LT3975
42V, 2.5A, 2MHz Step-Down
Switching Regulator with
2.7A Quiescent Current
FEATURES DESCRIPTION
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Ultralow Quiescent Current:
The LT 3975 is an adjustable frequency monolithic buck
2.7A I at 12V to 3.3V
switching regulator that accepts a wide input voltage range
Q IN OUT
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Low Ripple Burst Mode Operation
up to 42V. Low quiescent current design consumes only
Output Ripple < 15mV
2.7A of supply current while regulating with no load. Low
P-P
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Wide Input Range: Operation from 4.3V to 42V
ripple Burst Mode operation maintains high efficiency at
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2.5A Maximum Output Current
low output currents while keeping the output ripple below
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Excellent Start-Up and Dropout Performance
15mV in a typical application. The LT3975 can supply up
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Adjustable Switching Frequency: 200kHz to 2MHz
to 2.5A of load current and has current limit foldback to
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Synchronizable Between 250kHz to 2MHz
limit power dissipation during short circuit. A low dropout
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Accurate Programmable Undervoltage Lockout
voltage of 500mV is maintained when the input voltage
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Low Shutdown Current: I = 700nA
drops below the programmed output voltage, such as
Q
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Power Good Flag
during automotive cold crank.
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Soft-Start Capability
An internally compensated current mode topology is used
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Thermal Shutdown Protection
for fast transient response and good loop stability. A high
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Current Limit Foldback with Soft-Start Override
efficiency 75m switch is included on the die along with a
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Saturating Switch Design: 75m On Resistance
boost Schottky diode and the necessary oscillator, control,
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Small, Thermally Enhanced 16-Lead MSOP Package
and logic circuitry. An accurate 1.02V threshold enable pin
can be driven directly from a microcontroller or used as a
APPLICATIONS
programmable undervoltage lockout. A capacitor on the
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Automotive Battery Regulation
SS pin provides a controlled inrush current (soft-start).
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Portable Products
A power good flag signals when V reaches 91.6% of
OUT
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Industrial Supplies
the programmed output voltage. The LT3975 is available
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
in a small 16-lead MSOP package with exposed pad for
of Linear Technology Corporation. All other trademarks are the property of their respective
low thermal resistance.
owners.
TYPICAL APPLICATION
No-Load Supply Current
4.5
3.3V Step-Down Converter
IN REGULATION
V
IN
4.0
4.3V TO 42V
V
IN
3.5
OFF ON EN BOOST
0.47F 3.3H
3.0
PG SW
10F PDS560
LT3975
2.5
SS OUT
2.0
1M V
OUT
3.3V
RT FB
1.5
10pF 2.5A
SYNC GND
10nF
47F
78.7k 576k 1.0
1210
0 5 10 15 20 25 30 35 40 45
3975 TA01a
INPUT VOLTAGE (V)
f = 600kHz
3975 TA01b
3975f
1
INPUT CURRENT (A)LT3975
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
TOP VIEW
V , EN Voltage (Note 3) ...........................................42V
IN
FB 1 16 SYNC
2
BOOST Pin Voltage ...................................................55V SS 15 PG
OUT 3 14 RT
BOOST Pin Above SW Pin .........................................30V 4 17
BOOST 13 EN
SW 5 GND 12 V
IN
FB, RT, SYNC, SS Voltage ...........................................6V
6
SW 11 V
IN
SW 7 10 V
IN
PG Voltage ................................................................30V
8
NC 9 NC
OUT Voltage ..............................................................16V
MSE PACKAGE
16-LEAD PLASTIC MSOP
Operating Junction Temperature Range (Note 2)
= 40C/W
JA
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
LT3975E ............................................. 40C to 125C
LT3975I.............................................. 40C to 125C
LT3975H ............................................ 40C to 150C
Storage Temperature Range .................. 65C to 150C
Lead Temperature (Soldering, 10 sec) ...................300C
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3975EMSE#PBF LT3975EMSE#TRPBF 3975 16-Lead Plastic MSOP 40C to 125C
LT3975IMSE#PBF LT3975IMSE#TRPBF 3975 16-Lead Plastic MSOP 40C to 125C
LT3975HMSE#PBF LT3975HMSE#TRPBF 3975 16-Lead Plastic MSOP 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: