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Application Notes
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(R1)
Adj Down
R2
(R3)
31.6k
(VR1), 5.1V
MM3Z5V1
+V
IN
–V
IN
PT4310
Vo
1
(+)
+Vin
-Vin
±Vo
Adjust
11
17
18
1
2
3
COM
Remote
On/Off
12
Vo
2
(–)
Note:
(R3)
and
(VR1)
are only
required with
(R1)
, for adjusting
the output down.
PT4310 Series
Adjusting the Output Voltage of the PT4310
Series of Isolated DC/DC Converters
The PT4310 is a series of 6-watt isolated dual-output
DC/DC converters. The PT4310 series is functionally
similar and pin-compatible with the former PT4300 series,
but the adjustment of the output voltages is different
1
.
The ±V
o
output voltages of the PT4310 series may be
adjusted higher or lower than the factory trimmed value.
The adjustment method uses a single external resistor to
adjust the magnitude of both output voltages by as much
as ±5%. When adjusting the output voltages to a lower
value, an external bias voltage, referenced to the –V
in
(primary), is also required.
2
Figure 1-1 gives a suggested schematic for the PT4310
output voltage adjustment. The components
(R
3
)
and
(VR
1
)
are only required with
(R
1
)
.
3
Adjust Up:
Add a resistor, R
2
, between V
o
Adjust (pin 12)
and –V
in
(pin 17).
Adjust Down:
An increase in the ±V
out
output voltages is
obtained by adding a resistor,
(R
1
)
, between V
o
Adjust
(pin 12) and a +5 VDC external voltage source. The
voltage source must be referenced to –V
in
(pin 17). A
simple external voltage source may be implemented by
adding the components
(R
3
)
and
(VR
1
)
in Figure 1-1.
Refer to Table 1-1 for the value of the external adjust
resistors, R
2
, or
(R
1
)
required to adjust each model of the
PT4310 series, up or down respectively by the stated
percentage. See Figure 1-1 for the placement of
(R
1
)
,
R
2
, and other components.
DC/DC CONVERTER ADJUSTMENT RESISTOR VALUES
Series Pt #
PT4311
V
o
(nom)
±5 V
(Io
1
+|Io
2
|)max
4
1.2 A
|±Vo|% Adjust
PT4313
±12 V
0.5 A
PT4314
±24 V
0.25 mA
–5.0%
–2.5%
0.0%
+2.5%
+5.0%
(90.9 k
)
(750 k
)
(0 k
)
(511 k
)
(220 k
)
(950 k
)
750 k
90.9 k
511 k
0 k
950 k
220 k
R1 =
(Blue)
R2 =Black
Figure 1-1
Table 1-1
Notes
1.
In most stand-alone applications the PT4310 series is a
direct substitute for the PT4300 series. However, the
method of output voltage adjustment differs between
the two series. For existing applications that use a
PT4300 part, a modification to the circuit will be
necessary if the output voltage is required to be
adjusted to a value other than the pre-trimmed factory
setting.
2. The adjustment control input, V
o
Adjust (pin 12) is
referenced to –V
in
(pin 17).
3.
(R
3
)
and
(VR
1
)
provide a +5 VDC external bias voltage
that is required for
(R
1
)
to adjust the output voltages
down. If the outputs are to be adjusted up, only the R
2
is required.
4. The PT4310 series is rated for 6 watts total output.
An increase in the output voltage will require a
corresponding reduction in the maximum allowed
total output current (Io
1
+
Io
2
) max in Table 1-1.
The total current from both outputs must comply
with the following equation:-
Io
1 +
Io
2
=
6
V
a
Adc
or (Io
1
+
Io
2
)max,
whichever is less.
Where,
V
a
= the new (adjusted) output voltage.