REF5025IDGKT datasheet(29/49 Pages) TI1

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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 equivalent series resistance (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 1μF can be connected to the NR pin to

reduce band-gap noise of the REF50xx.

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

the REF50xx and different values of capacitors at the TRIM/NR pin are shown in Table 9-1.

Table 9-1. Data Acquisition Measurement Results for Different Conditions

TEST CONDITION 1

TEST CONDITION 2

OPA365 RC filter

124Ω, 1nF

REF5040 output capacitor

10μF

10μF + 47μF

TRIM/NR pin capacitor

0μF

1μF

SNR

86.7dB

92.8dB

9.2.1.3 Application Curve

Figure 9-2. FFT Plot-Noise Floor of Data Acquisition System

10 Power Supply Recommendations

The REF50xx family of voltage references features extremely low dropout voltage. With the exception of the

REF5020, which has a minimum supply requirement of 2.7V, these references can be operated with a supply of

200mV more than the output voltage in an unloaded condition. For loaded conditions, a typical dropout voltage

versus load plot is provided in Figure 6-6. TI recommends a supply bypass capacitor ranging from 1μF to

50μF for REF50xxI and REF50xxAI. TI recommends a supply bypass capacitor ranging from 1μF to 100μF for

REF50xxEI.

www.ti.com

REF50, REF50E

SBOS410N – JUNE 2007 – REVISED MARCH 2025

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