PS081 datasheet(36/155 Pages) AMSCO

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3-13

PSØ81

One sequence in this example is made of 4 samples, each made of 4 discharge cycles. So in total 1

measurement takes 16 discharge cycles.

Besides the discharging cycles given by the sample there are additional measurements like gain

compensation or fake measurements for better stability. All those measurements together form in

total then a measurement sequence. In other words, a sequence contains all measurements needed

to get the final result. It also defines the total conversion time. For more details on conversion time

please see the chapters ‚Conversion Time‘ 3.5.5 and ‚Modes‘ 3.5.

Of course, the sample size of averaging dominates the update rate. While the resolution is improved

by a factor 1/

√avrate, the maximum update rate is reduced by the factor avrate.

sample size (avrate) k g

Resolution k

Max. update rate m

Also the lowest possible current consumption is influenced by the sample size. It grows by a factor

avrate.

sample size (avrate) kg

Minimum current k

Recommendation: We strongly recommend not to use avrate = 1. In principle it works but the drift

significantly increases and it can be used only for low end resolution applications. The recommended

minimum sample size is avrate = 2. It is also not recommended to use odd numbers at lower avrate

up to 50. E.g., do not use avrate = 7, use instead avrate = 8 or avrate = 6.

Important: At low avrates (<= 32) the factor ps081adjust (Configreg_03, Bit [9:4]) should be set to

2x avrate. Example: avrate = 8 --> set ps081adjust to 16

3.4.6

Resolution and Converter Precision

In this document the terms resolution and converter precision are often used in the same context,

however, there is a difference in their meaning:

Resolution: refers to the digital value which can be displayed (or resolved) within the chip. This

is basically the HB0 register in a 24-bit format, where the MSB is indicating a negative number

(two‘s complement). Expressed in numbers the result can be shown from -8388608 (0x800000)

to +8388607 (0x7FFFFF). One LSB has thereby the valency of 10nV/V (2mV/V divided by

200,000). Example: at 3V the valency of 1 LSB is 10nV/V x 3V = 30nV.

Converter Precision (sometimes also refered to as „accuracy“): this is the accuracy given by

the converter, normally defined by the standard deviation or RMS (root mean square) noise. The

value of the precision is normally given in effective number of bits (ENOB). With PS081 an RMS

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