STPMS2

Theory of operation

Doc ID 16525 Rev 3

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MS3 enables or disables the BIST DAC output levels.

If enabled (MS3=VCC), the input of the modulators are disconnected from pin VIP, VIN and

CIP, and CIN, and connected to the output of BIST DAC which generates 2 different levels

appropriately adjusted for the current channel 300 mV / 37.5 mV depending on gain settings

2/16, while for the voltage channel, 300 mV is used. This mode is used as auto diagnostic

methodology of good behavior of the two modulators.

When disabled (MS3=GND), the input of the modulators comes from pins VIP, VIN and CIP,

and CIN. This is the normal operating condition.

8.5

Soft mode

The STPMS2 switches to Soft mode when MS3 is connected to CLK. In Soft mode, input

pins MS0, MS1 and MS2 control the serial communication port, as described in Table 12.

This way, all settings of the 40 internal configuration bits can be changed. The old values

remain in the registers until they are overwritten.

Table 10.

Control of voltage channel and output signals

MS2

Mode

Description

GND

0

Voltage channel ON, DATn = ~ [DAT =(CLK) ? bsV : bsC)]

CLK

1

Voltage channel OFF, DATn = bsCn, DAT = bsC

NCLK

2

Voltage channel OFF, DATn = bsCn, DAT = bsC

VCC

3

Voltage channel ON, DATn = bsC, DAT = bsV

Table 11.

Selection of Hard, Soft or Test mode and enable of BIST

MS3

Mode

Description

GND

0

HardMode, BIST mode OFF

CLK

1

Soft mode

NCLK

2

Reserved

VCC

3

HardMode, BIST mode ON

Table 12.

Pins for SPI communication

Pin

Function

Description

MS0

SCL

Clock input

MS1

TDI

Data input

MS2

TDS

Enable

MS3

CLK

SPI operation