A
20 Watt HP Triple Series DC/DC Converters
2401 Stanwell Drive Concord, California 94520 Ph: 925/687-4411 or 800/542-3355 Fax: 925/687-3333 www.calex.com Email: sales@calex.com
6
3/2001
Case Grounding
The copper case serves not only as a heat sink but also as a
EMI shield. The 0.017 inch thick case provides >25 dB of
absorption loss to both electric and magnetic fields at 220
kHz, while at the same time providing 20 to 40 % better heat
sinking over competitive thin steel, aluminum or plastic designs.
The case shield is tied to the -input pin. This connection is
shown on the block diagram. The case is floating from the
output sections. The input is coupled to the outputs only by the
low 400 pF of isolation capacitance. This low I/O capacitance
insures that any AC common mode noise on the inputs is not
coupled to your output circuits.
Compare this isolation to the more usual 1000 - 2000 pF
found on competitive designs and you will see that CALEX
provides the very best DC and AC isolation available. After all,
you are buying an isolated DC/DC to cut ground loops. Don’t
let the isolation capacitance add them back in.
Temperature Derating
The HP Triple series can operate up to 90°C case temperature
without derating. Case temperature may be roughly calculated
from ambient by knowing that the HP Triples case temperature
rise is approximately 9.5°C per package watt dissipated.
For example: If a 24T HP converter is outputting 15 watts,
at what ambient could it expect to run with no moving air and
no extra heatsinking?
Efficiency of a 24T is approximately 84% at 15 watts of
output power, this leads to an input power of about 18 watts.
The case temperature rise would be 18 - 15 watts or 3 watts
× 9.5 = 29°C. This number is subtracted from the maximum
case temperature of 90°C to get: 61°C.
This example calculation is for an HP triple without any
extra heat sinking or appreciable air flow. Both of these factors
can greatly affect the maximum ambient temperature (see
below). Exact efficiency depends on input line and load
conditions, check the efficiency curves for exact information.
This is a rough approximation to the maximum ambient
temperature. Because of the difficulty of defining ambient
temperature and the possibility that the loads dissipation may
actually increase the local ambient temperature significantly,
these calculations should be verified by actual measurement
before committing to a production design.
Remember, it is the users responsibility to be sure that the
case temperature of the HP Triple does not exceed 90°C for
maximum reliability in operation.
Typical Performance (Tc=25°C, Vin=Nom VDC, Rated Load).
02
46
8
10
12
14
16
18
LINE INPUT (VOLTS)
0.0
0.7
1.4
2.1
2.8
3.5
INPUT
CURRENT
(AMPS)
12 VOLT INPUT CURRENT Vs. LINE INPUT VOLTAGE
100% LOAD
50% LOAD
0
1020
30405060
7080
LINE INPUT (VOLTS)
0.0
0.2
0.4
0.6
0.8
1.0
INPUT
CURRENT
(AMPS)
48 VOLT INPUT CURRENT Vs. LINE INPUT VOLTAGE
100% LOAD
50% LOAD
0
1020
3040
50
6070
8090
100
LOAD (%)
65
70
75
80
85
90
EFFICIENCY
(%)
12 VOLT EFFICIENCY Vs. LOAD
LINE = 9VDC
LINE = 12VDC
LINE = 18VDC
0
1020
3040
50
6070
8090
100
LOAD (%)
65
70
75
80
85
90
EFFICIENCY
(%)
48 VOLT EFFICIENCY Vs. LOAD
LINE = 36VDC
LINE = 48VDC
LINE = 72VDC
9
1011
1213
1415
1617
18
LINE INPUT(VOLTS)
65
70
75
80
85
EFFICIENCY(%)
12 VOLT EFFICIENCY Vs. LINE INPUT VOLTAGE
100% FULL LOAD
50% FULL LOAD
36
40
44
48
52
56
60
64
68
72
LINE INPUT(VOLTS)
60
65
70
75
80
85
90
EFFICIENCY(%)
48 VOLT EFFICIENCY Vs. LINE INPUT VOLTAGE
100% FULL LOAD
50% FULL LOAD
0
4
8
1216
2024
2832
36
LINE INPUT (VOLTS)
0.0
0.5
1.0
1.5
2.0
INPUT
CURRENT
(AMPS)
24 VOLT INPUT CURRENT Vs. LINE INPUT VOLTAGE
100% LOAD
50% LOAD
18
20
22
24
26
28
30
32
34
36
LINE INPUT(VOLTS)
70
75
80
85
90
EFFICIENCY(%)
24 VOLT EFFICIENCY Vs. LINE INPUT VOLTAGE
100% FULL LOAD
50% FULL LOAD
0
1020
3040
50
6070
8090
100
LOAD (%)
65
70
75
80
85
90
EFFICIENCY
(%)
24 VOLT EFFICIENCY Vs. LOAD
LINE = 18VDC
LINE = 24VDC
LINE = 36VDC