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Linear Technology Electronic Components Datasheet

LT3971A Datasheet

Step-Down Regulator

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FEATURES
n Ultralow Quiescent Current:
2.8μA IQ Regulating 12VIN to 3.3VOUT
n Fixed Output Voltages: 5V
2.2μA IQ Regulating 12VIN to 5VOUT
n Low Ripple Burst Mode® Operation:
Output Ripple < 15mVP-P
n Wide Input Voltage Range: 4.3V to 38V
n 1.3A Maximum Output Current
n Adjustable Switching Frequency: 200kHz to 2MHz
n Synchronizable Between 250kHz to 2MHz
n Fast Transient Response
n Accurate 1V Enable Pin Threshold
n Low Shutdown Current: IQ = 700nA
n Power Good Flag
n Soft-Start Capability
n Internal Compensation
n Output Voltage: 1.19V to 30V
n Small Thermally Enhanced 10-Lead MSOP Package
APPLICATIONS
n USB VBUS Regulation
n Automotive Battery Regulation
n Power for Portable Products
n Industrial Supplies
LT3971A/LT3971A-5
38V, 1.3A, 2MHz
Step-Down Regulator with
2.2µA Quiescent Current
DESCRIPTION
The LT®3971A is an adjustable frequency monolithic buck
switching regulator that accepts a wide input voltage range
up to 38V. Low quiescent current design consumes only
2.8μA of supply current while regulating with no load. Low
ripple Burst Mode operation maintains high efficiency at
low output currents while keeping the output ripple below
15mV in a typical application. An internally compensated
current mode topology is used for fast transient response
and good loop stability. A high efficiency 0.33Ω switch
is included on the die along with a boost Schottky diode
and the necessary oscillator, control and logic circuitry.
An accurate 1V threshold enable pin can be used to shut
down the LT3971A, reducing the input supply current to
700nA. A capacitor on the SS pin provides a controlled
inrush current (soft-start). A power good flag signals when
VOUT reaches 91% of the programmed output voltage. The
LT3971A is available in a small 10-lead MSOP package
with an exposed pad for low thermal resistance.
The LT3971A and LT3971A-5 have a more accurate ref-
erence voltage compared to the LT3971 and LT3971-5.
The LT3971A-5 also has specified VOUT pin current and
ABSMAX current. These characteristics are important for
USB applications.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
5.15V Step-Down Converter for USB Applications
VIN
6.3V TO 38V
OFF ON EN
VIN BOOST
4.7μF
PG
SW
SS LT3971A-5
RT
BD
118k
SYNC GND VOUT
f = 400kHz
0.47μF 10μH
20k, 1%
715k
47μF
1%
3971 TA01a
VOUT
5.15V
1.3A
No Load Supply Current
3.0
OUTPUT IN REGULATION
2.5
LT3971A-5
2.0
1.5
1.0
5
10 15 20 25 30 35
INPUT VOLTAGE (V)
3971A TA01b
3971af
1


Linear Technology Electronic Components Datasheet

LT3971A Datasheet

Step-Down Regulator

No Preview Available !

LT3971A/LT3971A-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, EN Voltage .........................................................38V
BOOST Pin Voltage ...................................................55V
BOOST Pin Above SW Pin.........................................30V
FB, RT, SYNC, SS Voltage ...........................................6V
PG, BD Voltage .........................................................30V
VOUT Pin Current....................................................–2mA
Operating Junction Temperature Range (Note 2)
LT3971AI/LT3971AI-5........................ –40°C to 125°C
Storage Temperature Range .............. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
(MSE Only) ....................................................... 300°C
PIN CONFIGURATION
LT3971A
BD 1
BOOST 2
SW 3
VIN 4
EN 5
TOP VIEW
11
GND
10 SYNC
9 PG
8 RT
7 SS
6 FB
MSE PACKAGE
10-LEAD PLASTIC MSOP
θJA = 45°C, θJC = 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
LT3971A-5
TOP VIEW
BD 1
10 SYNC
BOOST 2
SW 3
VIN 4
11
GND
9 PG
8 RT
7 SS
EN 5
6 VOUT
MSE PACKAGE
10-LEAD PLASTIC MSOP
θJA = 45°C, θJC = 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3971AIMSE#PBF
LT3971AIMSE#TRPBF LTGFQ
10-Lead Plastic MSOP
–40°C to 125°C
LT3971AIMSE-5#PBF
LT3971AIMSE-5#TRPBF LTGFR
10-Lead Plastic MSOP
–40°C to 125°C
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: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VEN = 12V, VBD = 3.3V unless otherwise noted. (Note 2)
PARAMETER
Minimum Input Voltage
Quiescent Current from VIN
LT3971A FB Pin Current
Internal Feedback Resistor Divider (LT3971A-5)
CONDITIONS
(Note 4)
VEN Low
VEN High, VSYNC Low
VEN High, VSYNC Low
VFB = 1.19V
MIN
TYP
MAX
l
4
4.3
0.7
1.2
1.7
2.7
l
4.5
l
0.1
12
10
UNITS
V
μA
μA
μA
nA
3971af
2


Part Number LT3971A
Description Step-Down Regulator
Maker Linear
PDF Download

LT3971A Datasheet PDF






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