REF50 datasheet(26/52 Pages) TI2

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8.3.6 Output Adjustment Using the TRIM/NR Pin

The REF50xxI, REF50xxAI provides a very accurate, factory-trimmed voltage output. Adjust VOUT using the trim

and noise reduction pin (TRIM/NR, pin 5). Figure 8-5 shows a typical circuit that allows an output adjustment of

±15mV.

GND TRIM/NR

TEMP

VOUT

VIN

DNC

REF50XX

R1 = 10k

R2 = 2k

VSUPPLY

Figure 8-5. VOUT Adjustment Using the TRIM/NR Pin

The REF50xx allows access to the band-gap through the TRIM/NR pin. Placing a capacitor from the TRIM/NR

pin to GND (Figure 8-4) in combination with the internal R3 and R4 resistors creates a low-pass filter. A

capacitance of 1μF creates a low-pass filter with the corner frequency from 10Hz to 20Hz. A low-pass filter

decreases the overall noise measured on the VOUT pin by half. A higher capacitance results in a lower filter

cutoff frequency, further reducing output noise. Using this capacitor increases start-up time.

8.4 Device Functional Modes

8.4.1 Basic Connections

Figure 8-6 shows the typical connections for the REF50xx. TI recommends a supply bypass capacitor ranging

from 1μF to 10μF. Confirm that a output capacitor (CL) is connected from VOUT to GND. For output stability,

verify that the equivalent series resistance (ESR) value of CL less than or equal to 1.5Ω. To minimize noise, the

recommended ESR of CL is from 1Ω and 1.5Ω.

GND

VOUT

TRIM/NR

GND

REF50

TEMP

VIN

+VSupply

DNC

CBYPASS

1µF to 10µF

GND

CL = 1µF to 50µF for REF50xxI, REF50xxAI

CL = 1µF to 100µF for REF50xxEI

Figure 8-6. Basic Connections

8.4.2 Supply Voltage

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, operate the family of references with a supply of

REF50, REF50E

SBOS410O – JUNE 2007 – REVISED OCTOBER 2025

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