1
DEMO MANUAL DC236
DESIGN-READY SWITCHERS
LTC1628
2-Phase Constant-Frequency
Synchronous, Dual-Output
DC/DC Converter
This demonstration board provides 3.3V/4A and 5V/4A
outputs using a low EMI, 2-phase, adjustable, dual switch-
ing regulator controller. This design is ideally suited for
notebook computer system power supply applications.
Operating the two high side MOSFETs 180
°
out of phase
significantly reduces peak input ripple current, thereby
reducing radiated and conducted EMI. External parts
count, cost and size are minimized in this design. Output
voltages can be externally set to as low as 0.8V. The
controllers have overcurrent latch-off, which can be exter-
nally defeated, as well as internal current foldback for
overload situations. The overcurrent latch-off on one
controller can be configured to shut off the other output.
A soft latch for overvoltage conditions is also provided. In
addition to the two high current outputs, on-chip 5V/50mA
and 3.3V/25mA linear regulators are also included. In the
optional standby mode, these internal regulators are ca-
pable of powering external system wake-up circuitry when
both high current controllers are shut down. Two low
current modes of operation are available: Burst Mode
TM
operation offers highest efficiency while Burst Disable
mode provides constant-frequency operation down to 1%
of maximum designed load. The frequency is externally
DC-controlled over a 130kHz to 300kHz range. The con-
troller can operate at up to 99% duty cycle for very low
dropout conditions. The demonstration board operates on
an input supply of from 5.2V to 30V. Refer to the LTC
®
1628
data sheet for other possible configurations. Gerber files
for this circuit board are available. Call the LTC factory.
DC236 BP
Efficiency vs Load
Demo Circuit 236A
OUTPUT CURRENT (A)
0.001
EFFICIENCY (%)
10
DC236TP01
0.01
0.1
1
100
90
80
70
60
50
5V OUTPUT
3.3V OUTPUT
V
IN
= 15V
Input Voltage Range
Input Voltage Limited by External MOSFET Drive and Breakdown Requirements
5.2V to 30V
Outputs
Output Voltage: Controller 1; Externally Adjustable; 0 to 3A, 4A Pk
5V
±
0.10V
Output Voltage: Controller 2; Externally Adjustable; 0 to 3A, 4A Pk
3.33V
±
0.067V
5V Linear Regulator
5V
±
4%
3.3V Linear Regulator
3.3V
±
4%
Typical Output Ripple at 10MHz BW; 300kHz; I
O
= 1A; 3.3V and 5V Outputs; V
IN
= 15V
20mV
P-P
Operating Temperature Range: 0
°
C to 50
°
C (continued on Page 2)
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
DESCRIPTIO
U
PERFOR A CE SU ARY
U
W
WW
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO
U
U
W
