REF35-Q1

CIN

GND

VIN

EN

NR

VREF

GND

Optional

CL

High-pass

Filter

Fc = 10Hz

G = 11

Amplifier

G = 11

Supply

Spectrum

Analyzer

Figure 8-11. Broadband Noise Test Setup

For noise sensitive designs, a low-pass filter can be used to reduce broadband noise output noise levels by

removing the high frequency components. When designing a low-pass filter, take special care to make sure the

output impedance of the filter does not degrade AC performance. This can occur in RC low-pass filters where a

large series resistance can impact the load transients due to output current fluctuations. The REF35-Q1 device

also offers noise reduction functionality by adding an optional capacitor between NR (pin 5) and ground pins.

Figure 8-12 and Figure 8-13 show the noise spectrum for REF35250 and REF35500 devices respectively across

various NR pin capacitance.

Frequency (Hz)

10

100

1000

10000

100000

0

200

400

600

800

1000

CL = 0.1uF

CL = 1uF

CL = 10uF

Figure 8-12. Noise Spectrum 10 Hz to 100 kHz

(VREF = 2.5 V)

Frequency (Hz)

10

100

1000

10000

100000

0

400

800

1200

1600

2000

CL = 0.1uF

CL = 1uF

CL = 10uF

Figure 8-13. Noise Spectrum 10 Hz to 100 kHz

(VREF = 5 V)

8.6 Power Dissipation

The REF35-Q1 voltage references are capable of source up to 10 mA and sink up to 5 mA of load current

across the rated input voltage range. However, when used in applications subject to high ambient temperatures,

the input voltage and load current must be carefully monitored to ensure that the device does not exceeded

its maximum power dissipation rating. The maximum power dissipation of the device can be calculated with

Equation 3:

J

A

D

JA

T

T

P

R

T

u

(3)

where

• PD is the device power dissipation

• TJ is the device junction temperature

• TA is the ambient temperature

• RθJA is the package (junction-to-air) thermal resistance

Because of this relationship, acceptable load current in high temperature conditions may be less than the

maximum current-sourcing capability of the device. In no case should the device be operated outside of its

maximum power rating because doing so can result in premature failure or permanent damage to the device.

REF35-Q1

SNAS845 – AUGUST 2023

www.ti.com

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