Theory of operation

STPMS1

16/23

Doc ID 16524 Rev 2

The band-gap voltage reference is used as the reference level source for the low-drop

module and for the AD converters. This module produces several bias currents and voltages

for all other analog modules.

The low-drop regulator generates the +3.0 V power supply level. This level is used to power

the DC buffers, pre-amplifier, and AD converter pair in the analog part of the device and

there is a power on reset (POR) detection circuit, which blocks all functions of the STPMS1

In order to enable proper operation of the switched capacitor (SC) section of AD converters,

two DC buffers are added to the device. One is buffering the voltage reference level and the

other is buffering the level of value equal to (VDD-VSS)/2.

The AD converter block is further split into a voltage and current channel. Each channel

consists of a differential pre-amplifier, SC integrator, comparator, amplifier bias block, and all

necessary switches. The voltage channel SC integrator has a gain of 2 and there is no pre-

amplifier block. The current channel SC integrator has a gain of 2 or 8, which can be

selected by MS0 input, and has a pre-amplifier with a gain of 4.

The output of each channel is input to the digital module as

ΣΔ stream.

For the operation of the analog part, a set of five clock signals is provided from the digital

module. These signals derive from the CLK signal. Two of them are used to run the

conversion, the next one is used as the chopper signal for the voltage channel and the last

two are used as chopper signals for the current channel. All these signals are connected to

the control signal module, which consists of standard digital cells powered from an analog

supply. It produces all the necessary signals and switch controls of the AD converters.

Figure 17.

Power supply external connection scheme

AM07836v1

VDD

GND

VDD

GND

MS0

VDD

MS1

VDD

GND

Analog Supply

3.3 -5.0V

100uF

100nF

100nF

AM07836v1

VDD

GND

VDD

GND

MS0

VDD

MS1

VDD

GND

Analog Supply

3.3 -5.0V

100uF

100nF

100nF