Technical information｜Integrated shunt solution with simple design, low drift and small size

Driven by demands for automation, convenience and sustainability, advances in electrification require more sensors, power electronics and processors to reliably and accurately sense and react to their surroundings . Continuously finding ways to reduce solution size, optimize and monitor power consumption is no easy task.

For 20 years, our engineers have been developing current sense amplifiers and digital power monitors to help you find ways to measure system health and monitor power consumption, protect your system from overcurrent conditions, and perform dynamic measurements to adjust control loops, thereby improving efficiency.

While integrated shunt products are not new, what is new is their ability to combine simplicity, low drift, small size and low cost . Texas Instruments' EZShunt™ technology eliminates the need for external shunt resistors and uses the leadframe within the package as a shunt (shown in Figure 1). EZShunt products use temperature compensation algorithms to compensate for the drift of traditional copper leadframes (which can be as high as 3,600ppm/°C). Standard shunt resistors have a drift range of 50ppm/°C to 175ppm/°C. In comparison, EZShunt products can achieve total solution drift as low as 25ppm/°C.

Figure 1: Chip rendering demonstrating how the package leadframe can be used as a shunt.

Digital EZShunt products can significantly reduce design size. For example, the INA700 digital power monitor reduces component area size by 84% compared to a similar wafer-level packaged digital power monitor plus a 1206 shunt.

In addition, digital EZShunt products provide multi-mode detection of current, power, energy, charge, bus voltage and temperature to reduce the burden on the microcontroller (MCU). Performing these calculations on-chip prevents the MCU from spending unnecessary clock cycles on these tasks. There are also alarm pins for reporting diagnostics or indicating when analog-to-digital conversion is complete, reducing the need for the MCU to continuously poll the product to extract results.

For high voltage and current carrying capabilities , the 6mm x 6mm Quad Flat No-Lead package (package identifier DEK) is capable of carrying 75ADC current at 25°C (shown in Figure 2). The INA780A, INA780B and INA781 digital power monitors have common-mode voltage capability up to 85V.

Figure 2: Continuous current capability of DEK packages (INA780A, INA780B, INA781)

EZShunt products also eliminate the layout complexity of Kelvin connections (shown in Figure 3) because they either connect the shunt internally to the input or interpret the shunt's Kelvin connection on an external pin.

Figure 3: INA780 block diagram showing Kelvin connection pins SH+ and SH–

TI's new EZShunt technology brings simplicity, low cost, low drift and small size to a field of current sensing that is expanding with advances in many market segments. The product family covers a wide range of voltages, currents, output types (analog and digital) and accuracy ranges to help meet design needs such as optimizing full scale range or reducing power consumption.