LT3970/LT3970-3.3/LT3970-5
40V, 350mA Step-Down
Regulator with 2.5µA
Quiescent Current and
Integrated Diodes
FEATURES
DESCRIPTION
Low Ripple Burst Mode® Operation
The LT®3970 is an adjustable frequency monolithic buck
switching regulator that accepts a wide input voltage
range up to 40V, 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 neces-
saryoscillator, controlandlogiccircuitry. LowrippleBurst
Mode operation maintains high efficiency at low output
currents while keeping the output ripple below 5mV in a
typical application. 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. An enable pin with accurate
threshold is available, producing a low shutdown current
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2.5μA I at 12V to 3.3V
Q
IN
OUT
Output Ripple < 5mV
P-P
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Wide Input Voltage Range: 4.2V to 40V Operating
Adjustable Switching Frequency: 200kHz to 2.2MHz
Integrated Boost and Catch Diodes
350mA Output Current
Fixed Output Voltages: 3.3V, 5V
1.8μA I at 12V
Q
IN
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Accurate 1V Enable Pin Threshold
Low Shutdown Current: I = 0.7μA
Q
Internal Sense Limits Catch Diode Current
Power Good Flag
Output Voltage: 1.21V to 25V
of 0.7μA. A power good flag signals when V
reaches
OUT
Internal Compensation
90% of the programmed output voltage. The LT3970 is
available in small 10-pin MSOP and 3mm × 2mm DFN
packages.
Small 10-Pin MSOP and (3mm × 2mm) DFN Packages
APPLICATIONS
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
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Automotive Battery Regulation
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Power for Portable Products
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Industrial Supplies
TYPICAL APPLICATION
5V Step-Down Converter
Efficiency
90
1000
100
10
V
= 12V
V
IN
IN
6V TO 40V
0.22μF
80
70
60
50
40
V
BOOST
LT3970
IN
22μH
22pF
V
OUT
5V
OFF ON
EN
PG
SW
BD
350mA
1M
1
RT
FB
22μF
2.2μF
GND
316k
226k
f = 600kHz
0.1
0.01
3490 TA01a
0.01
0.1
1
10
100
LOAD CURRENT (mA)
3970 TA01b
3970fa
1