BLOCK DIAGRAM
INPUT
FILTER
1
OUTPUT
FILTER
5
CONTROLLER
2
9
ERROR
AMP
& REF
3
4
10
APPLICATION INFORMATION
InhibitFunction
DeviceSynchronization
Whenever multiple DC/DC converters are utilized in
a single system, significant low frequency noise
may be generated due to slight difference in the
switching frequencies of the converters (beat fre-
quencynoise). Becauseofthelowfrequencynature
of this noise (typically less than 10KHz), it is difficult
to filter out and may interfere with proper operation
of sensitive systems (communications, radar or
telemetry). Lambda Advanced Analog offers an option
whichprovidessynchronizationofmultipleAHE/ATW/
ATO type converters, thus eliminating this type of noise.
Connecting the inhibit input (Pin 2) to input common
(Pin 10) will cause the converter to shut down. It is
recommended that the inhibit pin be driven by an
open collector device capable of sinking at least
400µA of current. The open circuit voltage of the
inhibit input is 11.5 ±1VDC.
EMI Filter
An optional EMI filter (AFC461) will reduce the input
ripple current to levels below the limits imposed by
MIL-STD-461 CEO3.
To take advantage of this capability, the system
designer must assign one of the converters as the
master. Then, by definition, the remaining convert-
ers become slaves and will operate at the masters’
switching frequency. The user should be aware that
the synchronization system is fail-safe; that is, the
slaves will continue operating should the master
frequency be interrupted for any reason. The layout
must be such that the synchronization output (pin 9)
of the master device is connected to the synchroni-
zation input (pin 9) of each slave device. It is
advisable to keep this run short to minimize the
possibility of radiating the 250KHz switching fre-
quency.
Output Adjust (AHE2805) only
The output voltage of the AHE2805 can be adjusted
upward by connecting Output Adjust (Pin 3) and
Output Common (Pin 4) as shown in Table 1.
Resistance
Pin 3 to 4
Output Voltage
Increase %
×
0
390k
145k
63k
22k
0
+ 1%
+ 2%
+ 3%
+ 4%
+ 5%
The appropriate parts must be ordered to utilize this
feature. After selecting the converters required for
the system, an ‘MSTR’ suffix is added for the master
converter part number and an ‘SLV’ suffix is added
for slave part number. See Part Number section.
Table 1 Output adjustment resistor values
5