SSQE48T07050 DC-DC Converter Data Sheet
36-75 VDC Input; 5.0 VDC, 7 A Output
Data Sheet
(ii) The temperature of the transformer does not
exceed 125°C, or
Characterization
General Information (iii) The nominal rating of the converter.
The converters have been characterized for many
operational aspects, to include thermal derating
(maximum load current as a function of ambient
temperature and airflow) for vertical and horizontal
mounting, efficiency, startup and shutdown
parameters, output ripple and noise, transient
response to load step-change, overload, and short
circuit.
During normal operation, derating curves with
maximum FET temperature less or equal to 125°C
should not be exceeded. Temperature at
thermocouple locations TC1 and TC2 shown in Fig. H
should not exceed 100°C and 125°C respectively, in
order to operate inside the derating curves.
Test Conditions
All data presented were taken with the converter
soldered to a test board, specifically a 0.060” thick
printed wiring board (PWB) with four layers. The top
and bottom layers were not metallized. The two inner
layers, comprised of two-ounce copper, were used to
provide traces for connectivity to the converter.
The lack of metallization on the outer layers as well
as the limited thermal connection ensured that heat
transfer from the converter to the PWB was
minimized. This provides a worst-case but consistent
scenario for thermal derating purposes.
Fig. H: Locations of the thermocouple for thermal testing.
Efficiency
Figure 2 shows the efficiency vs. load current plot for
ambient temperature of 25ºC, airflow rate of 300 LFM
(1.5 m/s) with vertical mounting and input voltages of
36V, 48V, 65V, and 75V. Also, a plot of efficiency vs.
load current, as a function of ambient temperature
with Vin=48V, airflow rate of 200 LFM (1 m/s) with
vertical mounting is shown in Figure 3.
All measurements requiring airflow were made in the
vertical and horizontal wind tunnel using Infrared (IR)
thermography and thermocouples for thermometry.
Ensuring components on the converter do not
exceed their ratings is important to maintaining high
reliability. If one anticipates operating the converter
at or close to the maximum loads specified in the
derating curves, it is prudent to check actual
operating temperatures in the application.
Thermographic imaging is preferable; if this
capability is not available, then thermocouples may
be used. The use of AWG #40 gauge thermocouples
is recommended to ensure measurement accuracy.
Careful routing of the thermocouple leads will further
minimize measurement error. Refer to Fig. H for the
recommended measuring thermocouple location.
Power Dissipation
Figure 4 shows the power dissipation vs. load current
plot for Ta = 25ºC, airflow rate of 300 LFM (1.5 m/s)
with vertical mounting and input voltages of 36V, 48V,
65V, and 75V. Also, a plot of power dissipation vs.
load current, as a function of ambient temperature
with Vin = 48V, airflow rate of 200 LFM (1 m/s) with
vertical mounting is shown in Figure 5.
Startup
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 Figure 6 and Figure 7,
respectively.
Thermal Derating
Load current vs. ambient temperature and airflow
rates are given in Figure 1. 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). Ripple and Noise
For each set of conditions, the maximum load current
was defined as the lowest of: Figure 10 shows the output voltage ripple waveform,
measured at full rated load current with a 10 µF
tantalum and 1µF ceramic capacitor across the output.
Note that all output voltage waveforms are measured
across a 1µF ceramic capacitor.
(i) The output current at which any FET junction
temperature does not exceed a maximum specified
temperature of 125°C as indicated by the
thermographic image, or The input reflected-ripple current waveforms are
obtained using the test setup shown in Figure 11.
ZD-02096 Rev. 1.0 www.power-one.com Page 8 of 12