DEMO CIRCUIT 1 3 6 3 Q UICK S TA RT LT6107 G UIDE L T6 1 0 7 H ig h Te m p e ra tu re H ig h S id e Cu rre n t S e n s e in a S OT-2 3 DESCRIPTION Demonstration circuit 1363 is a General Purpose HighSide Current-Sense Amplifier featuring the LT6107. This demo board amplifies an on-board current-sense resistor voltage-drop, providing a precision uni-polar output voltage proportional to load current. The demo circuit includes scaling resistors that program the gain of the circuit to 50V/V. The LT6107 is pow ered from the same supply that the sense resistor is connected to and provides a ground referenced output. The LT6107 can perform current measurements on supplies ranging from 2.7V to 36V. Since the output voltage is developed as a controlled current through a load resistance, groundloop errors can be eliminated by simply locating the load resistor at the destination point (subsequent signal PERF ORM ANCE SU M M ARY SYM BOL VIN VM ON IM ON IOUT IINQ tR PARAM ETER M onitored Supply Input Range M easurement Output Signal M easurement Output Signal(current mode) Output Load Current Range VIN Quiescent Current VM ON step-response time processing such as A/D conversion).Remote loading can be evaluated by simply removing the on board load resistor (R3). DC1363 is fabricated from FR-406 high-temp epoxyglass so that the full 150 operation of the LT6107 can be demonstrated. Other key performance characteristics of the LT6107 and DC1363 are show n in the Performance Summary below . Design files for this circuit board are available. Call the LTC factory. L, LT are registered trademarks ofLinear Technology Corporation.Other product names may be trademarks ofthe companies that manufacture the products. Specifications are at TA = 25C CONDITIONS M IN 2.7 IOUT = 5A IOUT = 5A, R3 removed Thermallimit ofRSENSE VIN =12V, IOUT = 0A IOUT step from 0A to 5A TYP 3... 28 2.5 500 M AX 36 5 65 5 UNITS V V A A A s OPERATING PRINCIPL ES The LT6107 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 V- (ground in this demo circuit). The circuit gain is established by the ratio of the output resistor to the input resistor and is essentially as accurate as the resistors used. In DC1363 as shipped, the sense resistor installed is 10m and the resistor ratio sets the gain to 50V/V, so the nominaloutput scaling is 500mV per Ampere of load current. Other scalings can be produced by resistor replacement on the demo circuit. The DC1363 Schematic diagram is show n in Figure 2. 1 LT6107 Q U ICK START PROCEDU RE Demonstration circuit 1363 is easy to set up to evaluate the performance of the LT6107. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below : 1. W ith pow er off, connect the pow er supply positive to IN and the common to GND. This supply should be in the range of2.7V to 36V.Ifthis 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 2. Connect a voltmeter or oscilloscope probe to the M ON terminal, w ith the common connection or ground clip tied to GND. 3. Connect a load to the O UT terminal (positive) and return (negative) to the common of the pow er supply. The load may be a pow er resistor, active load instrument, or other circuit ofinterest. 4. Turn on the pow er supply. 5. M easure an output voltage that corresponds to the load current. VM ON = 0.5xIOUT for the factory installed resistors. DMM DMM A COM V A COM V LOAD (10) Figure 1. Proper M easurem ent Equipm ent Setup 2 LT6107 Figure 2. DC1363 Schem atic Diagram 3