PS081 datasheet(86/155 Pages) AMSCO

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PSØ81

In the acam-circuits like those of the evaluation-kit or the examples for solar-quattro scales these in-

sights are already put to practice. When building up your own circuit please make sure you follow the

recommendations as they will contribute to a good overall measurement quality.

4.6.2

Voltage Measurement

An internal bandgap reference is used for measuring the voltage. This is done 40 times per second.

The result is stored in the RAM at address 25, UBATT. It is calculated as Voltage = 2.0 V + 1.6 V*

UBATT/64.

The result can be used for low-battery detection:

the level is set in configuration register low_batt[2:0]:

low_batt

Level (V)

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

Flag flg_ub_low in the status register indicates if the voltage is below the set level .

Power supply rejection: The measured voltage can be used to correct the dependency of the gain

from the voltage. It is switched on by setting configuration bits mult_en_ub = 1 and mult_ub[7:0].

The result of the strain measurement will be corrected according to HB = HB/(1 + UB*[-128 ...

127]/2^21).

EEPROM protection: when the voltage is below 2.4 V the automatic EEPROM write (putepr) is

prohibited. This protects the EEPROM against corrupt data.

Caution: If the supply voltage goes below 2.1 V the voltage measurement will be wrong (the dis-

played value is too high) and the measured values cannot be used. In 1.5 V systems there is no

possibility to measure the supply voltage with PSØ81.

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PS081 Datasheet(PDF) 86 Page - ams AG