HPH Series

www.murata-ps.com

MDC_HPH_A12 Page 8 of 12

Trim Equations

Where Vref = +1.225 Volts and Δ is the desired output voltage change. Note

that "Δ" is given as a small fraction, not a percentage.

A single resistor connected between Trim and +Sense will increase the output

voltage. A resistor connected between Trim and –Sense will decrease the output.

Remote On/Off Control

On the input side, a remote On/Off Control can be ordered with either polarity.

Positive: Standard models are enabled when the On/Off pin is left open or is

pulled high to +Vin with respect to –Vin. An internal bias current causes the

open pin to rise to +Vin. Some models will also turn on at lower intermediate

voltages (see Specifications). Positive-polarity devices are disable when the

On/Off is grounded or brought to within a low voltage (see Specifications) with

respect to –Vin.

Negative: Optional negative-polarity devices are on (enabled) when the On/Off

is grounded or brought to within a low voltage (see Specifications) with respect

to –Vin. The device is off (disabled) when the On/Off is left open or is pulled

high to +Vin with respect to –Vin.

Figure 7 – Trim adjustments to Decrease Output Voltage using a Fixed Resistor

Figure 8 – Driving the Positive Polarity On/Off Control Pin

Figure 9 – Driving the Negative Polarity On/Off Control Pin

Dynamic control of the On/Off function should be able to sink appropriate sig-

nal current when brought low and withstand appropriate voltage when brought

high. Be aware too that there is a finite time in milliseconds (see Specifications)

between the time of On/Off Control activation and stable, regulated output. This

time will vary slightly with output load type and current and input conditions.

There are three CAUTION’s for the On/Off Control:

CAUTION: To retain full output circuit isolation, control the On/Off from the input

side ONLY. If you must control it from circuits in the output, use some form of

optoisolation to the On/Off Control. This latter condition is unlikely because the

device controlling the On/Off would have to remain powered on and not be

powered from the converter..

CAUTION: While it is possible to control the On/Off with external logic if you

carefully observe the voltage levels, the preferred circuit is either an open

drain/open collector transistor or a relay (which can thereupon be controlled by

logic). The On/Off prefers to be set at +Vin (open pin) for the ON state, assum-

ing positive logic.

CAUTION: Do not apply voltages to the On/Off pin when there is no input power

voltage. Otherwise the converter may be permanently damaged.

1

3

4

5

8

7

6

9

+OUTPUT

+SENSE

TRIM

-SENSE

-OUTPUT

-INPUT

ON/OFF

CONTROL

+INPUT

LOAD

1

3

4

ON/OFF

CONTROL

-INPUT

+INPUT

+VCC

-

- 2

1

Δ

1.225 x Δ

where Δ =

- 2

1

Δ

where Δ =

ON/OFF CONTROL

CONTROL

+ Vcc

-INPUT