8.3 Feature Description

8.3.1 Output Current

The BUF634A can deliver up to ±250-mA continuous output current. Internal circuitry limits the output current to

approximately ±350 mA. Care must be taken to limit the output voltage swing for a given load resistance to avoid

limiting the output current and degrading linearity; see Figure 9-8. For many applications, however, the

continuous output current is limited by thermal effects. The output voltage swing capability varies with junction

temperature and output current; see Figure 7-17 and Figure 7-18. Care must be taken to operate the device

below the maximum-recommended junction temperature in applications using this buffer in wide-bandwidth

mode with a wide supply voltage and large output current to avoid permanent damage to the device.

8.3.2 Thermal Shutdown

Power dissipated in the BUF634A causes the junction temperature to rise. A thermal protection circuit in the

BUF634A disables the output when the junction temperature reaches approximately 180°C. When the thermal

protection is activated, the output stage is disabled and the output current is limited, allowing the device to cool.

Quiescent current is approximately 12 mA during thermal shutdown. When the junction temperature cools to

approximately 160°C, the output circuitry is again enabled. This process can cause the protection circuit to cycle

on and off with a period ranging from a fraction of a second to several minutes or more, depending on package

type, signal, load, and thermal environment.

The thermal protection circuit is designed to prevent damage during abnormal conditions. Any tendency to

activate the thermal protection circuit during normal operation is a sign of an inadequate heat sink or excessive

power dissipation for the package type.

8.3.3 ESD Protection

As shown in Figure 8-1, all device pins are protected with internal ESD protection diodes to the power supplies.

These diodes provide moderate protection to input overdrive voltages above the supplies. The protection diodes

can typically support 10-mA continuous currents. Current limiting series resistors must be added at the inputs if

common-mode voltages higher than the supply voltages are possible. Keep these resistor values as low as

flowing through the ESD diode. Restrict any current flowing through the ESD diodes to less than 10 mA.

Power Supply

ESD Cell

BW

V+

V±

Figure 8-1. Internal ESD Protection

BUF634A

SBOS948D – FEBRUARY 2019 – REVISED SEPTEMBER 2020

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