LT3680
36V, 3.5A, 2.4MHz
Step-Down Switching Regulator
with 75µA Quiescent Current
FEATURES
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DESCRIPTION
The LT
®
3680 is an adjustable frequency (200kHz to
2.4MHz) monolithic buck switching regulator that accepts
input voltages up to 36V. A high efficiency 95m switch
is included on the die along with a boost Schottky diode
and the necessary oscillator, control, and logic circuitry.
Current mode topology is used for fast transient response
and good loop stability. Low ripple Burst Mode operation
maintains high efficiency at low output currents while
keeping output ripple below 15mV in a typical application.
In addition, the LT3680 can further enhance low output
current efficiency by drawing bias current from the output
when V
OUT
is above 3V. 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 flag signals when V
OUT
reaches
91% of the programmed output voltage. The LT3680 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.
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Wide Input Voltage Range: 3.6V to 36V
3.5A Maximum Output Current
Low Ripple (<15mV
P-P
) Burst Mode
®
Operation:
I
Q
= 75μA at 12V
IN
to 3.3V
OUT
Adjustable Switching Frequency: 200kHz to 2.4MHz
Low Shutdown Current: I
Q
< 1μA
Integrated Boost Diode
Synchronizable Between 250kHz to 2MHz
Power Good Flag
Saturating Switch Design: 95m On-Resistance
0.790V Feedback Reference Voltage
Output Voltage: 0.79V to 30V
Thermal Protection
Soft-Start Capability
Small 10-Pin Thermally Enhanced MSOP and
(3mm
×
3mm) DFN Packages
APPLICATIONS
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Automotive Battery Regulation
Power for Portable Products
Distributed Supply Regulation
Industrial Supplies
Wall Transformer Regulation
TYPICAL APPLICATION
5V Step-Down Converter
V
IN
6.3V TO 36V
V
IN
OFF ON
15k
10μF
680pF
63.4k
V
C
RT
PG
SYNC
536k
GND
FB
100k
47μF
50
0
0.5
2
1.5
1
2.5
OUTPUT CURRENT (A)
3
3.5
3680 G01
Efficiency
V
OUT
5V
3.5A
100
V
IN
= 12V
90
EFFICIENCY (%)
V
IN
= 34V
80
V
IN
= 24V
BD
BOOST
0.47μF 4.7μH
LT3680
SW
RUN/SS
70
60
V
OUT
= 5V
L = 4.7μH
f = 600kHz
3680 TA01a
3680fa
1
LINER [ LINEAR TECHNOLOGY ]
