1
DEMO MANUAL DC094
DESIGN READY SWITCHER
LTC1435 Constant Frequency
Synchronous DC/DC Converter
DESCRIPTIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
This results in a power supply that has very high
efficiency, low ripple and fast transient response. At
low output currents the LTC1435 automatically switches
to Burst Mode
TM
operation to reduce switching losses
and maintain high operating efficiencies. Additionally,
the supply current can be shut down to less than
20µA with an input voltage of 10V. This feature is an
absolute necessity to maximize battery life in portable
applications. Gerber files for this circuit board are avail-
able. Call the LTC factory.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO
U
U
W
Efficiency
LOAD CURRENT (mA)
1
EFFICIENCY (%)
100
90
80
70
60
50
10 100
DM094 TPC01
1000 4000
V
IN
= 10V
SFB = INT V
CC
V
OUT
= 5V
V
OUT
= 2.5V
V
OUT
= 3.3V
PERFOR A CE SU ARY
UWWW
Operating Temperature Range 0
°
C to 50
°
C
Input Voltage Range
Maximum Input Voltage (Limited by External MOSFET and Input Capacitor) 4.5V to 28V
Output Output Voltage (Jumper Selectable) 1.8V, 2.5V, 2.9V, 3.3V, 5V
Maximum Output Current (Continuous) 3A
Maximum Output Current (Peak) 3.5A
Typical Output Ripple at 10MHz Bandwidth (Burst Mode
Operation) I
O
= 100mA 50mV
P-P
Typical Output Ripple at 10MHz Bandwidth (Continuous) I
O
= 1A 35mV
P-P
V
IN
Line Regulation, 6V to 20V 0.002%/V
I
OUT
Load Regulation, No Load to Full Rated Output –1%
I
Q
Supply Current with No Load at 10V Input (Typical), SFB = INT V
CC
, EXT V
CC
= 5V 50µA
Supply Current in Shutdown (Typical), V
IN
= 10V 15µA
I
EXTVCC
EXT V
CC
Pin Current, V
EXTVCC
= 5V, V
IN
= 10V, No Load 650µA
V
RUN
Run Pin Threshold (Typical) 1.3V
Frequency Operating Frequency (Typical), C
OSC
= 68pF
170kHz
DM094 BP
Demonstration Circuit 094 is a constant frequency step-
down (buck) regulator implemented entirely in surface
mount using the LTC
®
1435 switching regulator controller.
The output voltage is programmable from 1.8V to 5V via
a jumper. The input voltage can range from 4.5V to 28V
(limited by the external MOSFETs). The circuit highlights
the capabilities of the LTC1435 which uses a current
mode, constant frequency architecture to switch a pair of
N-channel power MOSFETs while providing 99% maxi-
mum duty cycle. Operating efficiencies exceeding 90%
are obtained.
