TYPICAL PERFORMANCE CURVES
At T
A
= +25°C, V
S
= 5V, I
O
= 10mA, C
O
= 0.1µF, unless otherwise specified.
(Cont.)
DCR010505P OUTPUT VOLTAGE NOISE
AT 100% LOAD (100MHz Bandwidth)
DCR010505P OUTPUT VOLTAGE RIPPLE
AT 100% LOAD (20MHz Bandwidth)
20mV/div
200ns/div
5mV/div
200ns/div
FUNCTIONAL DESCRIPTION
OVERVIEW
The DCR01 series offers isolation from an unregulated
power supply operating from a choice of input voltages. The
DCR01’s provide a variety of regulated output voltages at a
nominal output power of 1W or above.
POWER STAGE
The input supply is chopped at a frequency of 400kHz
(internal oscillator divided by 2), which is used to drive the
center-tapped toroidal transformer.
RECTIFICATION
The transformer’s output is full wave rectified and smoothed
by the external capacitor connected to V
REC
.
REGULATOR
The internal low drop-out regulator provides a well-regu-
lated output voltage, throughout the operating range of the
device.
OSCILLATOR AND WATCHDOG
The DCR01 uses an internal saw-tooth generator to provide
the 800kHz on-board oscillator that is used to drive the
power switching circuit. The operation of the oscillator is
monitored by the watchdog, which will tri-state the output
driver circuit if the oscillator fails, or if the SYNC pin is
taken low, (shutdown mode). When the SYNC pin is re-
turned high, normal operation resumes.
SYNCHRONIZATION
If more than one DCR01 is being used, beat frequencies and
other electrical interference can be generated. This is due to
the small variations in switching frequencies between the
converters.
7
The DCR01 overcomes this by allowing devices to be
synchronized to one another. Up to eight devices can be
synchronized by connecting the SYNC pins together, with
care being taken to minimize the capacitance of tracking.
Significant stray capacitance on the SYNC pin will have the
effect of reducing the frequency of the internal oscillator. If
this is large, the DCR01 may be taken out with its optimized
operating parameters and saturation of the magnetics may
result, damaging the device.
If devices are synchronized, it should be noted that all
devices will draw maximum current simultaneously at start
up. This can cause the input voltage to dip. Should it fall
below the minimum input voltage, the devices may not start
up. A 2.2µF capacitor (low ESR) should be connected as
close to the device input pins as possible for the 5V input
devices and a 0.47µF capacitor for the 12V and 24V devices.
If more than eight devices are required to be synchronized,
it is recommended that external synchronization be used.
Details are contained in Burr-Brown’s Application Bulletin
AB-153.
CONSTRUCTION
The DCR01 is manufactured using the same technology as
standard IC packages. There is no substrate within the
package. The DCR01 is constructed using a driver IC, Low
Dropout Voltage Regulator, rectifier diodes and a wound
magnetic toroid, all mounted on a leadframe. The DCR01
requires no special PCB assembly processing, as there is no
solder within the package. The result is an isolated DC/DC
converter with inherently high reliability.
ADDITIONAL FUNCTIONS
DISABLE/ENABLE
The DCR01 can be disabled or enabled by driving the SYNC
pin using an open drain CMOS gate. If the SYNC pin is
®
DCR01
BURR-BROWN [ BURR-BROWN CORPORATION ]
