ZSSC3281BC3R datasheet(32/102 Pages) RENESAS

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ZSSC3281 Datasheet

R33DS0020ED0100 Rev. 1.0

Jun.13.22

Page 32

Because most sensor applications also require other auxiliary measurements, the assignment of the AZ

measurement to the group of auxiliary measurements helps to reduce the worst case measurement latency on the

main bridge sensor. This is because the SM- slot as needed in configuration of Figure 21, can be omitted.

The lowest measurement latency is achieved with

the “SM- only” configuration in Figure 23. However, this is only

true if no other auxiliary measurements are needed for the desired sensor application.

A further influence on the overall measurement time has the input settling time, which is required depending on

the output resistance of the external sensors, respective capacitive loads on the signal lines and the ADC

resolution selected by the user. The input settling time is always inserted before an ADC conversion starts and

can be configured in the GUI for main bridge measurements via Configure\AFE\Bridge\SetTime[µs] and for

auxiliary temperature measurements via Configure\AFE\Temperature\SetTime[µs].

Considering achievable measurement latencies and noise performance, configuration in Figure 21 is better when

higher ADC resolutions are required or for sensor configurations with fast input settling, while configuration in

Figure 22 and Figure 23 are preferable when lower ADC resolutions become selected or for sensor configurations

requiring long input settling times (bridge settling time has a considerable impact on the timing budget).

4.6.2.

Auxiliary Measurement Configuration

The supported auxiliary measurements are:



Auto-zero for internal signal path



Temperature on sensor input T1



Temperature on sensor input T2



Temperature on sensor input T3



Internal PTAT



AFE diagnostic checks

Sensor connection checks for all external sensors (Short to TOPx pin or BOTx pin and Open)

Bridge sensor leakage to VSS in Thermocouple/Thermopile operation mode of the AFE

Bridge signal range check

AFE gain and offset drift supervision via internal reference DAC

They can be activated in the GUI via tabs Configure\AFE\Sequencer, Configure\AFE\Temperature Selection and

Diagnostic\Sensor/AFE.

4.6.3.

Deterministic Input Step Response with SM+/SM- Configuration

As described in section 4.6.1, sensor configurations with fast input settling or applications requiring higher ADC

resolutions are better served with the SM+/SM- scheme for the main bridge measurement. For the following step

response consideration, the below application example is used:



Sensor Measurement (non-inverted)



Sensor Measurement (inverted)



Auxiliary Measurement (e.g. for sensor temperature)



Note: SM+ and SM- can be exchanged yielding to the same result

SM+

aux i

SM -

SM+

aux i

SM -

standard config

Figure 24: SM+/SM- Configuration

The worst-case input to output latency consists of:



4 sensor A2D-conversion times (duration depending on selected ADC resolution)



1 auxiliary conversion time (fixed duration, based on longest auxiliary conversion timing)



1 SSC calculation

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