H48SC3R325PSFA Datasheet H48SC3R325PSFA | P7-P9

H48SC3R325_07122011

DESIGN CONSIDERATIONS

Input Source Impedance

The impedance of the input source connecting to the

DC/DC power modules will interact with the modules

and affect the stability. A low ac-impedance input source

is recommended. If the source inductance is more than

a few µH, we advise adding a 220 to 470 µF electrolytic

capacitor (ESR < 0.1 Ω at 100 kHz) mounted close to

the input of the module to improve the stability.

Layout and EMC Considerations

Delta’s DC/DC power modules are designed to operate

in a wide variety of systems and applications. For design

assistance with EMC compliance and related PWB

layout issues, please contact Delta’s technical support

team. An external input filter module is available for

easier EMC compliance design.

Safety Considerations

The power module must be installed in compliance with

the spacing and separation requirements of the

end-user’s safety agency standard, i.e., UL60950-1,

CSA C22.2 NO. 60950-1 2nd and IEC 60950-1 2nd :

2005 and EN 60950-1 2nd: 2006+A11+A1: 2010, if the

system in which the power module is to be used must

meet safety agency requirements.

Basic insulation based on 75 Vdc input is provided

between the input and output of the module for the

purpose of applying insulation requirements when the

input to this DC-to-DC converter is identified as TNV-2

or SELV. An additional evaluation is needed if the

source is other than TNV-2 or SELV.

When the input source is SELV, the power module meets

SELV (safety extra-low voltage) requirements. If the

input source is a hazardous voltage which is greater than

60 Vdc and less than or equal to 75 Vdc, for the module’s

output to meet SELV requirements, all of the following

must be met:

 The input source must be insulated from the ac

mains by reinforced or double insulation.

 The input terminals of the module are not operator

accessible.

 A SELV reliability test is conducted on the system

where the module is used, in combination with the

module, to ensure that under a single fault,

hazardous voltage does not appear at the module’s

output.

When installed into a Class II equipment (without

grounding), spacing consideration should be given to

the end-use installation, as the spacing between the

module and mounting surface have not been evaluated.

The power module has extra-low voltage (ELV) outputs

when all inputs are ELV.

This power module is not internally fused. To achieve

optimum safety and system protection, an input line fuse

is highly recommended. The safety agencies require a

normal-blow fuse with (TBD) A maximum rating to be

installed in the ungrounded lead. A lower rated fuse can

be used based on the maximum inrush transient energy

and maximum input current.

Soldering and Cleaning Considerations

Post solder cleaning is usually the final board assembly

process before the board or system undergoes electrical

testing. Inadequate cleaning and/or drying may lower the

reliability of a power module and severely affect the

finished circuit board assembly test. Adequate cleaning

and/or drying is especially important for un-encapsulated

and/or open frame type power modules. For assistance

on appropriate soldering and cleaning procedures,

please contact Delta’s technical support team.

H48SC3R325_07122011

FEATURES DESCRIPTIONS

Over-Current Protection

The module provides two over current protection levels.

When the output current exceeds the low current limit

level, the module will endure current limiting till the

output voltage is lower than 0.2V. If the output current

exceeds the high current limit level, the module will shut

down immediately.

The modules will try to restart after shutdown (hiccup

mode). If the overload condition still exists, the module

will shut down again. This restart trial will continue until

the load condition is corrected.

Over-Voltage Protection

The modules include an internal output over-voltage

protection circuit, which monitors the voltage on the

output terminals. If this voltage exceeds the over-voltage

set point, the module will shut down.

The modules will try to restart after shutdown (hiccup

mode). If the over voltage still exists, the module will

shut down again. This restart trial will continue until the

voltage condition is corrected

Over-Temperature Protection

The over-temperature protection consists of circuitry

that provides protection from thermal damage. If the

temperature exceeds the over-temperature threshold

the module will shut down.

The module will try to restart after shutdown. If the

over-temperature condition still exists during restart, the

module will not start up. This restart trial will continue

until the temperature is within specification.

Remote On/Off

The remote on/off feature on the module can be either

negative or positive logic. Negative logic turns the

module on during logic low and off during logic high.

Positive logic turns the modules on during logic high and

off during logic low.

Remote on/off can be controlled by an external switch

between the on/off terminal and the Vi(-) terminal. The

switch can be an open collector or open drain.

For negative logic if the remote on/off feature is not

used, please short the on/off pin to Vi(-). For positive

logic if the remote on/off feature is not used, please

leave the on/off pin to floating.

Vo(+)Vi(+)

Vo(-)

Sense(-)

Sense(+)

Vi(-)

ON/OFF

Figure 16: Remote on/off implementation

Remote Sense

Remote sense compensates for voltage drops on the

output by sensing the actual output voltage at the point

of load. The voltage between the remote sense pins

and the output terminals must not exceed the output

voltage sense range given here:

[Vo(+) – Vo(–)] – [SENSE(+) – SENSE(–)] ≤ 10% × Vout

This limit includes any increase in voltage due to

remote sense compensation and output voltage set

point adjustment (trim).

Vi(-)

Vi(+)

Vo(-)

Vo(+)

Sense(+)

Sense(-)

Resistance

Contact

Contact and Distribution

Losses

Figure 17: Effective circuit configuration for remote sense

operation

If the remote sense feature is not used to regulate the

output at the point of load, please connect SENSE(+) to

Vo(+) and SENSE(–) to Vo(–) at the module.

The output voltage can be increased by both the

remote sense and the trim; however, the maximum

increase is the larger of either the remote sense or the

trim, not the sum of both.

When using remote sense and trim, the output voltage

of the module is usually increased, which increases the

power output of the module with the same output

current.

Care should be taken to ensure that the maximum

output power does not exceed the maximum rated

power.

H48SC3R325_07122011

FEATURES DESCRIPTIONS (CON.)

Output Voltage Adjustment (TRIM)

To increase or decrease the output voltage set point,

the modules may be connected with an external

resistor between the TRIM pin and either the

SENSE(+) or SENSE(-). The TRIM pin should be left

open if this feature is not used.

Figure 18: Circuit configuration for trim-down (decrease

output voltage)

If the external resistor is connected between the TRIM

and SENSE (-) pins, the output voltage set point

decreases (Fig. 18). The external resistor value

required to obtain a percentage of output voltage

change △% is defined as:

Rtrim down=

100

∆

2−











ΚΩ

Ex. When Trim-down 10% (3.3V×0.9=2.97V)

Vo 3.3:= V ∆ 10:=

100

∆

2− 8= KΩ

Figure 19: Circuit configuration for trim-up (increase output

voltage)

If the external resistor is connected between the TRIM

and SENSE (+) the output voltage set point increases

(Fig. 19). The external resistor value required to obtain

a percentage output voltage change △% is defined

as:

Rtrim up=

Vo 100 ∆+

(

)

⋅

1.225∆⋅

100 2∆+

∆

−













Ω

Ex. When Trim-up +10%(3.3V×1.1=3.63V)

Vo 3.3:= V

∆

10:=

Vo 100 ∆+

()

⋅

1.225 ∆⋅

100 2 ∆⋅+

∆

− 17.633= KΩ

The output voltage can be increased by both the remote

sense and the trim, however the maximum increase is

the larger of either the remote sense or the trim, not the

sum of both.

When using remote sense and trim, the output voltage

of the module is usually increased, which increases the

power output of the module with the same output

current?

Care should be taken to ensure that the maximum

output power of the module remains at or below the

maximum rated power.

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H48SC3R325PSFA

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