Datasheet
B
LMV641
LMV641
STANDOFF DISTANCE
U1
U2
20 k:
BRIDGE TEMPCO COMPENSATION NETWORK
V
+
-
+
G = 23.2
BW
-3 dB
= 431 kHz
580:
1%
24.5 k:
1%
24.5 k:
1%
568 k:
1%
HONEYWELL
HMC1051Z
or EQUIVALENT
CONDUCTOR TO BE
CURRENT MEASURED
I
(AC or DC)
FROM mAs TO 20A
V
+
20 k:
5 k:
0.1 PF
9V
ALKALINE
BATTERY
V
+
V
OUT
V
+
R
TH
R
A
R
B
-
+
TO ADC or
METER
CIRCUITRY
OFFSET TRIM
LMV641
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SNOSAW3C –SEPTEMBER 2007–REVISED FEBRUARY 2013
Compensation by External Resistor
In some applications it is essential to drive a capacitive load without sacrificing bandwidth. In such a case, in the
loop compensation is not viable. A simpler scheme for compensation is shown in Figure 42. A resistor, R
ISO
, is
placed in series between the load capacitance and the output. This introduces a zero in the circuit transfer
function, which counteracts the effect of the pole formed by the load capacitance, and ensures stability. The
value of R
ISO
to be used should be decided depending on the size of C
L
and the level of performance desired.
Values ranging from 5Ω to 50Ω are usually sufficient to ensure stability. A larger value of R
ISO
will result in a
system with less ringing and overshoot, but will also limit the output swing and the short circuit current of the
circuit.
Figure 42. Compensation by Isolation Resistor
TYPICAL APPLICATIONS
ANISOTROPIC MAGNETORESISTIVE SENSOR
The low operating current of the LMV641 makes it a good choice for battery operated applications. Figure 43
shows two LMV641s in a portable application with a magnetic field sensor. The LMV641s condition the output
from an anisotropic magnetoresistive (AMR) sensor. The sensor is arranged in the form of a Wheatstone bridge.
This type of sensor can be used to accurately measure the current (either DC or AC) flowing in a wire by
measuring the magnetic flux density, B, emanating from the wire.
Figure 43. A Battery Operated System for Contact-Less Current Sensing Using an Anisotropic
Magnetoresistive Sensor
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