LT3695_15 Datasheet, PDF (1/30 Pages) Linear Technology – 1A Fault Tolerant Micropower Step-Down Regulator

LT3695 Series
1A Fault Tolerant Micropower
Step-Down Regulator
FEATURES
n _{Wide Input Range:}
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuits Through
60V Transients
n _{FMEA Fault Tolerant:}
Output Stays at or Below Regulation Voltage
During Adjacent Pin Short or When a Pin Is Left
Floating
n _{1A Output Current}
n _{Low Ripple (< 15mVP-P) Burst Mode}^® _Operation
I_Q = 75μA for 12V_IN to 3.3V_OUT with No Load
n _{Adjustable Switching Frequency: 250kHz to 2.2MHz}
n _{Short-Circuit Protected}
n _{Synchronizable Between 300kHz and 2.2MHz}
n _{Output Voltage: 0.8V to 20V}
n _{Power Good Flag}
n _{Fixed Output Voltage Versions for 3.3V and 5V Available}
n _{Small, Thermally Enhanced 16-Pin MSOP Package}
APPLICATIONS
n _{Automotive Battery Regulation}
n _{Automotive Entertainment Systems}
n _{Distributed Supply Regulation}
n _{Industrial Supplies}
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.
DESCRIPTION
The LT^®3695 series are adjustable frequency (250kHz to
2.2MHz) monolithic buck switching regulators that accept
input voltages up to 36V and can safely sustain transient
voltages up to 60V. The devices include a high efficiency
switch, 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 LT3695 regulators tolerate adjacent pin shorts or
an open pin without raising the output voltage above its
programmed value.
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
diode to protect the LT3695 regulators against short-circuit
conditions. Frequency foldback and thermal shutdown
provide additional protection.
The LT3695 series is available in a thermally enhanced
16-pin MSOP package.
TYPICAL APPLICATION
V_IN
6.9V TO 36V
TRANSIENT TO 60V
5V Step-Down Converter
2.2μF ON OFF
16.2k 40.2k
470pF
V_IN
RUN/SS
BD
BOOST
V_C
SW
RT ^LT3695
PG
DA
SYNC
FB
GND PGND
0.22μF 10μH
536k
102k
V_OUT
5V
0.9A, V_IN > 6.9V
1A, V_IN > 12V
10μF
f = 800kHz
3695 TA01a
Efficiency
100
V_OUT = 5V
90
V_OUT = 3.3V
80
70
60 _{VIN = 12V}
L = 10μH
f = 800kHz
50
0
0.2 0.4 0.6
LOAD CURRENT (A)
0.8
1
3695 TA01b
3695fa
1