AS8501 - Data Sheet

austriamicrosystems

Revision 1.1, 04-April-06

www.austriamicrosystems.com

Page 24 of 40

subregister TRIMBTC

change of reference voltage Uo and TC-value with TRIMBTC bits

Nr.

trimbtc0

TC

Notes

trimbtcs

trimbtc3

trimbtc2

1

trimbtc1

1

mV

ppm/K

0

0

0

0

0

0

Uo

TCo

1),2)

1

0

0

0

0

1

Uo -1*5.2

TCo -1*12.7

1),2)

2

0

0

0

1

0

Uo -2*5.2

TCo -2*12.7

1),2)

..

..

..

..

..

..

..

14

0

1

1

1

0

Uo –14*5.2

TCo -14*12.7

1),2)

15

0

1

1

1

1

Uo –15*5.2

TCo -15*12.7

1),2)

16

1

0

0

0

0

Uo

1),2)

17

1

0

0

0

1

Uo +1*5.2

TCo +1*12.7

18

1

0

0

1

0

Uo +2*5.2

TCo -2*12.7

1),2)

..

..

..

..

..

..

..

..

30

1

1

1

1

0

Uo +14*5.2

TCo -14*12.7

1),2)

31

1

1

1

1

1

Uo +15*5.2

TCo -15*12.7

Notes:

1)

Uo is the reference voltage in mV and TCo is the TC value in ppm/K at TRIMBV = 00000

2)

Every step of TRIMBTC settings brings

S=12.7 ppm/K change in the slope of temperature dependence. So for trimming the temperature coefficient of

value is TCm then the number that should be written into the TRIMBTC for minimum final TC is calculated as

trimBTC=int(TCM/12.7) for positive values and trimBTC=16+int(-TCM/12.7) for negative values.

The absolute voltage is also changed in this way, which must be compensated by bringing back the absolute value by changing the TRIMBV

register. Usually the TRIMBVx=-TRIMBTCx+1 is sufficient. If further accuracy or change of absolute value is necessary it can be adjusted by

making some more measurements and adjustments.

ZZR REGISTER:

ZTR

ZCL

ZTC

20

110

53

TRR

CAR

bit0

bit0

reg.7

reg.6

5

TRR

CAR

data in

bit0

bit0

R/W

188

ZLO

ZLO

Figure 8: Copying of ZCL and ZTR registers into CAR and TRR registers