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