Q24S25018-NS00
| Model | Q24S25018-NS00 |
| Description | DC-DC Regulated Power Supply Module, 1 Output, Hybrid, |
| PDF file | Total 14 pages (File size: 253K) |
| Chip Manufacturer | BEL |
Q24S25018 DC-DC Converter Data Sheet
18-36 VDC Input; 1.5 VDC @ 25A Output
Characterization
General Information
The converter has 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, start-up and shutdown
parameters, output ripple and noise, transient response to
load step-change, overload and short circuit.
The following pages contain specific plots or waveforms
associated with the converter. Additional comments for
specific data are provided below.
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
metalized. The two inner layers, comprising two-ounce
copper, were used to provide traces for connectivity to the
converter.
The lack of metalization 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.
All measurements requiring airflow were made in
Power-One’s vertical and horizontal wind tunnel facilities
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. Power-One
recommends the use of AWG #40 gauge thermocouples to
ensure measurement accuracy. Careful routing of the
thermocouple leads will further minimize measurement error.
Refer to Figure 28 for optimum measuring thermocouple
location.
Thermal Derating
Load current vs. ambient temperature and airflow rates are
given in Figs. 10-13. 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), and vertical and horizontal converter
mounting.
For each set of conditions, the maximum load current was
defined as the lowest of:
(i) The output current at which either any FET junction
temperature did not exceed a maximum specified
temperature (either 105 °C or 120 °C) as indicated by the
thermographic image, or
(ii) The nominal rating of the converter (25 A)
During normal operation, derating curves with maximum FET
temperature less than or equal to 120 °C should not be
exceeded. Temperature on the PCB at the thermocouple
location shown in Fig. 28 should not exceed 118 °C in order
to operate inside the derating curves.
Efficiency
Efficiency vs. load current plots are shown in Figs. 14 and 16
for ambient temperature of 25 ºC, airflow rate of 300 LFM
(1.5 m/s), both vertical and horizontal orientations, and input
voltages of 18 V, 27 V and 36 V. Also, plots of efficiency vs.
load current, as a function of ambient temperature with Vin =
27 V, airflow rate of 200 LFM (1 m/s) are shown for both a
vertically and horizontally mounted converter in Figs. 15 and
17, respectively.
Start-up
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 10,000
F
load capacitance in
Figs. 18 and 19, respectively.
Ripple and Noise
Figure 22 shows the output voltage ripple waveform, meas-
ured 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
F
ceramic
capacitor.
The input reflected ripple current waveforms are obtained
using the test setup shown in Fig 23. The corresponding
waveforms are shown in Figs. 24 and 25.
MDC10152 Rev.1.0, 6-Apr-10
Page 8 of 14
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