Dual-Channel, 0V to 76V Current-Sense Amplifier

This is a dual-channel current sense amplifier that utilizes the MAX40201F, a high-precision, high-voltage current-sense amplifier. This circuit measures the current flowing through a shunt resistors and provides a voltage output proportional to that current.

The MAX40201F is available in various gain configurations; this project employs the MAX40201F with a gain (G) of 50V/V. With a 0.05 Ohm shunt resistor, the output is 2.5V for a 1A current flow (1A/2.5V). Higher current measurements can be achieved by using a lower-value shunt resistor or by selecting a MAX40201 chip with a lower gain. The input common-mode range is 0V to 76V.

Current Sense Resistor vs. Gain Considerations:

Ideally, the maximum load current should generate the full-scale sense voltage across the current-sense resistor. The appropriate gain should be selected to achieve the desired maximum output voltage for the specific application. The relationship is defined by the following equation:

Vout = I-Load * Rsense * Gain

For example, with a 1A load current, a 0.05 Ohm shunt resistor, and a gain of 50V/V, the output voltage is:

Vout = 1A * 0.05 Ohm * 50V/V = 2.5V

Where Rsense is the full-scale sense voltage (50mV for a gain of 50V/V). This formula allows the user to select the appropriate sense resistor value based on the specific application requirements.

Features

• Power Supply 5V DC (Range 2.7V to 5.5V)
• Current Monitor Output 2.5V/1Amp
• Load Current Monitor Up to 2Amp
• Common Mode Input Voltage Range 0 to 76V
• 2 Channel Current Sense
• Precision Output, Gain Error less than 0.1%
• Low 12μV (max) Input Offset Voltage
• Screw Terminal Connectors for Inputs and Load Outputs
• Header Connector for Power Supply and Current Monitor Outputs (VO)
• 4X4MM PCB Mounting Holes
• PCB Dimensions 41.28 x 34.13 mm

The MAX40201 dual-channel, high-side, current-sense amplifier has VOS of less than 12µV (max) and gain error of less than 0.1% (max). The outputs of the MAX40201 are voltage outputs capable of swinging to a few tens of millivolts of the VDD rail and ground. The MAX40201 features an input common-mode voltage range from 0V to 76V with 80kHz of small-signal bandwidth, which makes it ideal for interfacing with a SAR ADC for multichannel multiplexed data acquisition systems.

Measuring the Load Current

The load current is measured as a voltage drop (VSENSE) across an external sense resistor. This voltage is then amplified by the current-sense amplifier and presented at its VOUT_ pin. Like all differential amplifiers, the output voltage has two components of error (an offset error and a gain error). The offset error affects accuracy at low currents and a gain error affects accuracy at large currents. Both errors affect accuracy at intermediate currents. By minimizing both offset and gain errors, accuracy can be optimized over a wide dynamic range.

Connections

• CN1: Pin 1 = +Input 1, Pin 2 = GND
• CN2: Pin 1 = +Output 1 (Load), Pin 2 = GND
• CN3: Pin 1 = VDD/5V DC, Pin 2 = Voltage Output 1, Pin 3 = Voltage Output 2, Pin 3 = GND
• CN4: Pin 1 = +Input 2, Pin 2 = GND
• CN5: Pin 1 = +Output 2 (Load), Pin 2 = GND
• D1: Power LED

Schematic

Parts List

Connections

Application Diagram

Gerber View

Photos

MAX40201 Datasheet