AUG 13, 2002
Rev 1.0
Page 9 of 15
www.power-one.com
IMX35 Series: 35W DC-DC Converters
Product Specifications
9-36V, 18-75V, 40-121V & 60-150V Inputs
Aug 2002
Dual/Triple/Quad Outputs 3.3V, 5V, 12V & 15V
Auxiliary Functions
Adjustable Output Voltage
As a standard feature, the IMX 35 offer adjustable output
voltages in the range 90...105% of Vo nom by use of a con-
trol pin. The Trim control is offered either on primary or sec-
ondary side of the converter depending on type.
Vo1+
Vi+
Vi–
Vo1–
06136
Trim1
R
ext1
R
ext2
4
2
17
18
15
Fig. 14
Output voltage control for the Trim1 input referenced to
the secondary side.
Table 7: Vo1 versus Rext for Vo1 = 90...105% Vo nom; typical
values (Vi nom, Io1/2 = 0.5 Io1/2 nom)
Vo nom
Rext1
Rext2
[V]
Vo1 [V]
[k
]
Vo1 [V]
[k
]
3.3
2.97
1.8
3.3
3.135
4.7
3.47
11
3.673
5
5.1
4.59
2.2
5.1
4.84
9.1
5.25
8.5
5.0
33
5.35
3
Adjustment by means of an external resistor Rext:
Adjustment of the output voltage by means of an exter-
nal resistor Rext is possible within the range of
100...105% of Vo nom. Rext should be connected between
Trim (pin 5) and Vi– (pin 2). Connection of Rext to Vi+
may damage the converter. The following table indicates
suitable resistor values for typical output voltages under
nominal conditions (Vi nom, Io = 0.5 Io nom).
Adjustment by means of an external voltage source Vext
For external output voltage adjustment in the range
85...105% of Vo nom a (0...20 V) source Vext is required,
connected to the Trim (pin 5) and Vi–. The table below in-
dicates typical Vo versus Vext values. Applying a control
voltage 15...20 V will set the converter into a hiccup
mode. Direct paralleling of the Trim pins of units of the
same type connected in parallel is feasible.
Table 9: Vo versus Vext for Vo = 85...105% Vo nom;
typical values (Vi nom, Io = 0.5 Io nom)
Uo [% Uo nom]
Uext [V]
Trim [V]
Trim 1/4 [V]
>105
0
102
1.8
1.5
100
2.5
95
4.3
4.25
90
6.2
85
8
Table 8: Rext1 for Vo > Vo nom;
approximate values (Vi nom, Io = 0.5 Io nom)
Vo [% Vo nom]
Rext [k
]
Trim [k
]
Trim 1/4 [k
]
105...108 (107 typically)
0
105
10
17
102
62
110
100
The quadruple output units are shown in block diagram (fig.
2). All types with equal output voltage have the Trim func-
tion connected to pin 5 referenced to the primary side
which influences all outputs simultaneously. The schemat-
ics are shown in fig. 15, the values of the adjust resistor Rext
in Table 8 and the external voltage source in Table 9.
Trim
Vo1+
Vo2–
+
U
ext
–
Vi+
Vi–
R
ext
Vo1–
Vo2+
06137
Control
circuit
Uref = 2.5 V
4
5
2
17
15
13
11
Fig. 15
Output voltage control for Quad (double) output units by
means of the Trim input on the primary side.
Block diagram (fig. 1) shows the triple output units. They of-
fer a Trim1 input (pin 18) on the secondary side to adjust
Vo1. The other outputs remain unchanged.
The IMX 35 triple output feature a main power train with
magnetic feedback and synchronous rectifier. The simpli-
fied circuit is shown in Fig. 14.
The Trim1 (pin 18) is secondary referenced and influences
only the main power train. Adjustment of the output voltage
is possible by means of an external resistor Rext between
the Trim1 pin and either Vo1+ or Vo1–. If the control input
is left open circuit, the output voltage is set to Vo1 nom.
Table 7 lists typical values required to program the output
voltage to approximately the values of Vo1 indicated.
Triple output adjustment
Quad output adjustment