Linear Technology LT3480 Manual

FEATURES
n
Wide Input Range:
Operation from 3.6V to 36V
Over-Voltage Lockout Protects Circuits
through 60V Transients
n
2A Maximum Output Current
n
Low Ripple Burst Mode
70μA IQ at 12VIN to 3.3VOUT
Output Ripple < 15mV
n
Adjustable Switching Frequency: 200kHz to 2.4MHz
n
Low Shutdown Current: IQ < 1μA
n Integrated Boost Diode
n
Synchronizable Between 250kHz to 2MHz
n
Power Good Flag
n
Saturating Switch Design: 0.25 On-Resistance
n
0.790V Feedback Reference Voltage
n
Output Voltage: 0.79V to 20V
n
Soft-Start Capability
n
Small 10-Pin Thermally Enhanced MSOP and
(3mm × 3mm) DFN Packages
APPLICATIONS
n
Automotive Battery Regulation
n Power for Portable Products
n
Distributed Supply Regulation
n
Industrial Supplies
TYPICAL APPLICATION
3.3V Step-Down Converter
V
IN
4.5V TO 36V
TRANSIENT
TO 60V
OFF ON
14k
4.7μF
470pF
40.2k
® Operation
V BD
IN
RUN/SS BOOST
0.47μF
4.7μH
V SW
LT3480
C
RT
PG
316k
SYNC
FB
GND
100k
3480 TA01
36V, 2A, 2.4MHz Step-Down
Switching Regulator with
70µA Quiescent Current
DESCRIPTION
®
The LT 3480 is an adjustable frequency (200kHz to
2.4MHz) monolithic buck switching regulator that ac-
cepts input voltages up to 36V (60V maximum). A high
effi ciency 0.25 switch is included on the die along with
a boost Schottky diode and the necessary oscillator, con-
trol, and logic circuitry. Current mode topology is used
for fast transient response and good loop stability. Low
ripple Burst Mode operation maintains high effi ciency at
low output currents while keeping output ripple below
15mV in a typical application. In addition, the LT3480 can
further enhance low output current effi ciency by draw-
ing bias current from the output when V
Shutdown reduces input supply current to less than 1μA
while a resistor and capacitor on the RUN/SS pin provide a
controlled output voltage ramp (soft-start). A power good
fl ag signals when V
OUT
output voltage. The LT3480 is available in 10-Pin MSOP
and 3mm × 3mm DFN packages with exposed pads for
low thermal resistance.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
V
100
OUT
3.3V
2A
90
80
70
60
22μF
50
0
LT3480
is above 3V.
OUT
reaches 86% of the programmed
Effi ciency
V = 5V
OUT
V = 3.3V
OUT
V = 12V
IN
L = 5.6μH
F = 800 kHz
0.5 1.0 1.5 2
LOAD CURRENT (A)
3480 TA01b
3480fb
1