LT3695 Datasheet, PDF (1/28 Pages) Linear Technology – 1A Fault Tolerant Micropower Step-Down Regulator

LT3695
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 _{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 is an adjustable frequency (250kHz to 2.2MHz)
monolithic buck switching regulator that accepts input volt-
ages up to 36V and can safely sustain transient voltages
up to 60V. The device includes 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 tolerates 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 against short-circuit condi-
tions. Frequency foldback and thermal shutdown provide
additional protection.
The LT3695 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 100k
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
3695f
1