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IMX 7-Family
DC-DC Converters <40 W
Rugged Environment
6 - 26
Edition 2/96 - Melcher AG
MELCHER
The Power Partners.
6.1
a) Adjustment by means of an external resistor.
Programming of the output voltage by means of an exter-
nal resistor
Rext is possible within a limited range of
100...105 % of
Uo nom. Rext should be connected between
the R-pin and Vi–. Connection of
Rext to Vi+ may damage
the converter. Following table indicates suitable resistor
values for typical output voltages under nominal
conditions (
Ui nom, Io = 0.5 Io nom), with either paralleled
outputs or equal load conditions on each output.
Table 11: Rext for Uo > Uo nom;
approximate values (Ui nom, Io1, 2 = 0.5 Io1/2 nom)
Uo nom
2
× 5 V
2
× 12/15/24 V
Uo [% Uo nom]
Rext [k
]
Rext [k
]
105...108 (107 typically)
0
105
18
1.5
104
43
5.6
103
86
12.6
102
175
26
101
470
68
100
∞∞
b) Adjustment by means of an external voltage source
Uext.
For external output voltage programming in the range
75...105 % of
Uo nom a (0...20 V) source Uext is required,
connected to the R-pin and Vi–.The table below indicates
typical
Uo versus Uext values under nominal conditions
(
Ui nom, Io = 0.5 Io nom), with either paralleled outputs or
equal load conditions on each output. Applying a control
voltage greater than 20 V will set the converter into a hic-
cup mode. Direct paralleling of the R-pins of units con-
nected in parallel is feasible.
Table 12: Uext for Uo = 75...105% Uo nom;
typical values (Ui nom, Io1, 2 = 0.5 Io1/2 nom)
Uo nom
2
× 5 V
2
× 12 V
2
× 15 V
2
× 24 V
Uo [% Uo nom]
Uext [V]
105
0.5
0.07
0.37
0.25
102
1.68
1.43
1.64
1.60
95
4.60
85
8.74
9.22
8.92
9.23
75
12.84
13.64
13.28
13.75
11.0
11.5
12.0
12.5
13.0
13.5
Uo1 [V]
0.03
0.10
0.15
0.20
0.25
0.30
0.35 Io1 [A]
0.05
Io2 = (0.1...1) Io nom
Fig. 13
Uo1 versus Io1 (typ) for various Io2
Fig. 11
Uo versus Io (typ) of single output units with Uo = 5.1 V.
Fig. 12
Uo versus Io (typ) of double output units, with both outputs
in parallel.
7
8
9
10
11
12
13
Uo [V]
0.1
0.2
0.3 0.4
0.5
0.6
0.7
0.8 0.9
Io total [A]
0
5.5
5.0
4.5
4.0
3.5
3.0
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Io [A]
Uo [V]
Output Voltage Regulation
Output voltage regulation of single output units:
Output voltage regulation of double output units (2
× 12 V)
with output 1 and 2 connected in parallel:
Load regulation of double output units (2 x 12 V) with out-
puts independently loaded. Cross load effect is negligible.