Mikhail V. Ivanov

A 36 V Programmable Instrumentation Amplifier With Sub-20

A 36 V capable programmable gain instrumentation amplifier (PGA) is presented with sub-20 muV offset, sub-0.2 muV/degC offset drift and a common-mode rejection (CMRR) that exceeds 120 dB at all gain settings without any trimming. It is the first 36 V capable precision PGA implemented in a high-voltage CMOS process, which, in addition, incorporates several additional functions, such as the detection of input and output fault conditions, provisions for improving system-level settling time and an input switch network. All op-amps used in the PGA employ chopper stabilization with a notch filter that removes chopping glitches, leading to low offset and drift and no 1/f noise. The PGA has a total of 22 gain steps (binary steps between 1/8 to 128, each with an optional multiplying factor of 1 or 1.375) with better than 0.1% gain accuracy, < 0.001% nonlinearity and sub-2 ppm/C gain drift. The input switch network, in addition to acting as a 2-channel multiplexer, also enables various system-level diagnostic features. The PGA is implemented in a 0.35 mum CMOS process with a 36 V extension, has a 3.6 times 2.4 mm chip area and consumes a total quiescent current of 3 mA.

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This paper presents two integrated magnetic sensor ICs for isolated current measurement that have a fluxgate magnetometer co-integrated along with circuitry on a die. The integrated fluxgate has a sensitivity of 250 V/T and a 500 ksps readout circuit and requires only 5.4 mW for fluxgate excitation, which is 20x more power-efficient than the state of the art. The fluxgate magnetometer was used to realize the first fully integrated sensor IC for closed-loop current sensing. It achieves a dynamic range of 112 dB and a nonlinearity below 0.03%. A second realization provides a precision magnetic sensor IC that can be used for open-loop and differential-field current sensing. It features a sensor gain variation of 0.04% (1-sigma), a nonlinearity below 0.2%, a bandwidth of 47 kHz, and a dynamic range of 100 dB.

V Offset and a CMRR in Excess of 120 dB at All Gain Settings

This paper presents two integrated magnetic sensor ICs for isolated current sensing. Both employ an integrated fluxgate magnetometer with a sensitivity of 250V/T and a 500ksps readout circuit. Only 5.4mW is required to excite the sensor, which is 20x more power efficient than the state-of-the-art. With an external magnetic core, the resulting closed-loop current sensor IC achieves a dynamic range of 112dB and a non-linearity below 0.03%, while the open-loop current sensor IC has a dynamic range of 100dB and a non-linearity below 0.2%.

Integrated Fluxgate Magnetometer for Use in Isolated Current Sensing

A 36V JFET-input bipolar operational amplifier is presented with a maximum offset drift of 1μV/°C over a temperature range of −40 to 125°C, which represents a 3x improvement on the state-of-the-art. This is achieved with a drift-compensating circuit incorporated in the input stage that relies on a wafer-level 2-tem-perature laser-trimming method. The opamp has a GBW of 11MHz, a flat-band noise of 5.1nV/√Hz, a slew-rate of 20V/μs, a −126dB (0.00005%) total harmonic distortion plus noise (THD+N) ratio, and a quiescent current of 1.8mA. This combination of high slew rate and good noise-to-power ratio is accomplished through the use of a linearized class-AB boosting circuit in the input stage.

An integrated fluxgate magnetometer for use in closed-loop/open-loop isolated current sensing

A 36V precision voltage-to-current converter for 0–24mA loops is presented. It utilizes dynamic element matching (DEM) and an auto-calibration technique to achieve low DC inaccuracy (0.2%) and low DEM ripple (0.007%). Measurement results show that the auto-calibration suppresses the DEM ripple by a factor of 14, thus eliminating the need for a bulky off-chip ripple-suppression filter. The prototype chip is implemented in a 0.35μm CMOS process occupying 0.84mm2. It has a quiescent current of 0.5mA and a rise time of 10.2μs for a 1mA–23mA output step.