10 Power Supply Recommendations

The BUF634A is intended for operation on supplies ranging from 4.5 V to 36 V (±2.25 V to ±18 V). At low power-

supply conditions, such as ±2.25 V, the output swing may be limited. See the output voltage range specifications

in the Electrical Characteristics tables for additional information. The BUF634A can be operated on single-sided

supplies, split, and balanced bipolar supplies or unbalanced bipolar supplies. Operating from a single supply can

have numerous advantages. With the negative supply at ground, the DC errors resulting from the –PSRR term

can be minimized. Minimize the distance (< 0.1 in.) from the power-supply pins to high-frequency, 0.1-µF

decoupling capacitors. A larger capacitor (10 µF typical) is used along with a high-frequency, 0.1-µF supply-

decoupling capacitor at the device supply pins. For single-supply operation, only the positive supply has these

capacitors. When a split-supply is used, use these capacitors from each supply to ground. If necessary, place

the larger capacitors further from the device and share these capacitors among several devices in the same area

of the PCB.

10.1 Power Dissipation and Thermal Considerations

The BUF634A includes automatic thermal shutoff protection. This protection circuitry shuts down the amplifier if

the junction temperature exceeds approximately 180°C. When the junction temperature decreases to

approximately 160°C, the buffer turns on again. The package and the PCB dictate the thermal characteristics of

the device. Maximum power dissipation for a particular package is calculated using the following formula.

max

A

D max

JA

T

T

P

T

(1)

where

The thermal coefficient for the thermal pad integrated circuit packages are substantially improved over the

traditional SOIC package. The data for the thermal pad packages assume a board layout that follows the thermal

pad package layout guidelines referenced above and detailed in the PowerPAD™ Thermally Enhanced Package

application report. If the thermal package integrated circuit package is not soldered to the PCB, the thermal

impedance increases substantially and may cause serious heat and performance issues.

When determining whether or not the device satisfies the maximum power dissipation requirement, make sure to

consider not only quiescent power dissipation, but dynamic power dissipation. Often times, this dissipation is

difficult to quantify because the signal pattern is inconsistent, but an estimate of the RMS power dissipation

provides visibility into a possible problem.

BUF634A

SBOS948D – FEBRUARY 2019 – REVISED SEPTEMBER 2020

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