INA139NA/3KG4

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1. Describe

The INA139NA/3KG4 and INA169 are high-side, unipolar, shunt monitors. Wide input common mode voltage range, high speed, low quiescent current and tiny SOT-23 package make it suitable for a variety of applications. The input common-mode voltage and supply voltage are independent, ranging from 2.7 V to 40 V for the INA139 and 2.7 V to 60 V for the INA169. Quiescent current is only 60 µA, allowing power supplies to be connected to either side of the current measurement shunt with minimal error. The device converts a differential input voltage to a current output. This current is converted back to voltage by an external load resistor that can be set to any gain from 1 to over 100. Although the circuit is designed for current shunt measurements, the circuit has creative applications for measurement and level shifting. Both the INA139 and INA169 are available in a 5-pin SOT-23 package. The INA139 device is specified from –40°C to +125°C, while the INA169 is specified from –40°C to +85°C.

2. Feature

    1. Complete unipolar high side current measurement circuit

    2. Wide supply and common mode ranges

    3. INA139: 2.7 V to 40 V

    4. INA169: 2.7 V to 60 V

    5. Separate power supply and input common mode voltage

    6. Single Resistor Gain Setting

    7. Low Quiescent Current: 60 µA (typ)

    8. 5-Pin, SOT-23 Package

3. Application

    1. Current Shunt Measurements:

        – car, phone, computer

    2. Portable and battery backup system

    3. charger

    4. Energy management

    5. cell phone

    6. Precision current source

4. Detailed description

The INA139NA/3KG4 and INA169 devices consist of high voltage, precision op amps, precision low profile Thin film resistors are trimmed in production for absolute tolerance and low noise output transistors. INA139 and INA169 devices can be powered from a single supply where the input voltage exceeds the power Voltage. The INA139 and INA169 devices are ideal for measuring small differential voltages such as The voltage developed through a shunt resistor in the presence of large common-mode voltages.

5. Pin configuration

6. Pin Description

7. Function Description

    1. Output voltage range

        The output of the INA139NA/3KG4 is a current, which is converted to a voltage by a load resistor (RL). The output current remains accurate within the compatible voltage range of the output circuit. The shunt voltage as well as the input common mode and supply voltages limit the maximum possible output swing. The maximum output voltage compliance is limited by the lower of Equation 1 and Equation 2.

    2. Bandwidth

        The measurement bandwidth is affected by the load resistance (RL) value. The high gain due to high RL values results in a narrower measurement bandwidth. To obtain the widest possible bandwidth, keep capacitive loading on the output to a minimum. A typical characteristic graph shows the reduction in bandwidth due to capacitive loading. If bandwidth limiting (filtering) is required, a capacitor can be added to the output. This will not cause instability.

8. Application Information

The load current IS is drawn from the power supply VS through the shunt resistor RS. An internal op amp forces a voltage drop across shunt resistor VS through RG1, causing current to flow into the collector of Q1. An external resistor RL converts the output to current to the voltage VOUT on the OUT pin. The maximum differential input voltage is accurately measured at 0.5 V and the output current is 500 µA. Differential input voltages up to 2 V will not cause damage. Differential measurements must be unipolar with the correct voltage applied on pin 3. If a more negative voltage is applied to pin 3, the output current IO will be zero, but no damage will be done.

9. Typical application

The INA139NA/3KG4 is designed for current shunt measurement circuits, but its basic functionality can be used in a variety of circuits. Creative engineers will find many unforeseen uses for measurements and levels shift circuit.