DEMO CIRCUIT DC1536 LTC6102-1 QUICK START GUIDE LTC6102-1 Precision Zero Drift Current Sense Amplifier DESCRIPTION Demonstration circuit 1536 is a General Purpose HighSide Current-Sense Amplifier featuring the LTC6102-1. This demo board amplifies an on-board current-sense resistor voltage-drop, providing a precision uni-polar output voltage proportional to load current through the sense resistor. The demo circuit includes scaling resistors that program the gain of the circuit to 33.3V/V. The LTC6102-1 is powered from the same supply that the sense resistor is connected to and provides a ground referenced output. The LTC6102-1 can perform current measurements on supplies ranging from 4V to 60V. Since the output voltage is a function of a controlled current through Rout, ground-loop errors can be eliminated by simply locating Rout at the destination point (subsequent signal process- ing such as A/D conversion). Remote positioning of Rout can be evaluated by simply removing the on board Rout resistor (R3). The key performance characteristics of the LTC6102-1 and DC1536 are shown in the Performance Summary below. The LTC6102-1 is the same as the LTC6102 but has an Enable feature at pin 3. On the Demo Board this pin is pulled up by a 1MΩ resistor so the default setting is the LTC6102-1 is Enabled. Design files for this circuit board are available. Call the LTC factory. L, LT are registered trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. PERFORMANCE SUMMARY Specifications are at TA = 25°C SYMBOL VIN VMON IMON IOUT IINQ tR PARAMETER Monitored Supply Input Range Measurement Output Signal Measurement Output Signal (current mode) Output Load Current Range VIN Quiescent Current VMON step-response time CONDITIONS MIN 4 IOUT = 10A IOUT =10A, R3 removed Thermal limit of RSENSE VIN =12V, IOUT = 0A IOUT step from 0A to 10A TYP 5…48 2.0 400 MAX 60 12 230 4 UNITS V V µA A µA µs OPERATING PRINCIPLES The LTC6102-1 operates by amplifying the voltage drop across a sense resistor placed in series with the power source of the load to be monitored. The sense inputs of the amplifier differentially measure the sense-resistor drop to control an internal variable current source that allows 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 DC1536 as shipped, the sense resistor installed is 6mΩ and the resistor ratio sets the gain to 33.3V/V, so the nominal output scaling is 200mV per Ampere of load current. Other scaling can be produced by resistor replacement on the demo circuit. The DC1536 Schematic diagram is shown in Figure 2. 1 LTC6102-1 QUICK START PROCEDURE Demonstration circuit 1536 is easy to set up to evaluate the performance of the LTC6102-1. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1. With power off, connect the power supply positive to IN and the common to GND. This supply should be in the range of 4V to 60V. If this supply is not equipped with an accurate current readout, a DMM (set to measure Amperes) may be connected in series with the supply as shown in Figure 1. NOTE. Be sure that the current capacity of the DMM is adequate to handle the intended load current. The Load Resistor must have the appropriate power rating. POWER SUPPLY 10. + COM 2. Connect a voltmeter or oscilloscope probe to the MON terminal, with the common connection or ground clip tied to GND. 3. Connect a load to the OUT terminal (positive) and return (negative) to the common of the power supply. The load may be a power resistor, active load instrument, or other circuit of interest. 4. Turn on the power supply. 5. Measure an output voltage that corresponds to the load current. VMON = 0.2×IOUT for the factory installed resistors. 1.0 0.2 DMM DMM A COM V A COM V LOAD (10Ω) Figure 1. Proper Measurement Equipment Setup 2 LTC6102-1 Figure 2. DC1536 Schematic Diagram 3