Lucent Technologies Inc.
11
Data Sheet
May 2000
dc-dc Converters; 36 to 75 Vdc Input, 3.3 Vdc Output; 33 W to 50 W
QW050F1 and QW075F1 Power Modules:
Feature Descriptions
(continued)
Output Voltage Set-Point Adjustment
(Trim)
(continued)
8-715 (C).b
Figure 20. Circuit Configuration to Increase
Output Voltage
8-2580 (C)
Figure 21. Resistor Selection for Increased Output
Voltage
Output Overvoltage Protection
The output overvoltage protection consists of circuitry
that monitors the voltage on the output terminals. If the
voltage on the output terminals exceeds the overvolt-
age protection threshold, then the module will shut
down and latch off. The overvoltage latch is reset by
either cycling the input power for 1.0 second or by tog-
gling the on/off signal for 1.0 second.
Overtemperature Protection
These modules feature an overtemperature protection
circuit to safeguard against thermal damage. The circuit
shuts down and latches off the module when the maxi-
mum case temperature is exceeded. The module can
be restarted by cycling the dc input power for at least
1.0 second or by toggling the primary or secondary ref-
erenced remote on/off signal for at least 1.0 second.
Thermal Considerations
Introduction
The power modules operate in a variety of thermal
environments; however, sufficient cooling should be
provided to help ensure reliable operation of the unit.
Heat-dissipating components inside the unit are ther-
mally coupled to the case. Heat is removed by conduc-
tion, convection, and radiation to the surrounding
environment. Proper cooling can be verified by mea-
suring the case temperature. Peak temperature (T
occurs at the position indicated in Figure 22.
C
)
8-2104 (C)
Note: Top view, pin locations are for reference only.
Measurements shown in millimeters and (inches).
Figure 22. Case Temperature Measurement
Location
The temperature at this location should not exceed
100 °C. The output power of the module should not
exceed the rated power for the module as listed in the
Ordering Information table.
Although the maximum case temperature of the power
modules is 100 °C, you can limit this temperature to a
lower value for extremely high reliability.
V
I
(+)
V
I
(–)
ON/OFF
CASE
V
O
(+)
V
O
(–)
SENSE(+)
TRIM
SENSE(–)
R
adj-up
R
LOAD
2
4
6
8
10
10k
100k
1M
0
10M
A
)
% CHANGE IN OUTPUT VOLTAGE (
%)
14
(0.55)
V
I
(–)
ON/OFF
V
I
(+)
V
O
(–)
TRIM
V
O
(+)
(+)SENSE
(–)SENSE
33 (1.30)