9.3 Power Supply Recommendation

The buried zener reference requires a stable power supply of 10V to 16.5V for stable operation of the REF_Z

pin. Potential difference between HEATP and HEATM pin must be 10V to 42V. HEATP must always be

connected to a positive supply or ground. HEAM must always be connected to a negative supply or ground.

The heater supply must be able to provide high inrush current for fast start-up of the device. TI recommends a

supply bypass capacitor ranging between 0.1µF to 10µF.

9.4 Layout

9.4.1 Layout Guidelines

Section 9.4.2 illustrates an example of a PCB layout (two layer routing) for a data acquisition system using the

REF80. Some key considerations are:

• Noise performance

– Connect low-ESR, 0.1μF ceramic bypass capacitors at VDD, HEATM and HEATP of the REF80.

– Connect 10uF to 100uF class 1 capacitor at REF_Z of the REF80.

– Do not run sensitive analog traces in parallel with digital traces. Avoid crossing digital and analog traces if

possible, and only make perpendicular crossings when absolutely necessary.

• Thermal performance

– The layout must minimize the heat dissipation to maintain good thermal resistance for REF80.

– Use minimum copper to route VDD, REF_Z, REF_GND signal.

– Use copper as per current requirement for HEATP and HEATM pin.

– Avoid direct copper pours underneath the package.

– A shield around the device is recommended to achieve best heater regulation.

• Seebeck effect

– Avoid multiple metal-metal junction to minimize Seebeck effect.

• Long term stability performance

– Provide strain relief directly to pins as shown in the Layout Example.

– Provide cuts near to the pin, perpendicular to the pins and corners.

– Avoid single point strain accumulation.

9.4.2 Layout Example

Figure 9-6. Top Layer Layout example for REF80

Figure 9-7. Bottom Layer Layout example for

REF80

REF80

SNAS856A – SEPTEMBER 2024 – REVISED MARCH 2025

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