LT3973_15 Datasheet, PDF (1/24 Pages) Linear Technology – 42V, 750mA Step-Down Regulator with 2.5A Quiescent Current and Integrated Diodes

FEATURES
nn _{Ultralow Quiescent Current}
nn _{2.5µA IQ at 12VIN to 3.3VOUT}
nn _{Low Ripple Burst Mode}^® _Operation
nn _{Output Ripple < 10mVP-P}
nn _{Wide Input Voltage Range: 4.2V to 42V Operating}
nn _{Adjustable Switching Frequency: 200kHz to 2.2MHz}
nn _{Integrated Boost and Catch Diodes}
nn _{750mA Output Current}
nn _{Excellent Start-Up and Dropout Performance}
nn _{Fixed Output Voltages: 3.3V, 5V}
nn _{1.9µA IQ at 12VIN}
nn _{Accurate Programmable Undervoltage Lockout}
nn _{Low Shutdown Current: IQ = 0.75µA}
nn _{Internal Catch Diode Current Limit}
nn _{Power Good Flag}
nn _{Thermal Shutdown}
nn _{Small, Thermally Enhanced 10-Lead MSOP and}
(3mm × 3mm) DFN Packages
APPLICATIONS
nn _{Automotive Battery Regulation}
nn _{Power for Portable Products}
nn _{Industrial Supplies}
nn _{Gate Drive Bias}
LT3973/LT3973-3.3/LT3973-5
42V, 750mA Step-Down
Regulator with 2.5µA
Quiescent Current and
Integrated Diodes
DESCRIPTION
The LT^®3973 is an adjustable frequency monolithic buck
switching regulator that accepts a wide input voltage range
up to 42V, and consumes only 2.5µA of quiescent current.
A high efficiency switch is included on the die along with
the catch diode, boost diode, and the necessary oscillator,
control and logic circuitry. Low ripple Burst Mode operation
maintains high efficiency at low output currents while keep-
ing the output ripple below 10mV in a typical application.
A minimum dropout voltage of 530mV is maintained when
the input voltage drops below the programmed output volt-
age, such as during automotive cold crank. Current mode
topology is used for fast transient response and good loop
stability. A catch diode current limit provides protection
against shorted outputs and overvoltage conditions, with
thermal shutdown providing additional fault protection. An
accurate programmable undervoltage lockout feature is
available, producing a low shutdown current of 0.75µA.
A power good flag signals when V_OUT reaches 90% of
the programmed output voltage. The LT3973 is available
in small, thermally enhanced 10-lead MSOP and 3mm ×
3mm DFN packages.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
5V Step-Down Converter
V_IN
5.6V TO 42V
C1
4.7µF
OFF ON
215k
V_IN BOOST
LT3973
EN/UVLO SW
PG
BD
OUT
RT
FB
GND
C3
0.47µF
L1
15µH
15pF 1M
316k
V_OUT
5V
750mA
C2
22µF
f = 600kHz
3973 TA01a
Efficiency
90
V_IN = 12V
1000
80
100
70
10
60
1
50
0.1
40
0.01
0.01
0.1
1
10
100
LOAD CURRENT (mA)
3973 TA01b
For more information www.linear.com/LT3973
3973fb
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