduct this input current, so it will flow through the –INF
pin and an internal MOSFET to the output pin.
The output current can be transformed into a voltage by
adding a resistor from OUT to V–. The output voltage is
then VO = V– + IOUT • ROUT.
Useful Gain Configurations
GAIN
RIN
ROUT
200
49.9Ω
10k
500
20Ω
10k
1000
10Ω
10k
4990
1Ω
4.99k
VSENSE AT VOUT = 5V
25mV
10mV
5mV
1mV
8
Selection of External Current Sense Resistor
The external sense resistor, RSENSE, has a significant effect
on the function of a current sensing system and must be
chosen with care.
First, the power dissipation in the resistor should be
considered. The system load current will cause both heat
dissipation and voltage loss in RSENSE. As a result, the sense
resistor should be as small as possible while still providing
the input dynamic range required by the measurement.
Note that input dynamic range is the difference between
the maximum input signal and the minimum accurately
reproduced signal, and is limited primarily by input DC
offset of the internal amplifier of the LTC6102. In addition,
RSENSE must be small enough that VSENSE does not exceed
the maximum sense voltage specified by the LTC6102 or
the sense resistor, even under peak load conditions. As
an example, an application may require that the maximum
sense voltage be 100mV. If this application is expected
to draw 20A at peak load, RSENSE should be no more
than 5mΩ.
Once the maximum RSENSE value is determined, the
minimum sense resistor value will be set by the resolu-
tion or dynamic range required. The minimum signal
that can be accurately represented by this sense amp is
limited by the input offset. As an example, the LTC6102
has a typical input offset of 3μV. If the minimum current
is 1mA, a sense resistor of 3mΩ will set VSENSE to 3μV.
6102fb
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