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BCD20009-G Rev F, 20-Nov-2020

Page 10 of 16

IMX35 Series

35 Watt Quad-Output DC-DC Converter

© 2020 Bel Power Solutions & Protection

Auxiliary Functions

Adjustable Output Voltage

As a standard feature, the IMX35 offer adjustable output voltages in the range of 85 to 105% of V

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 simultaneously.

Models with different output voltages exhibit a Trim1 input, influencing only the first power train (V

Adjustment by means of an external resistor R

Trim

Vo1+

Vo2–

+

–

Vi+

Vi–

Vo1–

Vo2+

06137c

Control

circuit

4

5

2

16

15

13

14

Fig. 13

Output voltage control by means of the Trim input

Table 7: R

approximate values (V

V

R

Trim

Trim 1

105 to 108 (107 typically)

105

102

100

0

10

62

∞

0

17

110

∞

Table 8: V

typical values (V

V

V

Trim

[V]

Trim 1

[V]

> 105

102

100

95

90

85

0

1.8

2.5

4.3

6.2

8

0

1.5

2.5

4.25

6.2

8

Adjustment of the output voltage by means of an external resistor R

should be connected between Trim (pin 5) and Vi– (pin 2). The following table indicates suitable resistor values for typical output

voltages under nominal conditions (V

Note: Connection of R

Adjustment by means of an external voltage source V

ext

For external output voltage adjustment in the range 85 to 105% of V

Trim or Trim1 (pin 5) and Vi–. The table below indicates typical values V

set the converter into the hiccup mode. Direct paralleling of the Trim pins of converters of the same type connected in parallel is

feasible.

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 V1– (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 kΩ 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 Vi–, if Ref is used.