LT3695 Series
1
3695fa
TYPICAL APPLICATION
DESCRIPTION
1A Fault Tolerant Micropower
Step-Down Regulator
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 effi ciency
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.
5V Step-Down Converter
FEATURES
APPLICATIONS
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 (< 15mV
P-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
n
Automotive Battery Regulation
n
Automotive Entertainment Systems
n
Distributed Supply Regulation
n
Industrial Supplies
Effi ciency
V
IN
BD
LT3695
RUN/SS
V
C
0.22μF
V
OUT
5V
0.9A, V
IN
> 6.9V
1A, V
IN
> 12V
102k
f = 800kHz
536k
10μH
10μF
3695 TA01a
470pF
2.2μF
V
IN
6.9V TO 36V
TRANSIENT TO 60V
RT
PG
40.2k
16.2k
SYNC
BOOST
ON OFF
SW
DA
FB
GND
PGND
LOAD CURRENT (A)
0
50
EFFICIENCY (%)
60
70
80
90
100
0.2
0.4
0.6
0.8
1
V
OUT
= 5V
V
OUT
= 3.3V
V
IN
= 12V
L = 10μH
f = 800kHz
3695 TA01b
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.
