AS8500 - Data Sheet

austriamicrosystems

Revision 1.2, 08-Junel-06

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41

7.2.1

Reference voltage

The ASSP contains a highly sophisticated precision reference voltage. Its typical temperature dependence is a slight parabola shaped curve and is

shown in figure 14. This reference voltage is used mainly for the internal AD-converter, but can also be used for external purposes if the impedance of

the external circuitry is high enough.

The absolute value and its temperature coefficient (TC) is given by the content of the TRR register. This opens the possibility to calibrate the reference

voltage to the optimum absolute value (i.e. 1.28 V) and the TC value to zero thus eliminating fully the production spread.

INTERNAL

TEMPERA-

TURE

AD-

CON-

VERTER

PGA

AUXILIARY

CURRENT

SOURCE

M 12

M 13

M 3

M 10

M 14

CURRENT

SOURCE

M 2

M 1

M 4

M 15

M 8

M 7

M 9

M 6

ETR

ETS

VBAT

RSHH

RSHL

M 5

reference voltage as function of resistance load

1,12

1,14

1,16

1,18

1,20

1,22

1,24

1,26

10

20

30

40

50

60

70

80

90

100

110

resistance load in kOhm

measurement

open loop value

Figure 3: Multiplexer