REF5010, REF5020, REF5025, REF5030

REF5040, REF5045, REF5050

SBOS410G – JUNE 2007 – REVISED NOVEMBER 2015

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Typical Applications (continued)

The REF5040 is used to drive the REF pin of the ADS8326. Proper selection of Voltage Reference output

capacitor is very important for this design. Very Low ESR creates gain-peaking which degrades SNR of the total

system. If the ESR of the capacitor is not enough, then an additional resistor must be added in series with the

output capacitor. A capacitance of 1

μF can be connected to the NR pin to reduce bandgap noise of the

REF50xx.

SNR Measurements using different RC filters at the output of OPA365, different values of output capacitor for the

REF50xx and different values of capacitors at the TRIM/NR pin are shown in Table 1.

Table 1. Data Acquisition Measurement Results for Different Conditions

TEST CONDITION 1

TEST CONDITION 2

TEST CONDITION 3

OPA365 RC filter

124

Ω, 1 nF

124

Ω, 1 nF

124

Ω, 100 μF

REF5040 Output

10

μF

10

μF + 47 μF

10

μF + 47 μF

capacitor

TRIM /NR pin

0

μF

1

μF

1

μF

capacitor

SNR

86.7 dB

92.8 dB

95

10.2.1.3 Application Curve

Figure 43. FFT plot- Noise floor of Data Acquisition system

20

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