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In some applications, the current can flow into the load in both directions. In these cases, a bidirectional amp is often employed due to the ability to measure current in both negative and positive directions, such as in brushed motor control applications. The direction and speed of the motor’s rotation can be determined by measuring the voltage drop across the shunt. Addressing this need, STMicroelectronics developed the TSC2020, a bidirectional current-sense amplifier.
The working principle of a current-sensing amplifier is based on Ohm's law. When load current flows through a shunt resistor (Rshunt) present on inputs, it generates a voltage drop. This voltage is generally small to limit power-dissipation losses. It’s then amplified with an instrumentation amplifier. The resulting output voltage is a voltage that’s proportional to the Ioad current. It can then be processed with an analog-to-digital converter (ADC).
With a precision current-sense amplifier, designers can measure small voltage drops across shunt resistors with minimal error. Small shunt resistors values are necessary to minimize the power dissipation. Thanks to highly accurate current measurements, precision current-sense amplifiers offer improved efficiency and thermal performance.
TSC2020 Current-Sense Amp Tackles 48-V and Higher Systems
Suitable for high- or low-side current sensing, the TSC2020 maintains a wide common-mode voltage range from −4 to 100 V, allowing for use in 48-V systems and at higher voltages. Internal circuitry ensures input offset voltage within ±150 µV that helps to reduce the external shunt resistor size, lowering power dissipation. Its ability to sense very low drop voltages minimizes measurement errors.
Common-mode rejection of at least 100 dB brings consistent accuracy when exposed to fluctuating common-mode voltages in applications such as inline motor control. Also, enhanced PWM rejection delivers high immunity to noise in motor drives and switched-mode power converters.
With 100-V-tolerant inputs and internally fixed gain, the TSC2020 also ensures high accuracy and saves space by eliminating external components typically needed for protection and gain-setting configurations. It’s AEC-Q100 qualified and thus will fit automotive applications such as motor-controlled window lifters, the battery-management system (BMS), and traction inverters.
In addition, saving external components, which reduces the bill of materials, the TSC2020’s fixed gain of 20V/V once again ensures high accuracy and stability with 0.3% gain error and 3.5-ppm/°C drift. No trimming is required.
This device fully operates over the supply voltage range of 2.7 to 5.5 V, and over the industrial temperature range of −40 to 125 °C
The TSC2020, in mass production now, is available in a choice of SO8 and Mini SO8 packages. Pricing starts at $1.20 for 1,000 units. Both industrial- and automotive-grade versions are part of ST’s 10-year longevity program that offers long-term product availability.
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