Bidirectional Current Sense Amplifier with PWM-Rejection

Enabling Dramatic Size and Performance Improvement for In-Phase Measurement in DC Servo Drives

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The MAX40056 is a bidirectional current-sense amplifier with an input common-mode range that extends from -0.1V to +65V together with protection against negative inductive kickback voltages to -5V. This CSA is well-suited for phase current monitoring of inductive loads, such as motors and solenoids, where pulse width modulation is used to control the drive voltage and current. The MAX40056 uses an improved technique to help reject common-mode input PWM edges with slew rates up to and beyond ±500V/µs. Common mode rejection ratio (CMRR) is typically 60dB (50V, ±500V/µs input) and 140dB DC, typical.

The MAX40056 has an internal +1.5V reference for use with a nominal +3.3V power supply. The reference can also be used to drive an adjoining differential ADC. The reference is used to offset the output to indicate the direction of the input sensed current. The REF pin can source current into external loads and helps to avoid the performance compromises resulting from routing reference voltages across noisy PCBs. Alternatively, for higher supply voltages and higher full-scale output swings, the internal reference can be overridden by a higher voltage, external reference.

The internal or external reference can be used to define the trip threshold for the integrated overcurrent comparator. This can provide immediate indication of an overcurrent fault condition.

The MAX40056 operates over the full -40°C to +125°C temperature range and runs from a supply voltage of +2.7V to +5.5V. It is offered in a 2.02mm x 1.4mm 8-pin wafer-level package (WLP) and 8-pin µMAX packages.

Design Solution: How Less Can Be More in Motor Control Design ›

MAX40056F, MAX40056T, MAX40056U: Simplified Block Diagram MAX40056F, MAX40056T, MAX40056U: Simplified Block Diagram Enlarge+

Key Features

  • Fast, 500ns PWM Edge recovery from 500V/µs PWM Edges
  • 60dB AC CMRR Rejection at 50V, ±500V/µs PWM Edges
  • 140dB DC CMRR Rejection
  • -0.1V to +65V Input Voltage Range
  • -5V to +70V Protective Immunity
  • 300kHz, -3dB Bandwidth
  • Multiple Gain Options; 10V/V, 20V/V, 50V/V
  • Internal, 1% Reference for Bidirectional Offset
  • 5µV (Typ) Input Offset Voltage
  • Rail-to-Rail Output
  • 2.02mm x 1.4mm WLP-8 and 8-pin μMAX
  • -40°C to +125°C Temperature Range


  • Automotive
  • Battery Stack Monitors
  • Current Monitoring of Inductive Loads
  • PWM H-Bridge Motor In-line/In-phase/Winding Current Sensing
  • Solenoid Current Sensing

See parametric specs for Current Sense Amplifiers (52)

Part NumberOutput FormatCMVR
Bi-Dir. Curr. SenseVSENSE_FS
VOS @25°C
GainGain Accuracy @25°C
ComparatorsReferenceOper. Temp.
minmaxminmaxtyprecomm.maxmax@ -3dBSee Notes
MAX40056F Voltage-0.1652.75.56000Yes+/-502050 V/V1.53002
-40 to +125
$1.25 @1k
MAX40056T +/-12520 V/V
$1.19 @1k
MAX40056U +/-25010 V/V
$1.19 @1k

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX40056EVKIT: Evaluation Kit for the MAX40056F, MAX40056T, MAX40056U

Tools & Models

  • MAX40056F Orcad Library
  • Request Reliability Report for: MAX40056F 
    Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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