ZSSC3224 datasheet(39/48 Pages) RENESAS

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ZSSC3224 Datasheet

November 12, 2018

6.7.5 SSC Measurements

After the completion of the calibration procedure, linearized external sensor and temperature readings can be obtained using the commands

AAHEX to AFHEX as described in Table 6.1.

Typically, only one external sensor is used in a single analog configuration using the setup in the SM_config1 MTP register (12HEX). However,

the ZSSC3224 can support a second analog configuration that is set up in the SM_config2 MTP register (16HEX). This might be useful in cases

where only one sensor-ZSSC3224 pair must support the measurand ranges for two different external sensors that have different precisions,

required amplification, and sensor offset.

If a respective switching between setups is to be performed, the SSC coefficients for the alternate external sensor must be handled with one of

the following methods:



The programmed SSC coefficients are not used for the alternate external sensor. The ZSSC3224 performs only a one-to-one transfer, i.e.

no effective digital SSC correction – only a transfer of the auto-zero corrected raw ADC readings to the ZSSC3224 output without any

scaling, etc.



The coefficients are re-programmed each time the analog setup is changed.

SM_config1 is selected as the analog setup register by default, so no specific activation is needed if only SM_config1 is used. If SM_config2

will also be used, the activation command B1HEX must be sent once prior to the measurement request. To switch to using SM_config1, the

activation command B0HEX must be sent prior to use. This activation must be refreshed after any power-on reset or RES pin reset.

6.8

The Calibration Math

6.8.1 Bridge Signal Compensation

The saturation check in the ZSSC3224 detects saturation effects of the internal calculation steps, allowing the final correction output to be

determined despite the saturation. It is possible to get potentially useful signal conditioning results that have had an intermediate saturation

during the calculations. These cases are detectable by observing the status bit 0 for each measurement result. Details about the saturation

limits and the valid ranges for values are provided in the following equations.

The calibration math description assumes a calculation with integer numbers. The description is numerically correct concerning values, dynamic

range, and resolution.

SOT_curve selects whether second-order equations compensate for sensor nonlinearity with a parabolic or S-shaped curve. The parabolic

compensation is recommended for most sensor types.

For the following equations, the terms are as follows:

Corrected sensor reading output via I2C or SPI; range [0HEX to FFFFFFHEX]

S_Raw

Raw sensor reading from ADC after AZ correction; range [-7FFFFHEX, 7FFFFHEX]

Gain_S

Sensor gain term; range [-7FFFFHEX, 7FFFFHEX]

Offset_S

Sensor offset term; range [-7FFFFHEX, 7FFFFHEX]

Tcg

Temperature coefficient gain term; range [-7FFFFHEX, 7FFFFHEX]

Tco

Temperature coefficient offset term; range [-7FFFFHEX, 7FFFFHEX]

T_Raw

Raw temperature reading after AZ correction; range [-7FFFFHEX, 7FFFFHEX]

SOT_tcg

Second-order term for Tcg non-linearity; range [-7FFFFHEX, 7FFFFHEX]

SOT_tco

Second-order term for Tco non-linearity; range [-7FFFFHEX, 7FFFFHEX]

SOT_sens =

Second-order term for sensor non-linearity; range [-7FFFFHEX, 7FFFFHEX]

SENS_shift =

Post-calibration, post-assembly sensor offset shift; range [-7FFFFHEX, 7FFFFHEX]



Absolute value

 ul



Bound/saturation number range from ll to ul, over/under-flow is reported as saturation in the status byte

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