SBAA347 June 2022 AMC1300 , AMC1300B-Q1 , AMC1301 , AMC1301-Q1 , AMC1400 , AMC3301 , AMC3301-Q1 , TLV6002 , TLV9002
Current Source |
Input Voltage |
Output Voltage | Single Power Supply | ||
---|---|---|---|---|---|
IIN MIN | IIN MAX | VIN DIFF, MIN | VIN DIFF, MAX |
VOUT SE |
VDD |
–10 A | 10 A | –250 mV | 250 mV |
55 mV to 3.245 V |
3.3 V |
This isolated current sensing circuit can accurately measure load currents from, but not limited to, –10 A to 10 A with a nominal power dissipation of 2.5 W across a 25-mΩ shunt resistor. The linear range of the isolated amplifier input is from –250 mV to 250 mV with a differential output swing of –2.05 V to 2.05 V and an output common-mode voltage (VCM) of 1.44 V. The gain of the isolated amplifier circuit is fixed at 8.2 V/V. A TLV9002 is used to transform the differential output signal to a single-ended signal that can be used with a single-ended ADC such as the ADS8326 as well as buffer the VCM derived from a voltage divider. A 1.65-V reference voltage is used to set the final output voltage range and the common-mode voltage level.
In order to stay within the output limitations of the TLV9002, the output of the AMC3301 needs to be attenuated by a factor of 3.19/4.1. When R3 = R4 and R5 = R6, the following transfer function for the differential to single-ended stage can be used to calculate R5 and R6.
Using standard 0.1% resistor values, a 7.77 kΩ can be used. This will provide a maximum output swing within the limitations of the TLV9002.
When the C1 = C2 = 1 nF and R5 = R6 = 7780 Ω, the cutoff frequency can be calculated to be 20.45 kHz.