LT3684
36V, 2A, 2.8MHz Step-Down
Switching Regulator
FEATURES
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DESCRIPTION
The LT
®
3684 is an adjustable frequency (300kHz to 2.8MHz)
monolithic buck switching regulator that accepts input
voltages up to 34V (36V maximum). A high efficiency
0.18Ω 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. The LT3684’s
high operating frequency allows the use of small, low cost
inductors and ceramic capacitors resulting in low output
ripple while keeping total solution size to a minimum.
The low current shutdown mode 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
90% of the programmed output voltage. The LT3684 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.
All other trademarks are the property of their respective owners.
Wide Input Range: 3.6V to 34V Operating,
36V Maximum
2A Maximum Output Current
Adjustable Switching Frequency: 300kHz to 2.8MHz
Low Shutdown Current: I
Q
< 1µA
Integrated Boost Diode
Power Good Flag
Saturating Switch Design: 0.18Ω On-Resistance
1.265V Feedback Reference Voltage
Output Voltage: 1.265V to 20V
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
3.3V Step-Down Converter
V
IN
4.5V TO
34V
V
IN
OFF ON
16.2k
4.7µF
330pF
V
C
LT3684
RT
PG
60.4k
GND
BIAS
324k
FB
200k
22µF
40
30
0
0.5
1
1.5
LOAD CURRENT (A)
2
3684 TA01b
Efficiency
V
OUT
3.3V
2A
0.47µF
90
80
70
60
50
V
IN
= 12V
V
OUT
= 3.3V
L = 4.7µH
f = 800kHz
BD
BOOST
SW
4.7µH
RUN/SS
3684 TA01
EFFICIENCY (%)
3684f
1
LINER [ LINEAR TECHNOLOGY ]
