POWER LOSS (mW)
LT3973/LT3973-3.3/LT3973-5
42V, 750mA Step-Down
Regulator with 2.5A
Quiescent Current and
Integrated Diodes
FEATURES DESCRIPTION
n
Ultralow Quiescent Current The LT 3973 is an adjustable frequency monolithic buck
n
2.5A I at 12V to 3.3V switching regulator that accepts a wide input voltage range
Q IN OUT
n
up to 42V, and consumes only 2.5A of quiescent current.
Low Ripple Burst Mode Operation
n
A high efficiency switch is included on the die along with
Output Ripple < 10mV
P-P
n
the catch diode, boost diode, and the necessary oscillator,
Wide Input Voltage Range: 4.2V to 42V Operating
n control and logic circuitry. Low ripple Burst Mode operation
Adjustable Switching Frequency: 200kHz to 2.2MHz
n maintains high efficiency at low output currents while keep-
Integrated Boost and Catch Diodes
n ing the output ripple below 10mV in a typical application.
750mA Output Current
A minimum dropout voltage of 530mV is maintained when
n
Excellent Start-Up and Dropout Performance
the input voltage drops below the programmed output volt-
n
Fixed Output Voltages: 3.3V, 5V
age, such as during automotive cold crank. Current mode
n
1.9A I at 12V
Q IN
topology is used for fast transient response and good loop
n
Accurate Programmable Undervoltage Lockout
stability. A catch diode current limit provides protection
n
Low Shutdown Current: I = 0.75A
Q
against shorted outputs and overvoltage conditions, with
n
Internal Catch Diode Current Limit
thermal shutdown providing additional fault protection. An
n
Power Good Flag
accurate programmable undervoltage lockout feature is
n
Thermal Shutdown
available, producing a low shutdown current of 0.75A.
n
Small, Thermally Enhanced 10-Lead MSOP and
A power good flag signals when V reaches 90% of
OUT
(3mm 3mm) DFN Packages
the programmed output voltage. The LT3973 is available
in small, thermally enhanced 10-lead MSOP and 3mm
APPLICATIONS
3mm DFN packages.
n
Automotive Battery Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Power for Portable Products of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
n
Industrial Supplies
n
Gate Drive Bias
Efficiency
TYPICAL APPLICATION
90 1000
V = 12V
IN
5V Step-Down Converter
V
IN 80 100
5.6V TO 42V
C3
0.47F
V BOOST
IN
70 10
L1
LT3973
15H
V
OUT
OFF ON EN/UVLO SW 5V
60 1
750mA
PG BD
OUT 15pF
1M
C1 C2
RT FB
50 0.1
4.7F 22F
GND
215k
316k
40 0.01
3973 TA01a
f = 600kHz
0.01 0.1 1 10 100
LOAD CURRENT (mA)
3973 TA01b
3973fb
1
For more information www.linear.com/LT3973
EFFICIENCY (%)LT3973/LT3973-3.3/LT3973-5
ABSOLUTE MAXIMUM RATINGS (Note 1)
V , EN/UVLO Voltage ...............................................42V Operating Junction Temperature Range (Note 2)
IN
BOOST Pin Voltage ...................................................55V LT3973E/LT3973E-X .......................... 40C to 125C
BOOST Pin Above SW Pin .........................................25V LT3973I/LT3973I-X ............................ 40C to 125C
FB/V , RT, PG Voltage .............................................6V LT3973H/LT3973H-X ......................... 40C to 150C
OUT
BD Voltage ................................................................25V Storage Temperature Range .................. 65C to 150C
OUT Voltage ..............................................................14V Lead Temperature (Soldering, 10 sec)
MSE Only ..........................................................300C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
*FB/V 1 10 RT
OUT
*FB/V 1 10 RT
OUT
OUT 9 PG
2
OUT 2 9 PG
11
11
EN/UVLO 3 8 BD EN/UVLO 3 8 BD
GND
GND
V 4 7 BOOST
IN
V 4 7 BOOST
IN
GND 5 6 SW
GND 5 6 SW
MSE PACKAGE
10-LEAD PLASTIC MSOP
DD PACKAGE
= 45C/W, = 10C/W
JA JC
10-LEAD (3mm 3mm) PLASTIC DFN
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
= 40C/W, = 5C/W
JA JC
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
* FB for LT3973, V for LT3973-3.3, LT3973-5.
OUT
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3973EDD#PBF LT3973EDD#TRPBF LGCH 10-Lead (3mm 3mm) Plastic DFN 40C to 125C
LT3973IDD#PBF LT3973IDD#TRPBF LGCH 10-Lead (3mm 3mm) Plastic DFN 40C to 125C
LT3973HDD#PBF LT3973HDD#TRPBF LGCH 10-Lead (3mm 3mm) Plastic DFN 40C to 150C
LT3973EMSE#PBF LT3973EMSE#TRPBF LTFYS 10-Lead Plastic MSOP 40C to 125C
LT3973IMSE#PBF LT3973IMSE#TRPBF LTFYS 10-Lead Plastic MSOP 40C to 125C
LT3973HMSE#PBF LT3973HMSE#TRPBF LTFYS 10-Lead Plastic MSOP 40C to 150C
LT3973EMSE-3.3#PBF LT3973EMSE-3.3#TRPBF LTGGB 10-Lead Plastic MSOP 40C to 125C
LT3973IMSE-3.3#PBF LT3973IMSE-3.3#TRPBF LTGGB 10-Lead Plastic MSOP 40C to 125C
LT3973HMSE-3.3#PBF LT3973HMSE-3.3#TRPBF LTGGB 10-Lead Plastic MSOP 40C to 150C
LT3973EDD-3.3#PBF LT3973EDD-3.3#TRPBF LGGC 10-Lead (3mm 3mm) Plastic DFN 40C to 125C
LT3973IDD-3.3#PBF LT3973IDD-3.3#TRPBF LGGC 10-Lead (3mm 3mm) Plastic DFN 40C to 125C
LT3973HDD-3.3#PBF LT3973HDD-3.3#TRPBF LGGC 10-Lead (3mm 3mm) Plastic DFN 40C to 150C
LT3973EMSE-5#PBF LT3973EMSE-5#TRPBF LTGGD 10-Lead Plastic MSOP 40C to 125C
LT3973IMSE-5#PBF LT3973IMSE-5#TRPBF LTGGD 10-Lead Plastic MSOP 40C to 125C
LT3973HMSE-5#PBF LT3973HMSE-5#TRPBF LTGGD 10-Lead Plastic MSOP 40C to 150C
3973fb
2
For more information www.linear.com/LT3973