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FUNCTIONAL DESCRIPTION
OVERVIEW
The DCP02 offers up to 2W of unregulated output
power from a 5V, 12V, 15V, or 24V input source with
a typical efficiency of up to 89%. This efficiency is
achieved
through
highly
technology and the implementation of a custom
power stage and control IC. The circuit design uses
an advanced BiCMOS/DMOS process.
POWER STAGE
The DCP02 uses a push-pull, center-tapped topology
switching at 400kHz (divide-by-2 from an 800kHz
oscillator).
OSCILLATOR AND WATCHDOG
The
onboard
800kHz
switching frequency via a divide-by-2 circuit. The
oscillator can be synchronized to other DCP02
circuits or an external source, and is used to
minimize system noise.
CONSTRUCTION
The basic construction of the DCP02 is the same as
standard ICs; there is no substrate within the molded
package. The DCP02 is constructed using an IC,
rectifier diodes, and a wound magnetic toroid on a
leadframe. Since there is no solder within the
package, the DCP02 does not require any special
printed circuit board (PCB) assembly processing.
This architecture results in an isolated DC/DC
converter with inherently high reliability.
THERMAL SHUTDOWN
The DCP02 is protected by a thermal-shutdown
circuit. If the on-chip temperature exceeds +150
°
C,
the device will shut down. Once the temperature falls
below +150
°
C, normal operation resumes.
SYNCHRONIZATION
In the event that more than one DC/DC converter is
needed
onboard,
beat
electrical interference can be generated.
DCP
02
V
OUT 1
V
SUPPLY
V
S
0V
V
+ V
OUT 1
OUT 2
SYNC
0V
COM
DCP
02
V
OUT 2
V
S
0V
SYNC
0V
C
requires a low-ESR ceramic capacitor: 5V to 15V version is 2.2 F;
24V version is minimum 0.47 F. C
= 1.0 F.
IN
OUT
m
NOTE: (1)
SBVS011E–MARCH 2000–REVISED AUGUST 2006This interference occurs because of the small
variations in switching frequencies between the
DC/DC converters.
The DCP02 overcomes this interference by allowing
devices to be synchronized to one another. Up to
eight devices can be synchronized by connecting the
SYNC pins together, taking care to minimize the
capacitance of tracking. Stray capacitance (> 10pF)
has the effect of reducing the switching frequency, or
even
stopping
the
oscillator
recommended that power and ground lines be
star-connected.
integrated
packaging
circuit.
It
is
also
It should be noted that if synchronized devices are
used at start up, all devices will draw maximum
current simultaneously. This configuration can cause
the input voltage to dip; if it dips below the minimum
input voltage (4.5V), the devices may not start up. A
2.2
μ
F capacitor should be connected close to the
input pins.
oscillator
generates
the
If more than eight devices are to be synchronized, it
is recommended that the SYNC pins be driven by an
external device. Details are contained in Application
Report
SBAA035, External Synchronization of the
DCP01/02 Series of DC/DC Converters
, available for
download from
www.ti.com
.
A watchdog circuit checks the operation of the
oscillator circuit. The oscillator can be stopped by
pulling the SYNC pin low. The output pins will be
tri-stated, which occurs in 2
μ
s.
frequencies
and
other
Figure 7. Connecting the DCP02 in Series
6
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