1
DEMO MANUAL DC252
DESIGN-READY SWITCHER
LTC1736 5-Bit VID Constant
Frequency Synchronous DC/DC Converter
, LTC and LT are registered trademarks of Linear Technology Corporation.
DESCRIPTIO
U
PERFOR A CE SU
ARY
U
W
W
W
Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation.
Demonstration Circuit DC252 is designed for mobile 5-bit
VID-programmed notebook CPU applications using the
LTC
®
1736 switching regulator controller. A high perfor-
mance, constant frequency current mode architecture
generates a precise low voltage CPU core supply. Protec-
tion features include an externally defeatable overcurrent
latchoff and internal current foldback for overload condi-
tions. A soft-latched crowbar monitors the output voltage
for overvoltage protection. OPTI-LOOP
TM
compensation
allows the transient response to be optimized over a wide
range of output capacitance and ESR values. The circuit
was designed for a 5V to 24V input range but allows a 4.5V
to 28V range (limited by the external MOSFETs). Strong
output drivers easily handle large power MOSFETs effi-
ciently. Output voltages can be configured according to
Intel mobile VID standards of 0.9V to 2.0V. An internal
power-good circuit monitors the output voltage for out-of-
regulation conditions. External frequency synchronization
is provided, as are three modes of operation: Burst Mode
TM
operation to reduce switching losses and maintain high
operating efficiencies, burst inhibit/forced continuous
mode and a low noise pulse-skipping mode that provides
constant frequency operation down to 1% maximum load
currents with low quiescent current. This results in a
power supply that has very high efficiency, low ripple and
fast transient response.
Gerber files for this circuit board
are available. Call the LTC factory.
PARAMETER
CONDITIONS
VALUE
Input Voltage Range
(Maximum Input Voltage Limited By External MOSFET and Input Capacitor)
5V to 24V
Output
Output Voltage (Programmed with a 5-Bit Mobile VID Code)
0.9V to 2.0V
Max Output Current (Continuous)
11.0A
Max Output Current (Peak)
12A
Typical Output Ripple Measured with 10MHz Bandwidth (Burst Mode Operation) I
O
= 100mA
45mV
P-P
Typical Output Ripple Measured with 10MHz Bandwidth (Continuous) I
O
= 5A
20mV
P-P
V
IN
Line Regulation 5V to 24V
0.002%/V
LOAD CURRENT (A)
10mA
100mA
1A
10A
EFFICIENCY (%)
252 TA01
100
90
80
70
60
50
40
V
IN
= 5V
EXTV
CC
= 5V
V
IN
= 24V
V
IN
= 15V
Efficiency
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTOS
U
U
W
Solder Side
Component Side
