24IMS15 データシートの表示（PDF） - Bel Fuse Inc.

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24IMS15

15 Watt DC-DC Converters

Bel Fuse Inc. 

IMX15, IMY15, IMS15 Series Data Sheet

15 Watt DC-DC Converters

Auxiliary Functions

Shutdown Function

The outputs of the converters may be enabled or disabled by

means of a logic signal (TTL, CMOS, etc.) applied to the shut-

down pin. If this function is not required, the shut-down pin

should be left open-circuit.

• Converter operating:

2.0 to 20 V

• Converter disabled:

–10 to +0.7 V

Adjustable Output Voltage

• R input for single-output models and -0503-models

• Trim input for double-output models

As a standard feature, the single- and double-output models

offer adjustable output voltage(s) by using the control input R or

Trim. If the control input is left open-circuit, the output voltage is

set to Vo nom. For output voltages Vo > Vo nom, the minimum input

voltage Vi min (see Electrical Input Data) increases

proportionally to Vo/Vo nom.

Single-output models with synchronous rectifier (G):

The R input is referenced to the secondary side of the

converter. Adjustment of the output voltage is possible by

means of an external resistor connected between the R pin and

either Vo+ or Vo–.

Note: For models with synchronous rectifier the logic for Vo

adjustment differs from other models with R input.

06131

Vi+

Vo+

Rext1

R

a) Adjustment by means of an external resistor Rext.

Depending upon the value of the required output voltage,

the resistor shall be connected:

either: Between the R pin and Vo– to achieve an output

voltage adjustment range of Vo ≈ 80 to 100 % of Vo nom.

Rext1 ≈ 4 kΩ • –V–o–n–Vo–mo––––V–o

or: Between the R pin and Vo+ to achieve an output voltage

range of Vo ≈ 100 to 105 % of Vo nom.

Rext2 ≈ 4 kΩ • –2–.–5–(VV––o•––(V–2–o./–5V–Vo–)n–o–m––––1–)

b) Adjustment by means of an external voltage Vext

between Vo– and R pin.

The control voltage range is 1.96 to 2.62 V and allows for

adjustment in the range of Vo ≈ 80 to 105% of Vo nom.

Vext ≈ –V–oV–•–o2–n.o–5m–V–

Attempting to adjust the output below this range will cause

the converter to shut down (hiccup mode).

Note: Applying an external control voltage >2.75 V may damage

the converter.

06029e

Vi+

Vo+

Vref = 2.5 V 4 kΩ

+

Control

logic

Vi–

Rext 2

R

+

Rext1

Vext

Vo–

–

Rext2

Vi–

Vo–

Fig. 14

Output voltage control for single-output models with

synchronous rectifier.

Table 8: Vo versus Vext approximate values

Vo nom

[V]

3.3

Typ. values of Rext1

Vo [% of Vo nom] Rext1 [kΩ]

90

0.47

95

2.7

100

∞

Typ. values of Rext2

Vo [% of Vo nom] Rext2 [kΩ]

100

∞

105

15

110

6.8

5.1

90

3.3

95

8.2

100

∞

100

∞

105

9.1

110

3.9

Fig. 15

Output voltage control for single-output models, -0503-models,

and double-output models by means of the R input.

Double-output models with Trim input:

The Trim input is referenced to the primary side. The figure

below shows the topology. Adjustment is possible trough either

an external resistor or an external voltage source Vext.

06089a

Vi+

Vo1+

+

Vext

–

Trim

Rext

Vi–

Control

circuit

Vref 2.5 V

Vo1–

Vo2+

Vo2–

All other models fitted with R-input:

The R input is referenced to the secondary side of the

converter. Adjustment of the output voltage is possible by

means of either an external resistor or a voltage source.

Fig. 16

Output voltage control for double-output models (with Trim

input) by means of the Trim input.

BCD20008-G Rev AE, 25-Aug-2017

MELCHER

The Power Partners.

Page 13 of 19

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