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