LT3695 Series
1A Fault Tolerant Micropower
Step-Down Regulator
FEATURES
DESCRIPTION
The LT®3695 series are adjustable frequency (250kHz to
2.2MHz)monolithicbuckswitchingregulatorsthataccept
input voltages up to 36V and can safely sustain transient
voltages up to 60V. The devices include a high efficiency
switch, aboostdiode, andthenecessaryoscillator, control
and logic circuitry. Current mode topology is used for fast
transient response and good loop stability. A SYNC pin
allowstheusertosynchronizetheparttoanexternalclock,
and to choose between low ripple Burst Mode operation
and standard PWM operation.
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Wide Input Range:
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuits Through
60V Transients
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FMEA Fault Tolerant:
Output Stays at or Below Regulation Voltage
During Adjacent Pin Short or When a Pin Is Left
Floating
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1A Output Current
Low Ripple (< 15mV ) Burst Mode® Operation
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P-P
IN
I = 75μA for 12V to 3.3V with No Load
Q
OUT
The LT3695 regulators tolerate adjacent pin shorts or
an open pin without raising the output voltage above its
programmed value.
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Adjustable Switching Frequency: 250kHz to 2.2MHz
Short-Circuit Protected
Synchronizable Between 300kHz and 2.2MHz
Output Voltage: 0.8V to 20V
Low ripple Burst Mode operation maintains high effi-
ciency at low output currents while keeping output ripple
below 15mV in a typical application. 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). Protection circuitry senses the
current in the power switch and external Schottky catch
diodetoprotecttheLT3695regulatorsagainstshort-circuit
conditions. Frequency foldback and thermal shutdown
provide additional protection.
Power Good Flag
Fixed Output Voltage Versions for 3.3V and 5V Available
Small, Thermally Enhanced 16-Pin MSOP Package
APPLICATIONS
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Automotive Battery Regulation
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Automotive Entertainment Systems
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Distributed Supply Regulation
Industrial Supplies
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L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
The LT3695 series is available in a thermally enhanced
16-pin MSOP package.
TYPICAL APPLICATION
Efficiency
100
5V Step-Down Converter
V
V
IN
V
= 5V
OUT
5V
OUT
6.9V TO 36V
90
80
TRANSIENT TO 60V
0.9A, V > 6.9V
1A, V > 12V
IN
IN
V
BD
BOOST
IN
RUN/SS
V
OUT
= 3.3V
2.2μF
ON OFF
40.2k
0.22μF
10μH
V
C
SW
LT3695
RT
70
PG
DA
FB
536k
16.2k
470pF
SYNC
GND PGND
60
50
V
= 12V
IN
102k
10μF
L = 10μH
f = 800kHz
3695 TA01a
f = 800kHz
0
0.2
0.4
0.6
0.8
1
LOAD CURRENT (A)
3695 TA01b
3695fa
1