9.2.1.1 Design Requirements

A detailed design procedure is based on a design example. For this design example, use the parameters listed

in Table 9-1 as the input parameters.

Table 9-1. Design Example Parameters

DESIGN PARAMETER

VALUE

Input voltage VDD

10V

Heater Voltage VHET (HEATP - HEATM)

30V

Supply decoupling capacitor

1µF

Heater supply decoupling capacitor

1µF

OP-STBL pull-up resistor

10kΩ

OP-STBL pull-up supply

5V

9.2.1.2 Detailed Design Procedure

A bulk capacitor (0.1μF to 10μF) must be connected to the VDD, HEATP and HEATM (when not connected to

GND) pins to improve transient response in the applications where the supply voltage can fluctuate. Connect

an additional 0.1μF capacitor at VDD, HEATP and HEATM pins closer to the device to bypass high frequency

supply noise.

A low ESR (maximum 400mΩ) capacitor of 1μF to 100μF must be connected to the REF_Z pin to provide stable

output. For very low noise applications, special care must be taken with X7R and other MLCC capacitors due

to the piezoelectric effect. More information on how the piezoelectric effect can be explored in systems can be

found in Stress-induced outbursts: Microphonics in ceramic capacitors (Part 1) and Stress-induced outbursts:

Microphonics in ceramic capacitors (Part 2) . Designer must use C0G or film capacitors for noise sensitive

applications. OP-STBL indicates that the on chip heater is regulating the temperature. Connect a pullup resistor

of 10kΩ with suitable logic voltage on this pin. The transient start-up response of the REF80 is shown in REF80

Startup Behavior.

9.2.1.3 Application Curve

Figure 9-2. REF80 Startup Behavior

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REF80

SNAS856A – SEPTEMBER 2024 – REVISED MARCH 2025

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