CIRCUIT060075

High-speed overcurrent detection circuit

CIRCUIT060075

Overview

This high-speed, low-side overcurrent detection solution is implemented with a single zero-drift fast-settling amplifier (OPA388) and one high-speed comparator (TLV3201). This circuit is designed for applications that monitor fast current signals and overcurrent events, such as current detection in motors and power supply units.

The OPA388 is selected for its widest bandwidth with ultra-low offset and fast slew rate. The TLV3201 is selected for its fast response due to its small propagation delay of 40 ns and rise time of 4.8 ns. This allows the comparator to quickly respond and alert the system of an overcurrent event all within the transient response time requirement. The push-pull output stage also allows the comparator to directly interface with the logic levels of the microcontroller. The TLV3201 also has low power consumption with a quiescent current of 40 µA.

Typically for low-side current detection, the amplifier across the sense resistor can be used in a noninverting configuration. The application circuit shown, however, uses the OPA388 as a differential amplifier across the sense resistor. This provides a true differential measurement across the shunt resistor and can be beneficial in cases where the supply ground and load ground are not necessarily the same.
Features
  • Overcurrent levels: I_IN = 0 A to 1.0 A
  • Supply:
    • V+ = 5 V
    • V- = 0 V
  • Transient response time: t = <10 µs
Comparators
TLV3201 5.5-V, high-speed, single push-pull comparator TLV7021 Low power, small size comparator with open-drain output
Precision op amps (Vos<1mV)
OPA388 Single, 10-MHz, CMOS, zero-drift, zero-crossover, true RRIO precision operational amplifier

Technical documentation

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Type Title Date
* Application note High-speed overcurrent detection circuit (Rev. A) Jan. 17, 2019
* Application note Advantages of using Nanopower Zero Drift Amp for Mobile Phone Battery Voltage Mo (Rev. A) Dec. 21, 2017
* Application note Current Sensing in No-Neutral Light Switches (Rev. A) Oct. 16, 2017
Application note GPIO Pins Power Signal Chain in Personal Electronics Running on Li-Ion Batteries Feb. 12, 2018

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