LT3437
High Voltage 500mA, 200kHz
Step-Down Switching Regulator
with 100A Quiescent Current
FEATURES
DESCRIPTIO
Wide Input Range: 3.3V to 60V The LT 3437 is a 200kHz monolithic buck switching
Load Dump (Input Transient) Protection to 80V regulator that accepts input voltages up to 80V. A high
500mA Peak Switch Current efficiency 500mA, 0.8 switch is included on the die along
Burst Mode Operation: 100A Quiescent Current** with all the necessary oscillator, control and logic cir-
Low Shutdown Current: I < 1A cuitry. Current mode topology is used for fast transient
Q
Defeatable Burst Mode Operation response and good loop stability.
200kHz Switching Frequency
Innovative design techniques along with a new high volt-
Saturating Switch Design: 0.8 On-Resistance
age process achieve high efficiency over a wide input
Peak Switch Current Maintained Over
range. Efficiency is maintained over a wide output current
Full Duty Cycle Range*
range by employing Burst Mode operation at low currents,
1.25V Feedback Reference Voltage
utilizing the output to bias the internal circuitry, and by
Easily Synchronizable
using a supply boost capacitor to fully saturate the power
Soft-Start Capability
switch. Burst Mode operation can be defeated by a logic
Small 10-Pin Thermally Enhanced DFN Package
high signal on the SYNC pin which results in lower light
U
load ripple at the expense of light load efficiency. Patented
APPLICATIO S
circuitry maintains peak switch current over the full duty
High Voltage Power Conversion
cycle range.* Shutdown reduces input supply current to
14V and 42V Automotive Systems
less than 1A. External synchronization can be imple-
Industrial Power Systems
mented by driving the SYNC pin with logic-level inputs. A
Distributed Power Systems
single capacitor from the C pin to the output provides a
SS
Battery-Powered Systems
controlled output voltage ramp (soft-start).
Powered Ethernet
The LT3437 is available in a low profile (0.75mm) 3mm
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode
3mm 10-pin DFN package or a 16-Pin TSSOP Package,
is a registered trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. *Protected by U.S. Patents, including 6498466.
both with exposed pad leadframes for low thermal
**See Burst Mode Operation section for conditions.
resistance.
TYPICAL APPLICATIO
Input Voltage
14V to 3.3V Step-Down Converter with Supply Current vs Input Voltage Transient Response
100A No Load Quiescent Current
200
180
V
OUT
V
IN
V BOOST 3.3V
IN 160
4.5V TO 80V*
V
2.2F 100H 400mA IN
0.1F
BAS21
SHDN
140 20V/DIV
100V SW
CER
LT3437 0.1F
120
10MQ100N
V C
C SS V
100
IN
1500pF 330pF 0V
V
BIAS 80
V
165k
27pF OUT
25k
100F
60 20mV/DIV
SYNC FB 6.3V AC COUPLED
40
TANT 3437 TA03
I 250mA
OUT 50ms/DIV
GND 100k
20
LOAD DUMP COLD CRANK
0
3437 TA01
*FOR INPUT VOLTAGES ABOVE 60V RESTRICTIONS APPLY
0 10 20 30 40 50 60 70 80
INPUT VOLTAGE (V)
3437 TA02
3437fc
1
SUPPLY CURRENT (A)
U
ULT3437
ABSOLUTE AXI U RATI GS
(Note 1)
V , SHDN, BIAS, SW Operating ............................. 60V Operating Junction Temperature Range
IN
V , SHDN 100ms Transient, <15% Duty Cycle ....... 80V LT3437EDD (Note 2) ....................... 40C to 125C
IN
BOOST Pin Above SW ............................................ 35V LT3437IDD (Note 2) ........................ 40C to 125C
BOOST Pin Voltage Operating................................. 75V LT3437EFE (Note 2) ........................ 40C to 125C
BOOST Pin 100ms Transient, <15% Duty Cycle ...... 85V LT3437IFE (Note 2) ......................... 40C to 125C
SYNC, C , FB .......................................................... 6V LT3437HFE (Note 2) .......................... 40C to 140C
SS
Storage Temperature Range ................. 65C to 125C
DD Package ....................................... 65C to 125C
FE Package ........................................ 65C to 150C
UUW
PACKAGE/ORDER I FOR ATIO
TOP VIEW
NC 1 16 NC
TOP VIEW
SW 2 15 SHDN
NC 3
14 SYNC
SW 1 10 SHDN
V 4 13 NC
IN
V 2 9 SYNC
IN
17
BOOST 3 11 8 FB NC 5 12 FB
GND 4 7 V
C
BOOST 6 11 V
C
C 5 6 BIAS
SS
NC 7 10 BIAS
GND 8
9 C
SS
DD PACKAGE
10-LEAD (3mm 3mm) PLASTIC DFN
FE PACKAGE
= 45C/W, = 10C/W 16-LEAD PLASTIC TSSOP
JA JC(PAD)
= 45C/W, = 10C/W
EXPOSED PAD IS GND (PIN 11) JA JC(PAD)
MUST BE SOLDERED TO GND (PIN 4)
EXPOSED PAD IS GND (PIN 17)
MUST BE SOLDERED TO GND (PIN 8)
ORDER PART NUMBER DD PART MARKING ORDER PART NUMBER FE PART MARKING
LT3437EDD LBDJ LT3437EFE 3437EFE
LT3437IDD LBDK LT3437IFE 3437IFE
LT3437HFE 3437HFE
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: