STPMS2

Introduction

Doc ID 16525 Rev 3

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Introduction

The STPMS2 is a device designed to measure electrical line parameters (voltage and

current) via analog signals from voltage sensors (current divider) and current sensors

(inductive Rogowski coil, current transformer or shunt resistors). The device is used

together with a digital signal processing circuit to implement an effective measuring system

for multi-phase power meters.

The device consists of two analog measuring channels, consisting of second-order sigma-

delta modulators with appropriate non-overlapping control signal generator. The STPMS2

also includes a temperature compensated band-gap reference voltage generator, a low-

drop supply voltage stabilizer and minimal digital circuitry that includes BIST (built-in self-

test) structures. In a current signal processing channel, a low-noise preamplifier is included

in front of the sigma-delta converter. All reference voltages (band-gap, AGND) are internally

buffered to eliminate channel crosstalk.

The STPMS2 can operate in fast or low-power mode. In fast mode, a nominal clock

frequency of 4.1 or 4.9 MHz is applied to the clock input. In this mode, signal bandwidth is

specified between 0 and 4 kHz. In low-power mode, the nominal clock is four times slower in

order to reduce the power consumption of the circuit. In low-power mode, the quiescent bias

currents of the preamplifier and sigma-delta integrators are lowered and the signal

bandwidth is narrowed to the frequency bandwidth of 0 to 1 kHz.