AS89010 datasheet(16/42 Pages) AMSCO

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db12348e_V3.11_preliminary_2017-07-06

Page 15 of 41

AS89010

V3.11

5.4.1 Offset of the A/D Converter

Ideally no or a very small amount of offset would be presented in the conversion output. However, an offset

presented in input signal cannot be overcome. If an input leakage current occurs (at printed circuit board

for example), it is possible that input current takes negative sign and makes conversion unable to operate

for very low level currents. In such a case a well-known amount of an internal offset can be introduced in

order to add the positive offset to the A/D transfer characteristic. Therefore, even low level negative

currents can be measured precisely. This option should be set by configuring the ZERO values in OPT

For this case the output of the A/D conversion can be expressed as:

ZERO

CLK

IREF

OUT





(5)

or for SYND Mode:

ZEROSYND

IREF

ZEROSYND

CLK

IREF

OUTINT

TINT

OUT













(6)

ZERO

OUT

: Offset in CONT, CMD and SYNS Mode: 0, 15, 31 or 63 depends on the ZERO values of

OPTREG

ZEROSYND: Offset factor in SYND Mode: TINT·fCLK /27, TINT·fCLK /211 or TINT·fCLK /215 depending on the

ZERO values of OPTREG

The offset generation is activated only for ZERO≠00b. Please note, the internally generated offset has to

be subtracted from the result value by the user specific control program. It will not be performed internally

or automatically

5.4.2 Divider

For the purpose to further expand the measurement ranges an internal implemented digital divider can be

used to scale the result. This may be necessary if the resolution of the conversion is set to a value of >16

bit. If the digital divider is used the conversion result is downscaled according to:

DIV

OUT

DIV 

(7)

DIV

OUT

: Digital output

DIV : Divider factor (2, 4, 8, 16), see Table 11

Therefore the divider acts as digital downscaling feature of the converter gain. It increases the

effective dynamic range of device without changing its sensitivity or integration time.

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