-2V

+2V

+5V

NOTE: Bypass capacitors not shown.

R

1

10kW

R

2

10kW

-5V

OPA735

+5V

DNC

TEMP

V

OUT

V

IN

GND

DNC

NC

TRIM/NR

REF5020

1 F

m

REF5020-EP, REF5025-EP, REF5040-EP, REF5050-EP

www.ti.com

SBOS471B – APRIL 2010 – REVISED JUNE 2015

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The REF50xx devices are low-noise, precision bandgap voltage references that are specifically designed for

excellent initial voltage accuracy and drift. View the Functional Block Diagram of the REF50xx.

When designing circuits with a voltage reference, output noise is one of the main concerns. The main source of

voltage noise in the reference voltages originates from the bandgap and output amplifier, which contribute

significantly to the overall noise. During the design process, it is important to minimize these sources of voltage

noise.

8.2 Typical Applications

8.2.1 Negative Reference Voltage

For applications requiring a negative and positive reference voltage, the REF50xx and OPA735 can be used to

provide a dual-supply reference from a 5-V supply. Figure 25 shows the REF5020 used to provide a 2.5-V supply

reference voltage. The low-drift performance of the REF50xx complements the low offset voltage and zero drift of

the OPA735 to provide an accurate solution for split-supply applications. Care must be taken to match the

Figure 25. The REF5020 and OPA735 Create Positive and Negative Reference Voltages

8.2.1.1 Design Requirements

When using REF50xx in the design, it is important to select proper capacitive load that will not create gain

peaking adding noise to the output voltage. At the same time, the capacitor must be selected to provide required

filtering performance for the system. In addition, input bypass capacitor and noise reduction capacitors must be

added for optimum performances.

8.2.1.2 Detailed Design Procedure

Proper design procedure will require first to select output capacitor. If the ESR of the capacitor is not in 1-

Ω

range additional resistor must be added in series with the load capacitor. Next, add a 1-µF capacitor to the NR

pin to reduce internal noise of the REF50xx. Measuring output noise will confirm if the design has met the initial

target.

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Product Folder Links: REF5020-EP REF5025-EP REF5040-EP REF5050-EP