ZSSC3240CC1B datasheet(32/64 Pages) RENESAS

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ZSSC3240

Datasheet

Nov.27.20

Page 32

6.5

Measurement and Output Options

Sensor or diagnostic measurement results of the ZSSC3240 can be provided in both domains, digital and

analog. Any of the supported digital interfaces and output options can be used as the only active interaction

path, or it can be combined with any of the analog output configurations. For digital communication, only one

interface type can be active and supported (see section 6.4).

Digital communication via SPI and I2C are fully independent of the configuration and application of the

ZSSC3240’s analog outputs. For digital OWI communication combined with analog output, special application

circuits and constraints might have to be considered, as the OWI interface and the analog outputs use the same

pin, AOUT.

6.5.1.

Single Measurements, Digital Raw Results, and SSC Results

The IC generates digital raw values, which are processed by the ZSSC3240-internal math core generating the

SSC-corrected (linearized, temperature-compensated) output signal. See section 6.6.3 for details about the SSC

math, etc. In addition to the SSC-corrected digital measurement results, the ZSSC3240 can provide raw values

without SSC correction for evaluation and/or calibration purposes. The respective results are provided at the

digital interface as a 24-bit wide data word. Raw values and SSC results are MSB-aligned. Raw values are

form

atted as two’s-complement, whereas SSC results are formatted as unsigned absolute value.

Table 24.

Data Format of Raw ADC Readings

Bit-Number

…

Meaning,

Weighting

-20

2-1

2-2

2-3

…

2-21

2-22

2-23

Table 25.

Data Format of Corrected, SSC Results (S and T)

Bit-Number

…

Meaning,

Weighting

2-1

2-2

2-3

…

2-21

2-22

2-23

The ZSSC3240 can process and digitize the following signals:



SM: Direct sensor signal inputs; i.e., perform sensor measurements



AZS: Auto-zero signals for the sensor channel



TM: Direct temperature signal inputs, i.e. perform temperature measurements



AZT: Auto-zero signals for the temperature channel

The internal sequence (in time) of A2D-conversions with both auto-zero measurements enabled is: first is AZS,

second is SM, third is AZT, and forth is TM. The utilization of auto-zero measurements allows further

optimization and reduction of the noise level for the sensor signal in combination with the inherent compensation

of the residual offsets of the analog sensor front-end. If an auto-zero measurement is enabled, then the sensor

signal remains the input for the auto-zero measurement with the gain and ADC set up as for the original signal

measurement, but with swapped inputs and offset configurations of the PGA and ADC such that the following

holds for the resulting raw value:



Sensor raw value with auto-zero: S_raw = 0.5

 (SM – AZS)



Temperature raw value with auto-zero: T_raw = 0.5

 (TM – AZT)

The application benefits with enabled auto-zero measurements are



ZSSC3240 front-end offset cancellation

– residual signal degradation1 or drift for the application is eliminated



Improvement of the signal-to-noise ratio for the raw or SSC-corrected output signal

1 Worst-case IC-offset drift is < 2ppm/day at 125°C.

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