HBC48T25120 Datasheet, PDF (4/16 Pages) Power-One – HBC48T25120 DC-DC Converter Data Sheet

HBC48T25120 DC-DC Converter Data Sheet
36-75 VDC Input; 12 VDC @ 25 A Output
Operations
Input and Output Impedance
These power converters have been designed to be
stable with no external capacitors when used in low
inductance input and output circuits.
In many applications, the inductance associated with
the distribution from the power source to the input of
the converter can affect the stability of the converter.
The addition of a 100 µF electrolytic capacitor with
an ESR < 1 Ω across the input helps to ensure
stability of the converter. In many applications, the
user has to use decoupling capacitance at the load.
The power converter will exhibit stable operation with
external load capacitance up to 15,000 µF on the
output.
Additionally, see the EMC section of this data sheet
for discussion of other external components which
may be required for control of conducted emissions.
ON/OFF (Pin 2)
The ON/OFF pin is used to turn the power converter
on or off remotely via a system signal. There are two
remote control options available, positive and
negative logic, with both referenced to Vin(-). A
typical connection is shown in Fig. A.
VIN (+)
VOUT (+)
ON/OFF
SENSE (+)
VIN
(Top View)
TRIM
Rload
CASE
SENSE (-)
CONTROL
INPUT
VIN (-)
VOUT (-)
Fig. A: Circuit configuration for ON/OFF function.
The positive logic version turns on when the ON/OFF
pin is at a logic high and turns off when at a logic
low. The converter is on when the ON/OFF pin is left
open. See the Electrical Specifications for logic
high/low definitions.
The negative logic version turns on when the pin is
at a logic low and turns off when the pin is at a logic
high. The ON/OFF pin can be hardwired directly to
Vin(-) to enable automatic power up of the converter
without the need of an external control signal.
The ON/OFF pin is internally pulled up to 5 VDC
through a resistor. A properly de-bounced
mechanical switch, open-collector transistor, or FET
can be used to drive the input of the ON/OFF pin.
The device must be capable of sinking up to 0.2 mA
at a low level voltage of  0.8 V. An external voltage
source (±20 V maximum) may be connected directly
to the ON/OFF input, in which case it must be
capable of sourcing or sinking up to 1 mA depending
on the signal polarity. See the Startup Information
section for system timing waveforms associated with
use of the ON/OFF pin.
Remote Sense (Pins 6 and 8)
The remote sense feature of the converter
compensates for voltage drops occurring between
the output pins of the converter and the load. The
SENSE(-) (Pin 6) and SENSE(+) (Pin 8) pins should
be connected at the load or at the point where
regulation is required (see Fig. B).
VIN (+)
VOUT (+)
Rw
ON/OFF
SENSE (+)
VIN
(Top View)
TRIM
Rload
CASE
SENSE (-)
VIN (-)
Rw
VOUT (-)
Fig. B: Remote sense circuit configuration.
CAUTION
If remote sensing is not utilized, the SENSE(-) pin must be
connected to the Vout(-) pin (Pin 5), and the SENSE(+) pin must
be connected to the Vout(+) pin (Pin 9) to ensure the converter
will regulate at the specified output voltage. If these connections
are not made, the converter will deliver an output voltage that is
slightly higher than the specified data sheet value.
Because the sense leads carry minimal current,
large traces on the end-user board are not required.
However, sense traces should be run side by side
and located close to a ground plane to minimize
system noise and ensure optimum performance.
The converter’s output overvoltage protection (OVP)
circuitry senses the voltage across Vout(+) and
Vout(-), and not across the +/- sense lines, so the
resistance (and resulting voltage drop) between the
output pins of the converter and the load should be
minimized to prevent unwanted triggering of the
OVP.
When utilizing the remote sense feature, care must
be taken not to exceed the maximum allowable
output power capability of the converter, which is
equal to the product of the nominal output voltage
and the allowable output current for the given
conditions.
MCD10127 Rev. 1.1, 09-Jun-10
Page 4 of 16
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