Triple Output, High-Efﬁciency, Smaller-Package, 25-40 Watt, DC/DC Converters
On/Off Control (Standard)
The On/Off Control pin (pin 5) may be used for remote on/off operation. As
shown in Figure 6, the control pin has an internal 10kΩ pull-up resistor to
approximately 10V. The converter is designed so that it is enabled when the
control pin is left open (normal mode) and disabled when the control pin is
pulled low (to less than +0.8V relative to –Input, pin 2).
Dynamic control of the on/off function is best accomplished with a mechani-
cal relay or an open-collector/open-drain drive circuit (optically isolated if
appropriate). The drive circuit should obviously be able to sink approximately
1mA when activated and withstand more than 10 Volts when deactivated.
Applying an external voltage to pin 5 when no input power is applied to the
converter can cause permanent damage to the converter. The on/off control
function, however, is designed such that the converter can be disabled (pin
5 pulled low) while input power is ramping up and then "released" once the
input has stabilized. Under these circumstances, it takes approximately 30ms
for the output of the fully loaded DC/DC to ramp up and settle to within ±1%
of its ﬁnal value after the converter has been turned on.
The +5V output may be trimmed ±6% via a single external trimpot or ﬁxed
resistor. The trimpot should be connected as shown in Figure 7 with its wiper
connected to pin 10 (Trim). A trimpot can also be used to determine the
value of a single ﬁxed resistor which should be connected as shown in Figure
8. Connect the resistor between pin 10 (Trim) and pin 9 (+5V Output) to trim
"down" the output voltage. Connect the resistor between pins 10 and 8 (Com-
mon) to trim "up" the output voltage. Fixed resistors should be metal-ﬁlm
types with absolute TCR’s less than 100ppm/°C to ensure stability.
Unlike most other DC/DC converters, TMP DC/DC's do not have their metal
case connected to one of their input pins. The "uncommitted" case is con-
nected to pin 4 which, depending on your system conﬁguration, should be
connected to either +Input (pin 3) or –Input (pin 2).
Threaded Inserts and Heatsink Installation
Figure 6. Driving the On/Off Control Pin
Figure 7. Trim Connections Using a Trimpot
CAUTION: Do not use the threaded inserts to bolt the converter down to a
PC board. That will place unnecessary force on the mounting pins. Instead,
the converter is held securely by only soldering the mounting pins.
Figure 8. Trim Connections Using Fixed Resistors
When attaching the heat sink from above the converter, use a maximum
torque of 2 inch-pounds (0.23 N-m) on the 4-40 bolts to avoid damaging the
threaded inserts. Use a tiny amount of fastener adhesive or 4-40 lockwash-
ers to secure the bolts.
Technical enquiries email: firstname.lastname@example.org, tel: +1 508 339 3000
MDC_TMP25-40W_B02 Page 6 of 6