DC1114A - Demo Manual

DEMO CIRCUIT 1 1 1 4
Q UICK S TA RTLT6100
G UIDE
DESCRIPTION
L T6 1 0 0
P re c is io n , G a in S e le c ta b le H ig h
S id e Cu rre n t S e n s e A m p lifie r
Demonstration Circuit 1114 is an Precision, Gain
Selectable High Side Current Sense Amplifier featuring
the LT6100.
especially suitable for measuring battery system current
since the monitoring-input current draw s become
negligible w hen VCC is pow ered dow n.
This demo board amplifies a current-sense resistor
voltage-drop, providing a precision uni-polar output
voltage proportional to load current. The demo circuit is
equipped w ith jumpers to facilitate setting the pinstrapped gain configuration.The LT6100 is unique in that
it is pow ered from a low voltage (dow n to 2.7V) w hile it
measures current of an Over-The-Top® higher voltage
pow er bus (1.4V or more above VCC). This device is
The key performance characteristics of the LT6100 and
DC1114 are show n in the Performance Summary below .
PERF ORM ANCE SU M M ARY
SYM BOL
VIN
PARAM ETER
M onitored Supply Input Range
VCC
VM ON
IOUT
ICC
IINQ
IINSD
tR
Amplifier Supply Range
M easurement Output Signal
Output Current Range
VCC Supply Current
VIN Quiescent Current
VIN Current during Shutdow n
VM ON step-response time
Design files for this circuit board are available. Call the
LTC factory.
L, LT, Over-The-Top are registered trademarks ofLinear Technology Corporation.Other
product names may be trademarks ofthe companies that manufacture the products.
Specifications are at TA = 25°C
CONDITIONS
M IN
VCC
+1.4V
2.7
IOUT = 5A, Jumper settings:A4=VEE, A2=OUT
Thermallimit ofRSENSE
VIN = VCC +1.4V, IOUT = 0A
VIN = VCC +1.4V, IOUT = 0A
VCC = 0V, IOUT = 0A, VIN ≤ 48V
IOUT step from 0A to 5A
TYP
5… 24
M AX
48
3… 5
2.5
36
60
10
1
50
UNITS
V
V
V
A
µA
µA
nA
µs
7
130
OPERATING PRINCIPL ES
The LT6100 operates by amplifying the voltage drop on a
sense resistor placed in series w ith the pow er source ofa
load to be monitored. The sense inputs of the amplifier
differentially measure the sense-resistor drop to control
an internalvariable current source that allow s translation
of the input information to a level referenced to VEE
(ground in this demo circuit). An internal post-amplifier
provides additional gain and buffers the output signal.
The post-amplifier gain is established by the pin strap
configuration of the part. In DC1114 as shipped, the
sense resistor installed is 20mΩ and the pin strapping
jumpers set the gain to 25V/V, so the nominal output
scaling is 500mV per ampere of load current. Other
scalings can be produced by simple jumper position
changes on the demo circuit.
The DC1114 Schematic diagram is show n in Figure 2.
1
LT6100
Q U ICK START PROCEDU RE
Demonstration circuit 1114 is easy to set up to evaluate
the performance of the LT6100. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below :
1. Place jumpers in the follow ing positions:
A4 to the VEE position
A2 to the OUT position
2. W ith pow er off, connect the load driving pow er supply
positive to IN and the common to GND. This supply
should be in the range of 4.1V to 48V.If this supply is
not equipped w ith an accurate current readout, a
DM M (set to measure Amperes) may be connected in
series w ith the supply as show n in Figure 1.
NOTE. Be sure that the current capacity ofthe DM M is adequate to
handle the intended load current.
POWER
SUPPLY
+ COM
POWER
SUPPLY
3. W ith pow er off, connect the amplifier supply positive
to VCC and the common to GND. This supply should
be in the range of2.7V to VIN -1.4V.
4. Connect a voltmeter or oscilloscope probe to the M ON
terminal, w ith the common connection or ground clip
tied to GND.
5. Connect a load to the O UT terminal (positive) and
return (negative) to the common of the load driving
pow er supply. The load may be a pow er resistor,
active load instrument, or other circuit ofinterest.
6. Turn on the pow er supplies.
7. Check for an output voltage that corresponds to the
load current. VM ON = 0.5×IOUT for the jumper settings
indicated in step 1.
NOTE. At times w hen the load supply voltage is near or below the
amplifier supply voltage, the M ON output w illbecome unpredictable
(may assume a value anyw here betw een 0V and VCC).
+ COM
DMM
DMM
A COM V
A COM V
LOAD
(10Ω)
Figure 1. Proper M easurem ent Equipm ent Setup
2
LT6100
Figure 2. DC1114 Schem atic Diagram
3
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