9.2.1.3 Low Noise Design Recommendations

Any leakage on NR pin capacitor adds up in temperature accuracy. Capacitors with low leakage such as ceramic

cap (COG) or film capacitors are recommended with design. A guard ring can also be added to control the

leakage.

9.2.2 Power Supply Recommendation

The REF54 family of references features a low-dropout voltage. These references can be operated with a supply

of only 250 mV above the output voltage for 5 mA output current conditions. TI recommends a supply bypass

capacitor ranging between 0.1 µF to 10 µF. REF54 family have excellent PSRR (100 dB at 1Khz) which relaxes

the requirement of clean power supply for the designer.

During start-up the REF54 can experience moments of high input current due to the output capacitors. The input

current can momentarily rise to short circuit current ISC. The source needs to have current clamp > ISC to provide

proper startup, otherwise startup is delayed.

9.2.3 Reference Attach With High Precision ADC

High precision ADCs require external precision voltage references to achieve the best SNR and gain drift with

temperature and time. REF54 has flat dynamic impedance at lower frequency. However it's dynamic impedance

increases for higher sampling rate. A low noise - low offset buffer with good bandwidth helps to improve THD

and droop performance to achieve > 18 bit ENOB at higher sampling rate. Figure 9-3 shows evaluation circuit

for ADS1285. Figure 9-4 shows the measurement of peak to peak variation with 0 input (which improves from

ADS1285 result) and Figure 9-5 shows the measurement for VIN = 2.08 V (close to FSR) and we can see that

the peak to peak variation is scaling by < 1.5 times for entire input range with REF54500 reference.

ADS1285

AIN1P

AIN1N

REFN0

REFP0

AVDD

AVSS

AVDD

AIN

AVDD

OPA196

VCOM

VIN

EN

GND

NR

VREF

REF54-Q1

AVDD

AVSS

AVSS

AVSS

AVSS

AVSS

AVSS

Figure 9-3. REF54 -Q1 Attach With ADS1285

www.ti.com

REF54

SNVSCN7 – NOVEMBER 2023

Copyright © 2023 Texas Instruments Incorporated

Submit Document Feedback

23

Product Folder Links: REF54