LT3682 Datasheet, PDF (1/24 Pages) Linear Technology – 1A Micropower Step-Down

LT3682
1A Micropower Step-Down
Switching Regulator
FEATURES
n _{Wide Input Range:}
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuits through
60V Transients
n _{1A Output Current}
n _{Low Ripple Burst Mode}^® _Operation
I_Q = 75μA at 12V_IN to 3.3V_OUT
Output Ripple < 15mV_P-P
n _{Adjustable Switching Frequency: 250kHz to 2.2MHz}
n _{Short-Circuit Protected}
n _{Synchronizable Between 300kHz and 2.2MHz}
n _{0.8V Feedback Reference Voltage}
n _{Output Voltage 0.8V to 20V}
n _{Soft-Start Capability}
n _{Power Good Flag}
n _{Small 12-Pin Thermally Enhanced 3mm × 3mm}
DFN Package
APPLICATIONS
n _{Automotive Battery Regulation}
n _{Automotive Entertainment Systems}
n _{Industrial Supplies}
n _{Power for Portable Products}
n _{Distributed Supply Regulation}
DESCRIPTION
The LT^®3682 is an adjustable frequency (250kHz to
2.2MHz) monolithic buck switching regulator that accepts
input voltages up to 36V. A high efficiency 0.5Ω switch is
included on the device along with a boost diode and the
necessary oscillator, control, and logic circuitry. Current
mode topology is used for fast transient response and good
loop stability. A SYNC pin allows the user to synchronize the
part to an external clock, and to choose between Low Ripple
Burst Mode operation and standard PWM operation.
The Low Ripple Burst Mode maintains high efficiency at
low output currents while keeping output ripple below
15mV in typical applications. 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 90% of the programmed output voltage.
Protection circuitry senses the current in the power switch
and external Schottky catch diode to protect the LT3682
against short-circuit conditions. Frequency foldback and
thermal shutdown provide additional protection.
The LT3682 is available in a 12-Pin 3mm × 3mm DFN with
exposed pad for low thermal resistance.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
TYPICAL APPLICATION
5V Step-Down Converter
V_IN
6.9V TO 36V
TRANSIENT TO 60V
2.2μF
ON OFF
16.2k
470pF
40.2k
V_IN
RUN/SS
BD
BOOST
V_C
R_T
LT3682
SW
PG
DA
SYNC _{GND PGND} FB
f = 800kHz
0.22μF
10μH
V_OUT
5V
0.9A, V_IN r 6.9V
1A, V_IN r 12V
536k
102k
10μF
3682 TA01
Efficiency
100
V_OUT = 5V
90
V_OUT = 3.3V
80
70
60
50
0
V_IN = 12V
L = 10µH
f = 800 kHz
0.2 0.4 0.6 0.8
1
LOAD CURRENT (A)
3682 TA01b
3682f
1