LT3686
37V/1.2A Step-Down
Regulator in 3mm 3mm DFN
Fe A Description
n
Wide Input Range: The LT 3686 is a current mode PWM step-down DC/DC
Operation from 3.6V to 37V converter with an internal 1.2A power switch, packaged in
Overvoltage Lockout Protects Circuit Through 10-lead 3mm 3mm DFN. The wide input range of 3.6V to
55V Transients 37V makes the LT3686 suitable for regulating power from
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Low Minimum On-Time: a wide variety of sources, including 24V industrial supplies
Converts 16V to 3.3V at 2MHz and automotive batteries. Its high maximum frequency al-
IN OUT
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1.2A Output Current lows the use of tiny inductors and capacitors, resulting in
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Adjustable Frequency: 300kHz to 2.5MHz a very small solution. Operating frequency above the AM
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Constant Switching Frequency at Light Loads band avoids interfering with radio reception, making the
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Tracking and Soft-Start LT3686 particularly suitable for automotive applications.
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Precision UVLO
Cycle-by-cycle current limit and DA current sense provide
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Short-Circuit Robust
protection against fault conditions. Soft-start and frequency
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I in Shutdown <1A
Q
foldback eliminate input current surge during start-up. An
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Internally Compensated
optional internal regulated active load at the output via
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10-Lead 3mm 3mm DFN Package
the BD pin keeps the LT3686 at full switching frequency
at light loads, resulting in low, predictable output ripple
Applic A
above the audio and AM bands. Internal compensation and
an internal boost diode reduce external component count.
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Automotive Systems
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
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Battery-Powered Equipment
of Linear Technology Corporation. All other trademarks are the property of their respective
n owners.
Wall Transformer Regulation
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Distributed Supply Regulation
t Al Applic A
3.3V Step-Down Converter 12V Efficiency (2.1MHz)
IN
90
V
IN
V BD
IN
6V TO 37V 80
3.3V
OUT
2.2F
EN/UVLO BOOST
0.22F
70
5V
OUT
LT3686 6.8H
60
SW V
MODE
OUT
3.3V
50
MBRM140
1.2A
SS
40
DA
31.6k
10nF RT
30
FB
GND
20
10k 22F
15.4k
10
3686 TA01a
0
0 200 400 600 800 1000 1200
(V 6V TO 16V AT 2.1MHz)
IN
LOAD CURRENT (mA)
3686 TA01b
3686fc
1
EFFICIENCY (%)
tion ypic
tions
turesLT3686
Absolute M A Mu M rA p in c F A
(Note 1)
TOP VIEW
Input Voltage (V ) ....................................................55V
IN
BOOST Voltage .........................................................55V V 1 10 SW
IN
BD 9 DA
2
BOOST Pin Above SW Pin .........................................25V
11
FB 3 BOOST
8
GND
FB Voltage ...................................................................6V
4
SS 7 MODE
EN/UVLO Voltage ......................................................55V
RT 5 6 EN/UVLO
BD Voltage ................................................................25V
DD PACKAGE
RT Voltage ..................................................................6V
10-LEAD (3mm 3mm) PLASTIC DFN
= 43C/W
SS Voltage ...............................................................2.5V
JA
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
MODE Voltage .............................................................6V
Operating Junction Temperature Range (Note 2)
LT3686E ............................................ 40C to 125C
LT3686I ............................................. 40C to 125C
LT3686H ............................................ 40C to 150C
Storage Temperature Range .................. 65C to 150C
o r Der i n F MA
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3686EDD#PBF LT3686EDD#TRPBF LDYC 10-Lead Plastic DFN 40C to 125C
LT3686IDD#PBF LT3686IDD#TRPBF LDYC 10-Lead Plastic DFN 40C to 125C
LT3686HDD#PBF LT3686HDD#TRPBF LDYC 10-Lead Plastic DFN 40C to 150C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: