A Series
1 5 - 2 0 W , D U A L O U T P U T D C / D C C O N V E R T E R S
5
6
5
+OUTPUT
COMMON
–OUTPUT
+OUTPUT
+
+
1
6
8
1
2
+INPUT
–INPUT
COMMON
TRIM
COUT
+INPUT
–INPUT
LOAD
LOAD
+
CIN
20k
5-10
Turns
2
COUT
7
7
–OUTPUT
Figure ꢀ. Using External Capacitors to Reduce
Input/Output Ripple/Noise
Figure 3a.Trim Connections Using a Trimpot
Input Fusing
Certain applications and/or safety agencies may require the installation of
fuses at the inputs of power conversion components. For C&D A-Series
BWR ꢀ±-25 Watt DC/DC Converters, you should use slow-blow type fuses
with values no greater than the following:
5
+OUTPUT
1
+INPUT
LOAD
LOAD
8
6
VIN Range
Fuse Value
TRIM
COMMON
–OUTPUT
2
D±A
6A
4A
2A
–INPUT
Dꢀ2A
D48A
7
On/Off Control
The On/Off Control pin (pin 4) may be used for remote on/off operation. A
TTL logic high (+2 to +± Volts, 2±5µA max.) applied to pin 4 disables the
converter. A TTL logic low (5 to +5.8 Volts, 75µA max.), or no connection,
enables the converter. Control voltages should be referenced to pin 2
(–Input). Applying a voltage to the Control pin when no input power is applied
to the converter can cause permanent damage to the converter.
Figure 3b. Fixed-Value Trim Down Resistor
5
Synchronization
+OUTPUT
In critical applications employing multiple switching DC/DC converters, it may
be desirable to intentionally synchronize the switching of selected converters
(so the system noise can be reduced with notch filtering) or to purposely
desynchronize the converters (to lessen the current-carrying requirements on
intermediate dc buses). For multiple A-Series Converters, an external clock
can be applied to pin 4 (Control) of each device. It should be a square wave
with a maximum ꢀµsec "high" duration and an amplitude between +2V and
+±V (see On/Off Control) referenced to pin 2 (–Input). The frequency of the
synchronizing clock should be higher than that of any individual converter.
Therefore, it should be ꢀ8±kHz ±±kHz.
1
2
6
COMMON
TRIM
+INPUT
–INPUT
LOAD
LOAD
8
7
–OUTPUT
Figure 3c. Fixed-Value Trim Up Resistor
Output Trimming
The total output voltage span, from +Output (pin ±) to –Output (pin 7) may
be trimmed ±±ꢁ via a single external trimpot or fixed resistor. The trimpot
should be connected as shown in Figure 3a with its wiper connected to pin 8
(Trim). A trimpot can be used to determine the value of a single fixed resistor
which should be connected as shown in Figures 3b and 3c. Connect the
resistor between pin 8 (Trim) and pin ± (+Output) to trim "down" the output
voltages. Connect the resistor between pins 8 and 7 (–Output) to trim "up"
the output voltages. Fixed resistors should be metal-film types with absolute
TCR’s less than ꢀ55ppm/°C to ensure stability.
.
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