ADBMS1818ASWAZ-R7 datasheet(74/92 Pages) AD

74 / 92 page

Data Sheet

ADBMS1818

APPLICATIONS INFORMATION

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Rev. B | 74 of 92

Using Nonstandard Cell Input Filters

A cell pin filter of 100 Ω and 10 nF is recommended for all applica-

tions. This filter provides the best combination of noise rejection

and TME performance. In applications that use C pin RC filters

larger than 100 Ω and 10 nF, there may be additional measurement

error. Figure 97 shows how both total TME and TME variation

increase as the RC time constant increases. The increased error

is related to the mux settling. It is possible to reduce TME lev-

els to near data sheet specifications by implementing an extra

single channel conversion before issuing a standard all channel

ADCV command. Figure 98 shows the standard ADCV command

sequence. Figure 98 shows the recommended command sequence

and timing that allow the mux to settle. The purpose of the modified

procedure is to allow the mux to settle at C1/C7/C13 before the

start of the measurement cycle. The delay between the C1/C7/C13

ADCV command and the all channel ADCV command is dependent

on the time constant of the RC being used. The general guidance

is to wait 6τ between the C1/C7/C13 ADCV command and the

all channel ADCV command. Figure 97 shows the expected TME

when using the recommended command sequence.

Figure 97. Cell Measurement TME

Figure 98. ADC Command Order

ADBMS1818ASWAZ-R7 Datasheet(PDF) 74 Page - Analog Devices