AD816

REV. B

–13–

Normally, the AD816 will be soldered directly to a copper pad.

Figure 47 plots

θ

to copper pads on both sides of G10 epoxy glass board connected

together with a grid of feedthroughs on 5 mm centers.

This data shows that loads of 100 ohms or greater will usually

not require any more than this. This is a feature of the AD816’s

15-lead power SIP package.

An important component of

θ

package to heatsink. The data given is for a direct soldered

connection of package to copper pad. The use of heatsink

grease either with or without an insulating washer will increase

this number. Several options now exist for dry thermal connec-

tions. These are available from Bergquist as part # SP600-90.

Consult with the manufacturer of these products for details of

their application.

35

30

10

0

2.5k

0.5k

1k

1.5k

2k

25

20

15

AD816AVR, AY

(θ

123

Figure 47. Power Package Thermal Resistance vs. Heat

Sink Area

Other Power Considerations

There are additional power considerations applicable to the

AD816. First, as with many current feedback amplifiers, there is an

increase in supply current when delivering a large peak-to-peak

voltage to a resistive load at high frequencies. This behavior is

affected by the load present at the amplifier’s output. Figure 12

summarizes the full power response capabilities of the AD816

driver. These curves apply to the differential driver applications

(right-hand side of Figure 52). In Figure 12, maximum continu-

ous peak-to-peak output voltage is plotted vs. frequency for

various resistive loads. Exceeding this value on a continuous

basis can damage the AD816.

The AD816 is equipped with a thermal shutdown circuit. This

circuit ensures that the temperature of the AD816 die remains

below a safe level. In normal operation, the circuit shuts down

the AD816 at approximately 180

°C and allows the circuit to

turn back on at approximately 140

°C. This built-in hysteresis

means that a sustained thermal overload will cycle between

power-on and power-off conditions. The thermal cycling typi-

cally occurs at a rate of 1 ms to several seconds, depending on

the power dissipation and the thermal time constants of the

package and heat sinking. Figures 48 and 49 illustrate the ther-

mal shutdown operation after driving OUT1 to the + rail, and

OUT2 to the – rail, and then short-circuiting to ground each

output of the AD816. The AD816 will not be damaged by

momentary operation in this state, but the overload condition

should be removed.

Figure 48. OUT2 Shorted to Ground Through a 2

Ω

Figure 49. OUT1 Shorted to Ground Through a 2

Ω

Ω, R

Ω