ZSSC3224 datasheet(39/51 Pages) IDT

39 / 51 page

ZSSC3224 Datasheet

October 24, 2016

The memory integrity checksum (referred to as CRC) is generated through a linear feedback shift register with the

following polynomial:

g(x) = x

16 + x15 + x2 + 1

with the initialization value: FFFFHEX.

If the CRC is valid, then the “Memory Error” status bit is set to 0.

3.7.

Calibration Sequence

Calibration essentially involves collecting raw signal and temperature data from the sensor-ZSSC3224 system for different

known sensor-element values (i.e., for a resistive bridge or an absolute voltage source) and temperatures. This raw data

can then be processed by the calibration master (assumed to be

the user’s computer), and the calculated calibration

coefficients can then be written to on-chip memory.

Here is a brief overview of the three main steps involved in calibrating the ZSSC3224.

Assigning a unique identification to the ZSSC3224. This identification is written to shadow RAM and programmed

in MTP memory. This unique identification can be stored in the two 16-bit registers dedicated to the customer ID

(00HEX and 01HEX; see Table 3.5). It can be used as an index into a database stored on the calibration PC. This

database will contain all the raw values of the connected sensor-element readings and temperature readings for

that part, as well as the known sensor-element measurand conditions and temperature to which the sensor-

element was exposed.

Data collection. Data collection involves getting uncorrected (raw) data from the external sensor at different

known measurand values and temperatures. Then this data is stored on the calibration master using the unique

identification of the device as the index to the database.

Coefficient calculation and storage in MTP memory. After enough data points have been collected to calculate all

the desired coefficients, the coefficients can be calculated by the calibration master. Then the coefficients can be

programmed to the MTP memory.

Result. The sensor signal and the characteristic temperature effect on output will be linearized according to the setup-

dependent maximum output range.

It is essential to perform the calibration with a fixed programming setup during the data collection phase. In order to

prevent any accidental incorrect processing, it is further recommended that the MTP memory setup is kept stable during

the entire calibration process as well as in the subsequent operation. A ZSSC3224 calibration only fits the setup used

during its calibration. Changes in functional parameters after a successful calibration can decrease the precision and

accuracy performance of the ZSSC3224 as well as of the entire application.

The ZSSC3224 supports operation with different sensor setups by means of the SM_config1 and SM_config2 registers.

However, only one calibration coefficient set is supported. Therefore, either an alternative ZSSC3224-external signal

calibration using the alternate SM_config settings must be performed to ensure that the programmed SSC coefficients are

valid for both setups, or a full reprogramming of the SSC coefficients must be performed each time the sensor setup is

changed. The selection of the external sensor setup (i.e., the AFE configuration) can be done with the interface

commands B0HEX and B1HEX (see Table 3.1).

ZSSC3224 Datasheet(PDF) 39 Page - Integrated Device Technology