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70IMX35D05D15-8 Datasheet, PDF (9/15 Pages) Power-One – IMX35 Series Data Sheet 35 Watt Quad-Output DC-DC Converters | |||
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IMX35 Series Data Sheet
35 Watt Quad-Output DC-DC Converters
®
Auxiliary Functions
Adjustable Output Voltage
As a standard feature, the IMX35 offer adjustable output
voltages in the range of 85 to 105% of Vo nom. Fig. 12 shows the
schematic diagram for the adjustment of quad-output models.
All models with equal output voltages have a Trim input at pin
5 referenced to the primary side, influencing all outputs simul-
taneously. Models with different output voltages exhibit a
Trim1 input, influencing only the first power train (Vo1 and Vo4).
Adjustment by means of an external resistor Rext:
+
Vext
â
Vi+
4
Trim
5
Rext
Viâ 2
06137c
Vo1+
16
Vo1â
15
Control
circuit
Vref = 2.5 V
Vo2+
13
Vo2â
14
Fig. 13
Output voltage control by means of the Trim input
Adjustment of the output voltage by means of an external
resistor Rext is possible within the range of 100 to 105% of
Vo nom. Rext should be connected between Trim (pin 5) and Viâ
(pin 2). The following table indicates suitable resistor values for
typical output voltages under nominal conditions (Vi nom, Io =
0.5 Io nom).
Note: Connection of Rext to Vi+ may damage the converter.
Adjustment by means of an external voltage source Vext
Table 7: Rext for Vo > Vo nom;
approximate values (Vi nom, Io = 0.5 Io nom)
Vo [% Vo nom]
Rext [kâ¦]
Trim
Trim1
105 to 108 (107 typically)
0
0
105
10
17
102
62
110
100
â
â
Table 8: Vo versus Vext for Vo = 85 to 105% Vo nom;
typical values (Vi nom, Io = 0.5 Io nom)
Vo [% Vo nom]
>105
102
100
95
90
85
Vext [V]
Trim [V]
Trim1 [V]
0
0
1.8
1.5
2.5
2.5
4.3
4.25
6.2
6.2
8
8
Synchronization (W)
It is possible to synchronize the switching frequency of one or
more converters to an external clock signal.
This logic input W can be used to synchronize the oscillator to
an external frequency source. This signal is edge-triggered
with TTL thresholds and requires a source frequency of 490 to
540 kHz (duty cycle 10 to 90%). The external source frequency
is internally divided by 2 to define the switching frequency of
the converter. If unused, this pin can be connected to V1â (pin
2) or left open-circuit.
Reference Output (Ref)
The converter provides a stable 5 V (±0.1 V) reference signal
on pin 7 (Ref). The output is protected by a 1 k⦠resistor. The
signal may be used also in conjunction with the Trim input (pin
5) as a limited external voltage reference.
It is recommended to connect a filter capacitor (0 .1 µF)
between Ref and Viâ, if Ref is used.
Shutdown
The outputs of the converters may be enabled or disabled by
means of a logic signal (TTL, CMOS, etc.) applied to shut-
down (pin 8). If the shutdown function is not required, pin 8
should be left open-circuit:
Converter operating:
Converter disabled:
2.0 to 20 V
â10 to 0 .7 V
For external output voltage adjustment in the range 85 to
105% of Vo nom a voltage source Vext (0 to 20 V) is required,
connected to Trim or Trim1 (pin 5) and Viâ. The table below
indicates typical values Vo versus Vext. Applying a control
voltage of 15 to 20 V will set the converter into the hiccup
mode. Direct paralleling of the Trim pins of converters of the
same type connected in parallel is feasible.
BCD20009-G Rev AC, 06-May-2013
Page 9 of 15
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