STPMS2 datasheet(24/36 Pages) STMICROELECTRONICS

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Theory of operation

STPMS2

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DocID16525 Rev 5

Synchro

In synchro block the synchronization of sigma-delta input streams with strobe signals from

analog part and clock signal is performed.

Mux

In the mux block signals, connected to output pins DAT and DATn, are selected. In hard

mode, the output signals are selected by input pin MS2. In soft mode, the output signals

are selected by 8 configuration bits.

9.4

Hard mode

The STPMS2 works in hard mode when input pin MS3 is connected to GND or VCC, as

described in Table 11. In hard mode, the STPMS2 has four digital input pins (MS0, MS1,

MS2 and MS3) to configure the basic operating parameters:



BIST DAC enable



Temperature curve of reference voltage



Current and voltage channel settings



Output mode settings

In this manner, 128 different combinations are available and they are controlled by MS0,

MS1, MS2 and MS3 pins. MS0 sets the operating mode and amplifier gain selection as

described in Table 8: "Precision mode and input amplifier gain selection" .



MS0 = GND or CLK to select LPR (low precision); fCLK = 1 MHz is the typical input

clock frequency and low power mode is selected.



MS0 = NCLK or VCC to select HPR (high precision); fCLK = 2 or 4 MHz are the typical

input clock frequencies and accuracy is enhanced.

The relative gain of the current channel is selectable between 2 or 16, which defines the

maximum differential voltage on the current channel to ± 300 mV or ± 37.5 mV,

respectively. The voltage channel gain setting is fixed at 2, which defines the maximum

differential voltage on the voltage channel inputs to ± 300 mV.

Table 8: Precision mode and input amplifier gain selection

MS0

Mode

Description

GND

LPR, amplifier GAIN selection g3 = 16

CLK

LPR, amplifier GAIN selection g0 = 2

NCLK

HPR, amplifier GAIN selection g0 = 2

VCC

HPR, amplifier GAIN selection g3 = 16

MS1 defines the temperature compensation (TC) curve of the internal voltage reference of

the STPMS2, as described in Table 9: "TC of the bandgap reference" (characterized by

application). The temperature-compensated reference voltage generator produces VREF =

1.23 V. This generator is implemented as a bandgap generator, whose temperature

compensation curve can be selected by MS1 configuration pin.

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