LT3686_15 Datasheet, PDF (1/28 Pages) Linear Technology – 37V/1.2A Step-Down Regulator in 3mm 3mm DFN

LT3686
37V/1.2A Step-Down
Regulator in 3mm × 3mm DFN
Features
n _{Wide Input Range:}
Operation from 3.6V to 37V
Overvoltage Lockout Protects Circuit Through
55V Transients
n _{Low Minimum On-Time:}
Converts 16V_IN to 3.3V_OUT at 2MHz
n _{1.2A Output Current}
n _{Adjustable Frequency: 300kHz to 2.5MHz}
n _{Constant Switching Frequency at Light Loads}
n _{Tracking and Soft-Start}
n _{Precision UVLO}
n _{Short-Circuit Robust}
n _{IQ in Shutdown <1µA}
n _{Internally Compensated}
n _{10-Lead 3mm × 3mm DFN Package}
Applications
n _{Automotive Systems}
n _{Battery-Powered Equipment}
n _{Wall Transformer Regulation}
n _{Distributed Supply Regulation}
Description
The LT^®3686 is a current mode PWM step-down DC/DC
converter with an internal 1.2A power switch, packaged in
10-lead 3mm × 3mm DFN. The wide input range of 3.6V to
37V makes the LT3686 suitable for regulating power from
a wide variety of sources, including 24V industrial supplies
and automotive batteries. Its high maximum frequency al-
lows the use of tiny inductors and capacitors, resulting in
a very small solution. Operating frequency above the AM
band avoids interfering with radio reception, making the
LT3686 particularly suitable for automotive applications.
Cycle-by-cycle current limit and DA current sense provide
protection against fault conditions. Soft-start and frequency
foldback eliminate input current surge during start-up. An
optional internal regulated active load at the output via
the BD pin keeps the LT3686 at full switching frequency
at light loads, resulting in low, predictable output ripple
above the audio and AM bands. Internal compensation and
an internal boost diode reduce external component count.
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.
Typical Application
3.3V Step-Down Converter
V_IN
6V TO 37V
2.2µF
V_IN
EN/UVLO
BD
BOOST
LT3686
MODE
SW
SS
DA
10nF
RT
GND
FB
15.4k
(V_IN 6V TO 16V AT 2.1MHz)
0.22µF
6.8µH
MBRM140
31.6k
V_OUT
3.3V
1.2A
10k
22µF
3686 TA01a
12V_IN Efficiency (2.1MHz)
90
80
3.3V_OUT
70
5V_OUT
60
50
40
30
20
10
0
0 200 400 600 800 1000 1200
LOAD CURRENT (mA)
3686 TA01b
3686fc
1