Data Sheet

ADPA1120

APPLICATIONS INFORMATION

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Rev. 0 | 18 of 19

THERMAL MANAGEMENT

Proper thermal management is critical to achieve the specified

performance and rated operating life. The ADPA1120 can support

both continuous and pulsed operation; however, pulsed biasing

provides better thermal management to maintain a safe channel

temperature (TCHAN). TCHAN (or the die temperature) correlates

closely with the mean time to failure.

Consider a continuous bias case (see Figure 50). When bias is ap-

plied, the TCHAN of the ADPA1120 rises through a turn-on transient

interval and eventually settles to a steady state value. Calculate the

thermal resistance (θJC) of the device as the rise in TCHAN above

the starting base temperature (TBASE ) divided by the total device

PDISS with the following equation:

θJC = tRISE/PDISS

where:

tRISE is the rise in TCHAN of the ADPA1120 above the TBASE (°C).

PDISS is the power dissipation (W) of the ADPA1120.

Figure 50. Channel Temperature Rise for Continuous Bias Condition

Next, consider a pulsed bias case at low duty cycle (see Figure 51).

When bias is applied, the TCHAN of the ADPA1120 can be described

as a series of exponentially rising and decaying pulses. The peak

TCHAN reached during consecutive pulses increases during the

turn-on transient interval, and eventually, this temperature settles to

a steady state condition where the peak TCHAN from pulse to pulse

stabilizes.

Figure 51. Pulsed Bias at Low Duty Cycle