ADPA1107ACPZN-R7 datasheet(19/20 Pages) AD

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Data Sheet

ADPA1107

Rev. 0 | Page 19 of 20

THERMAL MANAGEMENT

Proper thermal management is critical to achieve the specified

performance and rated operating life. Pulsed biasing limits

the average power dissipated and maintains a safe channel

temperature. The channel (or die) temperature correlates

closely with the mean time to failure (MTTF).

Consider a continuous bias condition (see Figure 52). When

bias is applied, the channel temperature (TCHAN) of the device

rises through a turn on transient interval and eventually settles

to a steady state value. The θJC of the device is the rise in TCHAN

above the starting TBASE divided by the total device PDISS, which is

calculated by

θJC = tRISE/PDISS

(1)

where:

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

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

tRISE = θJC × PDISS

TCHAN

TBASE

TIME

Figure 52. Channel Temperature Rise for Continuous Bias Condition

Next, consider a pulsed bias condition at a low duty cycle (see

Figure 53). 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.

tRISE = θJC × PDISS

TCHAN

TBASE

POWER DISSIPATED

DURING THE PULSE

TIME

Figure 53. Pulsed Bias Condition at a Low Duty Cycle

Table 7 shows the thermal resistance values for various pulse

conditions.

Table 7. Pulse Settings and Thermal Resistance Values

Pulse Settings

θJC (°C/W)

Pulse Width (µs)

Duty Cycle (%)

100

1.72

100

1.76

500

2.10

Narrower pulse widths and/or lower duty cycles can result in

greater reliability.

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