Current Sensing

The circuit shown in Figure 1 monitors current in systems with high positive common-mode dc voltages of up to +500 V with less than 0.2% error. The load current passes through a shunt resistor, which is external to the circuit. The shunt resistor value is chosen so that the shunt voltage is approximately 500 mV at maximum load current.

The AD8212 accurately amplifies a small differential input voltage in the presence of large positive common-mode voltages greater than 500 V when used in conjunction with an external PNP transistor.

Galvanic isolation is provided by the ADuM5402 quad channel isolator. This is not only for protection but to isolate the downstream circuitry from the high common-mode voltage. In addition to isolating the output data, the ADuM5402 digital isolator can also supply isolated +3.3 V for the circuit.

The measurement result from the AD7171 is provided as a digital code utilizing a simple 2-wire, SPI-compatible serial interface.

This combination of parts provides an accurate high voltage positive rail current sense solution with a small component count, low cost, and low power.

The AD8418 is a high voltage, high resolution current shunt amplifier. It features an initial gain of 20 V/V, with a maximum ±0.15% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. The AD8418 offers excellent input common-mode rejection from −2 V to +70 V. The AD8418 performs bidirectional current measurements across a shunt resistor in a variety of automotive and industrial applications, including motor control, battery management, and solenoid control.

The AD8418 offers breakthrough performance throughout the −40°C to +125°C temperature range. It features a zero drift core, which leads to a typical offset drift of 0.1 μV/°C throughout the operating temperature range and the common-mode voltage range. The AD8418 is fully qualified for automotive applications and includes EMI filters and patented circuitry to enable output accuracy with pulse-width modulation (PWM) type input common-mode voltages. The typical input offset voltage is ±200 μV. The AD8418 is offered in 8-lead MSOP and SOIC packages.

The AD8418A is a high voltage, high resolution current shunt amplifier. It features an initial gain of 20 V/V, with a maximum ±0.15% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. The AD8418A offers excellent input common-mode rejection from −2 V to +70 V. The AD8418A performs bidirectional current measurements across a shunt resistor in a variety of automotive and industrial applications, including motor control, power management, and solenoid control.

The AD8418A offers breakthrough performance throughout the −40°C to +150°C temperature range. It features a zero drift core, which leads to a typical offset drift of 0.1 μV/°C throughout the operating temperature range and the common-mode voltage range. The AD8418A is qualified for automotive applications. The device includes EMI filters and patented circuitry to enable output accuracy with pulse-width modulation (PWM) type input common-mode voltages. The typical input offset voltage is ±100 μV. The AD8418A is offered in an 8-lead MSOP and an 8-lead SOIC_N package with a 10-lead MSOP pinout option engineered for failure mode and effects analysis (FMEA).

Applications

• High-side current sensing in
  
  • Motor controls
  • Solenoid controls
  • Power management
• Low-side current sensing
• Diagnostic protection

The AD8417 is a high voltage, high resolution current shunt amplifier. It features an initial gain of 60 V/V, with a maximum ±0.3% gain error over the entire temperature range. The buffered output voltage directly interfaces with any typical converter. The AD8417 offers excellent input common-mode rejection from −2 V to +70 V. The AD8417 performs bidirectional current measurements across a shunt resistor in a variety of automotive and industrial applications, including motor control, power management, and solenoid control.

The AD8417 offers breakthrough performance throughout the −40°C to +150°C temperature range. It features a zero drift core, which leads to a typical offset drift of 0.1 µV/°C throughout the operating temperature range and the common-mode voltage range. The AD8417 is qualified for automotive applications. The device includes EMI filters and patented circuitry to enable output accuracy with pulse-width modulation (PWM) type input common-mode voltages. The typical input offset voltage is ±200 µV. The AD8417 is offered in 8-lead MSOP and SOIC packages.

Applications

• High-side current sensing in
  • Motor controls
  • Solenoid controls
  • Power management
• Low-side current sensing
• Diagnostic protection

The AD7606/AD7606-6/AD7606-4 are 16-bit, simultaneous sampling, analog-to-digital data acquisition systems (DAS) with eight, six, and four channels, respectively. Each part contains analog input clamp protection, a second-order antialiasing filter, a track-and-hold amplifier, a 16-bit charge redistribution successive approximation analog-to-digital converter (ADC), a flexible digital filter, a 2.5 V reference and reference buffer, and high speed serial and parallel interfaces.

The AD7606/AD7606-6/AD7606-4 operate from a single 5 V supply and can accommodate ±10 V and ±5 V true bipolar input signals while sampling at throughput rates up to 200 kSPS for all channels. The input clamp protection circuitry can tolerate voltages up to ±16.5 V. The AD7606 has 1 MΩ analog input impedance regardless of sampling frequency. The single supply operation, on-chip filtering, and high input impedance eliminate the need for driver op amps and external bipolar supplies. The AD7606/AD7606-6/AD7606-4 antialiasing filter has a 3 dB cutoff frequency of 22 kHz and provides 40 dB antialias rejection when sampling at 200 kSPS. The flexible digital filter is pin driven, yields improvements in SNR, and reduces the 3 dB bandwidth.

Applications

• Power-line monitoring and protection systems
• Multiphase motor control
• Instrumentation and control systems
• Multiaxis positioning systems
• Data acquisition systems (DAS)

The AD7403 is a high performance, second-order, Σ-Δ modulator that converts an analog input signal into a high speed, single-bit data stream, with on-chip digital isolation based on Analog Devices, Inc., iCoupler^® technology. The AD7403 operates from a 5 V (V_DD1) power supply and accepts a differential input signal of ±250 mV (±320 mV full-scale). The differential input is ideally suited to shunt voltage monitoring in high voltage applications where galvanic isolation is required.

The analog input is continuously sampled by a high performance analog modulator, and converted to a ones density digital output stream with a data rate of up to 20 MHz. The original information can be reconstructed with an appropriate digital filter to achieve 88 dB signal to noise ratio (SNR) at  78.1 kSPS. The serial input/output can use a 5 V or a 3 V supply (V_DD2).

The serial interface is digitally isolated. High speed complementary metal oxide semiconductor (CMOS) technology, combined with monolithic transformer technology, means the on-chip isolation provides outstanding performance characteristics, superior to alternatives such as optocoupler devices. The AD7403 device is offered in a 16-lead, wide-body SOIC package and has an operating temperature range of −40°C to +125°C. The AD7403-8 device is offered in an 8-lead, wide-body SOIC package and has an operating temperature range of −40°C to +105°C.

Applications

• Shunt current monitoring
• AC motor controls
• Power and solar inverters
• Wind turbine inverters
• Data acquisition systems
• Analog-to-digital and opto-isolator replacements