ADDC02812DAKV View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
ADDC02812DAKV Datasheet PDF : 20 Pages
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ADDC02812DA/ADDC02815DA
1.2
1.1
1.0
0.9
The thermal shutdown feature has been set to shut down the
converter when the case temperature is nominally 110°C to
115°C. To raise the temperature at which shutdown occurs,
connect a resistor with the value shown in Figure 24 from Pin 9
to the input return (Pin 10). To completely disable the tem-
perature shutdown feature, connect a 50 kΩ resistor from Pin 9
to the input return (Pin 10).
1400
0.8
1200
1000
0.7
0.5
1.0
1.5
2.0
OBSOLETE VIL – V
Figure 23. Input Characteristics of Pin 6 When Pulled Low
Pin 7 (SYNC)
Pin 7 can be used for connecting multiple converters to a master
clock. This master clock can be either an externally user-supplied
clock or it can be a converter that has been modified and desig-
nated as a master unit. Consult factory for availability of these
devices. Capacitive coupling of the clock signal will insure that
if the master clock stops working the individual units will con-
tinue to operate at their own internal clock frequency, thereby
eliminating a potential single point failure. Capacitive coupling
will also permit a wider duty cycle to be used. Consult factory
for more information. The SYNC pin has an internal pull-down
so it is not necessary to sink any current when driving the pin
low.
800
600
400
200
0
120
125
130
135
140
145
150
CASE TEMPERATURE – °C
Figure 24. External Resistor Value for Raising Tempera-
ture Shutdown Point
INPUT VOLTAGE RANGE
The steady state operating input voltage range for the converter
is defined as 18 V to 40 V. The abnormal operating input volt-
age range is defined as 16 V to 50 V. In accordance with MIL-
For user-supplied master clocks with no external circuitry, the
STD-704D, the converter can operate up to 50 V dc input for
following specifications must be met:
transient conditions as long as 50 milliseconds, and it can oper-
a. Frequency: 1.00 MHz min
ate down to 16 V dc input for continuous operation during
b. Duty cycle: 7% min, 14% max
emergency conditions. Figure 4 (typical low line dropout vs.
c. High state voltage high level: 4 V min to 7 V max
load) shows that the converter can work continuously down to
d. Low state voltage low level: 0 V min to 3.0 V max
and below 16 V dc under reduced load conditions.
Users should note that the SYNC pin is referenced to the input
return of the converter. If the user-supplied master clock is gen-
erated on the output side of the converter, the signal should be
isolated.
The ADDC02812DA and ADDC02815DA can be modified to
survive, but not work through, the upper limit input voltages
defined in MIL-STD-704A (aircraft) and MIL-STD-1275A
(military vehicles). MIL-STD-704A defines an 80 V surge
Users should be careful about the frequency selected for the
external master clock. Higher switching frequencies will reduce
efficiency and may reduce the amount of output power available at
minimum input line. Consult factory for modified standard switch-
ing frequency to accommodate system clock characteristics.
Pin 8 (ISHARE)
Pin 8 allows paralleled converters to share the total load cur-
rent, typically within ± 5% at full load. To use the current share
feature, connect all current share pins to each other and con-
nect the SENSE pins on each of the converters. The current
sharing function is sensitive to the differential voltage between
the input return pins of paralleled converters. The current shar-
ing function is also sensitive to noise, and care should be taken
that lasts for 1 second before it falls below 50 V, while MIL-
STD-1275A defines a 100 V surge that lasts for 200 milliseconds
before it falls below 50 V. In both cases, the ADDC02812DA
and ADDC02815DA can be modified to operate to specifica-
tion up to the 50 V input voltage limit and to shut down and
protect itself during the time the input voltage exceeds 50 V.
When the input voltage falls below 50 V as the surge ends, the
converter will automatically initiate a soft start. In order to sur-
vive these higher input voltage surges, the modified converter
will no longer have input transient protection, however, as de-
scribed below.
Contact the factory for information on units surviving high
input voltage surges.
in the routing of connections.
Input Voltage Transient Protection: The converters have a
Pin 9 (TEMP)
Pin 9 can be used to indicate case temperature or to raise or
disable the temperature at which thermal shutdown occurs.
Typically, 3.90 V corresponds to +25°C, with a +13.1 mV/°C
change for every 1°C rise. The sensor IC (connected from Pin
9 to the input return (Pin 10)) has a 13.1 kΩ impedance.
transient voltage suppressor connected across their input leads
to protect the units against high voltage pulses (both positive
and negative) of short duration. With the power supply con-
nected in the typical system setup shown in Figure 17, a tran-
sient voltage pulse is created across the converter in the
following manner. A 20 µF capacitor is first charged to 400 V.
–10–
REV. 0
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