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ADM1191 returns wrong values of voltage and current

Question asked by libr on Oct 12, 2012
Latest reply on May 20, 2013 by Ren


I use ADM1191 as a power meter (voltage and current) for motor control application. I init IC to continious convert both voltage and current, or voltage only, or current only. MCU reads values by I2C but returned voltage is less than measured at IC input by ~1.8 V (try from 12 V to 24 V) and current MSB (all 8 high bits) are zeros. It doesn't matter what way I get data - 3 bytes of both voltage and current or 2 bytes separate voltage and current. VRANGE is 0 (26.52 V), ALERT and SETV pins disconnected from MCU. Test on current about 260 mA with ~3 A max (Rsense = 0.033 Ohm), current code should be about 300.

What could be wrong? Could it be firmware or schematic mistake?