STPMS2 datasheet(25/36 Pages) STMICROELECTRONICS

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STPMS2

Theory of operation

DocID16525 Rev 5

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Table 9: TC of the bandgap reference

MS1

Mode

Description

GND

TC = 50 ppm/°C

CLK

TC = -140 ppm/°C

NCLK

TC = 130 ppm/°C

VCC

TC = -40 ppm/°C

MS2 defines the outputs of the device. The STPMS2 sends the sigma-delta stream

synchronous to the CLK signal. The output mode can be configured according to Table 10:

"Control of voltage channel and output signals" as follows:



Sigma-delta stream of the output current channel on DAT and the sigma-delta stream

of the voltage channel on DATn.



Output multiplexed signals, so when CLK = 0, the current channel output sigma-delta

value is set on the DAT pin, and when CLK = 1, the voltage channel output sigma-

delta value is set on the DAT pin. The DATn pin tracks DAT, so DATn = ~DAT.



Sigma-delta stream of the output current channel on DAT and the sigma-delta stream

of the current channel negated on DATn.

Table 10: Control of voltage channel and output signals

MS2

Mode

Description

GND

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

CLK

Voltage channel OFF, DATn = bsCn, DAT = bsC

NCLK

Voltage channel OFF, DATn = bsCn, DAT = bsC

VCC

Voltage channel ON, DATn = bsC, DAT = bsV

MS3 enables or disables the BIST DAC output levels. If enabled (MS3=VCC), the input of

the modulators, disconnected from VIP pin, VIN, CIP and CIN, and connected to the output

of BIST DAC, 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, CIP and CIN. This is the normal operating condition.

Table 11: Selection of hard, soft or test mode and enable of BIST

MS3

Mode

Description

GND

Hard mode, BIST mode OFF

CLK

Soft mode

NCLK

Reserved

VCC

Hard mode, BIST mode ON

9.5

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:

"Pins for SPI communication". All settings of the 40 internal configuration bits can be

changed. The old values remain in the registers until they are overwritten.

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