STPMS2

Theory of operation

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8.3.1

Decoder for different modes of operation

The decoder defines the operating mode according to the state of the bootstrap MS0, MS1,

MS2 and MS3 pins. Two different operational modes can be defined:

●

Hard mode: In this case the device configuration is bootstrapped at startup and signals

come from VIN and VIP for voltage channels, and CIP and CIN for current channels or

from internal BIST DAC.

●

Soft mode: In this mode all possible settings from Hard mode are accessible, as well as

additional settings such as dither and chopper signal frequencies and operation (see

Section 8.5).

8.3.2

Generator for clock frequency

Chopper and BIST frequency generator

The Chopper block generates the chopper frequencies and BIST signals for the voltage and

current channels. The BIST DAC output levels are appropriately adjusted for the current

channel according to the gain selection, while for the voltage channel the max DC voltage is

used.

The levels are 300 mV for the voltage channel and 300 mV / 150 mV / 75 mV / 37.5 mV for

the current channel, in accordance with gain settings 2/4/8/16, respectively, when operating

in Soft mode, while 300 mV / 37.5 mV based on gain settings 2/16 when operating in Hard

mode.

Pseudo random

The Pseudo random block generates pseudo random signals for the voltage and current

channels. These random signals are used to implement a dithering technique to de-

correlate the output of the modulators and avoid accumulation points on the frequency

spectrum.

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, which signals are connected to output pins DAT and DATn are selected.

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

In SoftMode, the output signals are selected by 8 configuration bits.

8.4

Hard mode

The STPMS2 operates 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 channels settings

●

output mode settings