DC1192A - Demo Manual

DEMO CIRCUIT 1 1 9 2
Q UICK S TA RT LT6105
G UIDE
DESCRIPTION
L T6 1 0 5
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 1192 is a Precision, Gain Selectable High Side Current Sense Amplifier featuring the
LT6105.
suitable for measuring supply bus loading as they are
brought up. W hen provided w ith a negative supply, it is
capable ofmonitoring negative supplies.
This demo board amplifies a current-sense resistor IRdrop, providing a precision uni-polar output voltage proportional to load current. The LT6105 is pow ered from a
supply voltage (from 2.85V up to 36V) w hile it measures
current ofa voltage pow er bus (0V to 44V). This device is
suitable for measuring battery system current since the
monitoring-input current draw s become negligible w hen
VCC is pow ered dow n. Its 0V and up input range makes it
The key performance characteristics of the LT6105 and
DC1192 are show n in the Performance Summary below .
PERF ORM ANCE SU M M ARY
SYM BOL
VIN
VCC
AV
AZ
VOUT
IM AX
ICC
IBIAS
IINPD
tR
PARAM ETER
M onitored Supply Input Range
Amplifier Supply Range
Voltage Gain
TotalCurrent to Voltage Gain
Output Voltage Range
M aximum Sense Current
V+ (=Vcc) Supply Current
VS+ Bias Current
VS+ Current during Pow er Dow 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
-0.3
2.85
RIN1 = RIN2 = 100, ROUT = 4.99k
RSENSE = .020 Ohm
V+ = 3V
Thermallimit ofRSENSE (2W atts)
V+= 36V, VS+=3V, VSENSE=0V
VS+ = 3V, VSENSE=0V
V+= 0V, VS+ =44V, VSENSE=0V
IOUT step from 0A to 5A
TYP
0… 44
3… 28
50
1
2
150
15
.001
50
M AX
44
36
10
250
25
1
UNITS
V
V
V/V
V/A
V
A
µA
µA
µA
µs
OPERATING PRINCIPL ES
The LT6105 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 DC1192 as shipped, the
sense resistor installed is 20mΩ and the resistors set the
gain to 50V/V, so the nominal output scaling is 1V per
Ampere of load current. Other scalings can be produced
by changing the resistors.
The DC1192 Schematic diagram is show n in Figure 2.
1
LT6105
Q U ICK START PROCEDU RE
Demonstration circuit 1192 is easy to set up to evaluate
the performance of the LT6105. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below :
1. W ith pow er off, connect the load driving pow er supply
positive to SOURCE and the common to GND. This
supply should be in the range of 0V to 44V. 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.
3. Connect a voltmeter or oscilloscope probe to the Vout
terminal, w ith the common connection or ground clip
tied to GND.
4. Connect a load to the TO LOAD 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.
5. Turn on the pow er supplies.
6. Check for an output voltage that corresponds to the
load current: VM ON = 1.0×IO UT.
2. W ith pow er off, connect the amplifier supply positive
to VCC and the common to GND. This supply should
be in the range of2.85V to 36V.
POWER
SUPPLY
3.0
+ COM
POWER
SUPPLY
10.
+0
COM
1.00
0
DMM
1.00
0
DMM
A COM V
A COM V
LOAD
(10Ω)
Figure 1. Proper M easurem ent Equipm ent Setup
2
LT6105
3
Similar pages