Load current vs. ambient temperature and airflow rates are given in Fig. 1 and Fig. 2 for vertical and horizontal converter
mountings. Ambient temperature was varied between 25°C and 85°C, with airflow rates from 30 to 500 LFM
(0.15 to 2.5 m/s). For each set of conditions, the maximum load current was defined as the lowest of:
(i) The output current at which any FET junction temperature does not exceed a maximum specified temperature of
120 °C as indicated by the thermographic image, or
(ii) The temperature of the inductor does not exceed 120 °C, or
(iii) The nominal rating of the converter (40 A).
During normal operation, derating curves with maximum FET temperature less or equal to 120 °C should not be exceeded.
Temperature at the thermocouple location shown in Fig. H should not exceed 120 °C in order to operate inside the
derating curves.
Fig. 3 shows the efficiency vs. load current plot for ambient temperature of 25 ºC, airflow rate of 300 LFM (1.5 m/s) with
vertical mounting and input voltages of 36 V, 48 V, and 72 V. Also, a plot of efficiency vs. load current, as a function of
ambient temperature with Vin = 48 V, airflow rate of 200 LFM (1 m/s) with vertical mounting is shown in Fig. 4.
Fig. 5 shows the power dissipation vs. load current plot for Ta = 25 ºC, airflow rate of 300 LFM (1.5 m/s) with vertical mounting
and input voltages of 36 V, 48 V, and 72 V. Also, a plot of power dissipation vs. load current, as a function of ambient
temperature with Vin = 48 V, airflow rate of 200 LFM (1 m/s) with vertical mounting is shown in Fig. 6.
Output voltage waveforms, during the turn-on transient using the ON/OFF pin for full rated load currents (resistive load) are
shown without and with external load capacitance in Error! Reference source not found. and Figure 7, respectively.
Fig. 10 show the output voltage ripple waveform, measured at full rated load current with a 10 µF tantalum and 1 µF ceramic
capacitor across the output. Note that all output voltage waveforms are measured across a 1 µF ceramic capacitor.
The input reflected ripple current waveforms are obtained using the test setup shown in Fig 11. The corresponding
waveforms are shown in Figs. 12-13.
