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IMX4 Series Data Sheet

4 Watt DC-DC Converters

BCD20006-G Rev AC, 06-Jul-2012

Page 5 of 12

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Input Transient Voltage Protection

In many applications transient voltages on the converter input

are always possible. These may be caused for example by

short circuits between Vi+ and Vi–, where the network

inductance may generate high energy pulses.

In order to protect the converter, a transient voltage

suppressor diode is fitted to the input; see table below.

Table 4: Built-in transient voltage suppressor

Model

Breakdown

Peak power

Peak pulse

voltage

at 1 ms

current

5IMX4

--

--

--

20IMX4

40 V

600 W

10.3 A

40IMX4

100 V

600 W

4.1 A

70IMX4

150 V

600 W

2.9 A

Fig. 8

External circuitry to comply with

IEC/EN 61000-4-5, level 2.

Vi+

Vi–

D

+

04036b

If transients generating currents above the peak pulse current

shown in figure 8 is recommended. It provides compliance with

transients according to IEC/EN 61000-4-5, level 2. The comp-

onents are specified in table 5.

If 40IMX4 converters should withstand 150 V transients

according to 19Pfl1, the same external circuitry with similar

components as shown in figure 8 can be used.

Fuse and Reverse Polarity Protection

The suppressor diode on the input also protects against

reverse polarity input voltage. An external fast fuse is required

to limit this reverse current; see table below.

Table 6: External input fuse

Model

Fuse type

5IMX4

Fast 1.6 A

20IMX4

Fast 1 A

40IMX4

Fast 0.5 A

70IMX4

Fast 0.315 A

Table 5: Components for the circuitry fig. 8

Model

20IMX4

40IMX4

70IMX4

330 µH, 0.42 W

330 µH, 0.42 W

330 µH, 0.65 W

1 A

0.6 A

0.3 A

68 µF, 50 V

68 µF, 100 V

100 µF, 200 V

D

ON 1.5KE 39 A

ON 1.5KE 82 A

–