current sensor board render

Purpose

The current sensor breakout is a breadboard compatible breakout module for the INA139 series of high-side current sensor ICs. In addition to providing a mount point for the INA139 part and the shunt resistor, the module also includes a low-impedance output suitable for driving an analog-to-digital converter.

Pinout

The potentially high-current pins - Vps and Vload - have two pins each dedicated to their functionality. It is not necessary to connect both pins.

Pin Number	Pin Label	Description
1	V_ps	Power supply pin 1 - connect to the incoming power supply
2	V_ps	Power supply pin 2 - connect to the incoming power supply
3	V_load	Load pin 1 - connect to the load
4	V_load	Load pin 2 - connect to the load
5	V_cc	Logic-level Voltage Supply
6	Gnd	Ground Pin
7	V_sns	Sense voltage pin - leave unconnected in most applications unless filtering is desired
8	V_buf	Voltage buffer output - connect this to the ADC or other measurement device

Ratings

Sustained Ratings

Each part is designed so that no more than 150mV is dropped across the part at the rated current. It is possible to run a multitude of settings on this part, but I have found that the most common combinations are targeted for 3.3V and 5V applications. Below you will find common configurations for measuring currents between 3mA to 3.0A.

Part Number	Rated Current	Transimpedance	Volts Out @ Irated
ELAS00011100	3.0A	1.65V/A	4.95V
ELAS00011101	300mA	16.5V/A	4.95V
ELAS00011102	30mA	155.1V/A	4.95V
ELAS00011103	3mA	1551V/A	4.95V
ELAS00011104	3.0A	1.1V/A	3.3V
ELAS00011105	300mA	11V/A	3.3V
ELAS00011106	30mA	103.4V/A	3.3V
ELAS00011107	3mA	1034V/A	3.3V

Common

These values are common to all part variants.

Parameter	Value
Frequency	200kHz
Accuracy	2%
Recommended Minimum V_cc	3.0V
Recommended Maximum V_cc	5.0V
Recommended Minimum V_ps	3.0V
Recommended Maximum V_ps	35.0V

Absolute Maximum Ratings

Parameter	Maximum
V_ps to GND	40.0V
V_cc	5.5V

Schematic

The schematic has three sections:

Shunt Resistor
High-Side Amplifier
Voltage Follower

The shunt resistor is the resistor through which all current flows in order to create a differential voltage.

The high-side amplifier circuit is the circuit which measures the differential voltage across the shunt resistor and amplifies the signal to a more easily measured value.

The voltage follower takes the high-impedance output of the high-side amplifier and outputs a low-impedance voltage suitable for driving a multitude of input types, such as analog-to-digital converters.

Connection Diagrams

De-coupling capacitors are not necessary as they are integrated next to the part, although extra capacitance on the inputs of the pins would not compromise the performance of the part in any way.

Common Supply

In application in which the Vps is between 3.0V and 5.0V, Vcc and Vps may be connected. This is the simplest method of connection. It is possible that this method of connection may induce noise on the V_cc pin, depending on the load noise characteristics.

Common Supply

Split Supply

In application in which the Vps is to operate above 5.0V, Vcc should be supplied with its own voltage source between 3.0V and 5.0V.

Split Supply Connection

Filtered

In some situations, it may be desireable to filter the output waveform, reducing the frequency content of the output signal while increasing the 'averaging' effect. When this is desired, a capacitor may be populated between Vsense and GND.

Split Supply with Filter