Data Sheet

ADPA1122

APPLICATIONS INFORMATION

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Rev. 0 | 16 of 17

THERMAL MANAGEMENT

Proper thermal management is critical to achieve the specified

performance and rated operating life. Pulsed biasing is required to

limit the average power dissipated and to maintain a safe channel

temperature. The channel (or die) temperature correlates closely

with the mean time to failure.

Consider a continuous bias case (see Figure 48). When bias is ap-

plied, the channel temperature (TCHAN) of the device 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 TBASE divided by the total device

PDISS with the following equation:

θJC = tRISE/PDISS

where:

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

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

Figure 48. Channel Temperature Rise for Continuous Bias Condition

Next, consider a pulsed bias case at low duty cycle (see Figure 49).

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

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

channel temperature reached during consecutive pulses increases

during the turn on transient interval and eventually settles to a

steady state condition where peak channel temperatures from pulse

to pulse stabilize.

Figure 49. Pulsed Bias at Low Duty Cycle