High-side current sensing with comparator circuit



This high-side, current sensing solution uses one comparator with a rail-to-rail input common mode range to create an over-current alert (OC-Alert) signal at the comparator output (COMP OUT) if the load current rises above 1 A. The OC-Alert signal in this implementation is active low. So when the 1-A threshold is exceeded, the comparator output goes low. Hysteresis is implemented such that OC-Alert will return to a logic high state when the load current reduces to 0.5 A (a 50% reduction). This circuit utlizes an open-drain output comparator in order to level shift the output high logic level for controlling a digital logic input pin. For applications needing to drive the gate of a MOSFET switch, a comparator with a push-pull output is preferred.
  • Load current:
    • Over current, Ioc = 1 A
    • Recovery current, Irc = 0.5 A
  • System supply typical Vs = 10 V
  • Comparator output status:
    • Over current: Vol < 0.4 V
    • Normal operation: Voh = Vpu = 3.3 V
TLV1701-Q1 Automotive single high-voltage, low power comparator TLV3701-Q1 Automotive Single Nanopower Push-Pull Comparator TLV7021 Low power, small size comparator with open-drain output
General-purpose op amps
LM2902B Quad 36-V 1.2-MHz operational amplifier with -40°C to 125°C operation LM2902B-Q1 Automotive quad, 36-V, 1.2-MHz operational amplifier with -40°C to 125°C operation LM2904BA-Q1 Automotive, dual, 36-V, 1.2-MHz, 2-mV offset voltage operational amplifier LM324B Quad, 36-V 1.2-MHz 3-mV offset voltage operational amplifier with -40°C to 85°C operation OPA4991-EP Enhanced-product, quad, 40-V 4.5-MHz rail-to-rail input and output (RRIO) operational amplifier

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Type Title Date
* Circuit design High-side current sensing with comparator circuit Sep. 20, 2018

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