AS8500 - Preliminary Data Sheet

austriamicrosystems

Revision 1.1, 04-April-06

www.austriamicrosystems.com

Page 21 of 39

7.5.6

CAR calibration register ( 110 bits )

The aim of the calibration register is to hold the calibration constants that are used by the internal DSP for the correction

of each measurement (for the factory calibrated version AS8501). At power-up sequence the Zener-Zap subregister ZCL

default setting is copied into the CAR register. The register can be read or written in mode 8 via the SDI bus at any time.

In particular for the AS8500, which is not factory calibrated it is intended to overwrite the default setting with external data

defined by the user.

Nr.

CAR bits

109-99 98-88

87-77

76-66

65-55

54-44

43-33

32-22

21-11

10-0

NOTE

0

Subregister

CGI1

CGI2

CGI3

CGI4

1

default

1548

1548

1548

0

1548

2047

2047

1548

1548

Notes:

1)

Calibration register is composed of the following constants each having 11 bits:

CGI1, CGI2, CGI3, CGI4, CAU0, CAU1, CAU2, CAU3, CAU4, CAU5

2)

Decimal default value of the calibration constant for voltage and current is calculated

using formula: CGdef=Nmax/NADdef=(Vref*1024)/(Vin*Gmax)=1548

7.5.7

TRR trimming register ( 20 bits )

In the TRR register the calibration constants for the reference voltage, for the amplifier-offset trim and for the current source setting are stored.

At power-up sequence the Zener-Zap subregister ZTR is loaded into the TRR register. This register can be read or written in mode 8 via the

SDI bus. In particular it is possible to write preliminary calibration constants into TRR or overwrite the loaded ZTR data, if a calibration has been

changed. The trimming of the TRR-registors is usually done at the factory before supplying the part.

Nr.

TRR bits

19-15

14-10

9-5

4-0

NOTE

0

Subregister

TRIMC

TRIMA

TRIMBV

1

default

4

typ 0 or 1

16

17

Notes:

1)

writing into TRR register is done as usual with the MSB first

subregister TRIMC

change of current source output with TRIMC bits

Nr.

trimc0

dI/Io

Notes

trimcs

trimc3

trimc2

trimc1

%

0

0

0

0

0

0

0

1),2)

1

0

0

0

0

1

-1*2.3

1),2)

2

0

0

0

1

0

-2*2.3

1),2)

..

..

..

..

..

..

..

14

0

1

1

1

0

–14*2.3

1),2)

15

0

1

1

1

1

–15*2.3

1),2)

16

1

0

0

0

0

16*2.3

1),2)

17

1

0

0

0

1

15*2.3

18

1

0

0

1

0

14*2.3

1),2)

..

..

..

..

..

..

..

30

1

1

1

1

0

2*2.3

1),2)

31

1

1

1

1

1

1*2.3

Notes:

1)

Io is the current in µA at TRIMC = 00000

2)

The output current of the internal current source can be controlled in a wide range via the bit setting in CRG. In some applications it may be

necessary to trim the current in the rang of +/- 30% for an optimum result of the external temperature measurement. This trimming is achieved

with writing into subregister TRIMC of the TRR register. The trimming is done in % for all ranges selected in CRG register.