AHP2700S_15 Datasheet, PDF (8/12 Pages) International Rectifier – HYBRID - HIGH RELIABILITY DC/DC CONVERTER

AHP270XXS Series
Input Filter
The AHP270XXS series converters incorporate a single
stage LC input filter whose elements dominate the input
load impedance characteristic during the turn-on sequence.
The input circuit is as shown in Figure IV.
For (V_NOM + 0.25V) < V_OUT < (V_NOM + 0.5V), a resistor is
connected between the +Sense and –Sense pins with
the –Sense connected to the output return as shown in
Figure V. The resistor value (R_ADJ) is calculated as
follows:
Figure IV. Input Filter Circuit
Pin 1
Pin 2
8.4µH
0.54µfd
R _ADJ
=
1000
⋅
⎡
⎢⎣_VOUT
V _NOM
− V_NOM
⎤
−
0.25
⎥
⎦
For V_NOM < V_OUT < (V_NOM + 0.25V), a resistor is connected
between the +Sense and +Output pins with the –Sense
connected to the output return as shown in Figure VI.
The resistor value (R_ADJ) is calculated as follows:
Input Overvoltage Protection
One additional protection feature is incorporated into the
AHP input circuit is input over-voltage protection. The
converter will shutdown at approximately 110% of the
maximum rated input voltage and restart once the input
voltage drops back below this threshold.
Undervoltage Lockout
A minimum voltage is required at the input of the converter
to initiate operation. This voltage is set to 150V ± 5V. To
preclude the possibility of noise or other variations at the
input falsely initiating and halting converter operation, a
hysteresis of approximately 10V is incorporated in this circuit.
Thus if the input voltage droops to 140V ± 5V, the converter
will shut down and remain inoperative until the input voltage
returns to ≈ 150V.
R _ADJ
=
1000
⎜⎜⎝⎛
0.25
V_OUT − V
NOM
− 1_{⎟⎟⎠⎞}
V_NOM = device nominal output voltage
V_OUT = desired output voltage
R_ADJ = value of the external resistor required to
achieve the desired Vout
Finding a resistor value for a particular output voltage, is
simply a matter of substituting the desired output voltage
and the nominal device voltage into the equation and solving
for the corresponding resistor value.
Output Voltage Adjust
In addition to permitting close voltage regulation of remotely
located loads, it is possible to utilize the converter sense
pins to incrementally increase the output voltage over a
limited range. The adjustments made possible by this
method are intended as a means to “trim” the output to a
voltage setting for some particular application, but are not
intended to create an adjustable output converter. These
output voltage setting variations are obtained by connecting
an appropriate resistor value in the locations as shown in
Figure V or Figure VI depending on the desired output
voltage. The range of adjustment and corresponding range
of resistance values can be determined by use of the
equations presented below.
Figure V. Connection for V > V + 0.25V
OUT
NOM
AHP270XXS
Enable 2
Share
+Sense
- Sense
Return
+Vout
R_ADJ
To Load
8
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