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LT3972IMSE#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
LT3972
1
3972fa
TYPICAL APPLICATION
33V, 3.5A, 2.4MHz
Step-Down Switching Regulator
with 75µA Quiescent Current
The LT
®
3972 is an adjustable frequency (200kHz to 2.4MHz)
monolithic buck switching regulator that accepts input
voltages up to 33V (62V maximum). A high effi ciency
95mΩ switch is included on the die along with a boost
Schottky diode and the necessary oscillator, control and
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Low ripple
Burst Mode operation maintains high effi ciency at low
output currents while keeping output ripple below 15mV
in a typical application. In addition, the LT3972 can fur-
ther enhance low output current effi ciency by drawing
bias current from the output when V
OUT
is above 3V.
Shutdown reduces input supply current to less than 1μA
while a resistor and capacitor on the RUN/SS pin provide a
controlled output voltage ramp (soft-start). A power good
fl ag signals when V
OUT
reaches 91% of the programmed
output voltage. The LT3972 is available in 10-pin MSOP
and 3mm × 3mm DFN packages with exposed pads for
low thermal resistance.
■
Automotive Battery Regulation
■
Distributed Supply Regulation
■
Industrial Supplies
■
Wall Transformer Regulation
■
Wide Input Range:
Operation from 3.6V to 33V
Overvoltage Lockout Protects Circuits
Through 62V Transients
■
3.5A Maximum Output Current
■
Low Ripple (<15mV
P-P
) Burst Mode
®
Operation:
I
Q
= 75μA at 12V
IN
to 3.3V
OUT
■
Adjustable Switching Frequency: 200kHz to 2.4MHz
■
Low Shutdown Current: I
Q
< 1μA
■
Integrated Boost Diode
■
Synchronizable Between 250kHz to 2MHz
■
Power Good Flag
■
Saturating Switch Design: 95mΩ On-Resistance
■
Output Voltage: 0.79V to 30V
■
Thermal Protection
■
Soft-Start Capability
■
Small 10-Pin Thermally Enhanced MSOP and
(3mm × 3mm) DFN Packages
5V Step-Down Converter
SW
FB
V
C
PG
RT
V
IN
BD
V
IN
6.3V TO 33V
TRANSIENT
TO 62V
V
OUT
5V
3.5A
10μF
0.47μF
680pF
47μF
100k
15k
63.4k
4.7μH
536k
GND
OFF ON
LT3972
3972 TA01
RUN/SS BOOST
SYNC
Effi ciency
OUTPUT CURRENT (A)
0 0.5
50
EFFICIENCY (%)
70
100
1
2
2.5
3972 TA01a
60
90
80
1.5
3
3.5
V
IN
= 12V
V
IN
= 30V
V
OUT
= 5V
L = 4.7μH
f = 600kHz
V
IN
= 24V
DESCRIPTION
FEATURES
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.
LT3972
2
3972fa
ELECTRICAL CHARACTERISTICS
V
IN
, RUN/SS Voltage (Note 5) ...................................62V
BOOST Pin Voltage ...................................................56V
BOOST Pin Above SW Pin .........................................30V
FB, RT, V
C
Voltage .......................................................5V
PG, BD, SYNC Voltage ..............................................30V
(Note 1)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage
●
3 3.6 V
V
IN
Overvoltage Lockout
●
33 35 37 V
Quiescent Current from V
IN
V
RUN/SS
= 0.2V 0.01 0.5 μA
V
BD
= 3V, Not Switching
●
30 65 μA
V
BD
= 0, Not Switching 120 160 μA
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 10V, V
RUN/SS
= 10V, V
BOOST
= 15V, V
BD
= 3.3V unless otherwise
noted. (Note 2)
Operating Junction Temperature Range (Note 2)
LT3972E .............................................–40°C to 125°C
LT3972I ..............................................–40°C to 125°C
LT3972H ............................................– 40°C to 150°C
Storage Temperature Range ...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
(MSE Only) ....................................................... 300°C
TOP VIEW
DD PACKAGE
10-LEAD (3mm s 3mm) PLASTIC DFN
10
9
6
7
8
4
5
3
11
2
1
RT
V
C
FB
PG
SYNC
BD
BOOST
SW
V
IN
RUN/SS
θ
JA
= 45°C/W, θ
JC
= 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
1
2
3
4
5
BD
BOOST
SW
V
IN
RUN/SS
10
9
8
7
6
RT
V
C
FB
PG
SYNC
TOP VIEW
MSE PACKAGE
10-LEAD PLASTIC MSOP
11
θ
JA
= 45°C/W, θ
JC
= 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
PIN CONFIGURATION
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3972EDD#PBF LT3972EDD#TRPBF LDXR
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3972IDD#PBF LT3972IDD#TRPBF LDXR
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3972EMSE#PBF LT3972EMSE#TRPBF LTDXS 10-Lead Plastic MSOP –40°C to 125°C
LT3972IMSE#PBF LT3972IMSE#TRPBF LTDXS 10-Lead Plastic MSOP –40°C to 125°C
LT3972HMSE#PBF LT3972HMSE#TRPBF LTDXS 10-Lead Plastic MSOP –40°C to 150°C
Consult LTC Marketing for parts specifi
ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
Consult L
TC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/
ABSOLUTE MAXIMUM RATINGS
LT3972
3
3972fa
PARAMETER CONDITIONS MIN TYP MAX UNITS
Quiescent Current from BD V
RUN/SS
= 0.2V 0.01 0.5 μA
V
BD
= 3V, Not Switching
●
90 130 μA
V
BD
= 0, Not Switching 15 μA
Minimum Bias Voltage (BD Pin) 2.7 3 V
Feedback Voltage
●
780
775
790
790
800
805
mV
mV
FB Pin Bias Current (Note 3) V
FB
= 0.8V, V
C
= 1.2V
●
10 40 nA
FB Voltage Line Regulation 4V < V
IN
< 33V 0.002 0.01 %/V
Error Amp g
m
500 μmho
Error Amp Gain 2000
V
C
Source Current 60 μA
V
C
Sink Current 60 μA
V
C
Pin to Switch Current Gain 5.3 A/V
V
C
Clamp Voltage 2V
Switching Frequency R
T
= 8.66k
R
T
= 29.4k
R
T
= 187k
2.2
1.0
200
2.45
1.1
230
2.7
1.25
260
MHz
MHz
kHz
Minimum Switch Off-Time
●
60 150 ns
Switch Current Limit Duty Cycle = 5% 4.6 5.4 6.2 A
Switch V
CESAT
I
SW
= 3.5A 335 mV
Boost Schottky Reverse Leakage V
BD
= 0V 0.02 2 μA
Minimum Boost Voltage (Note 4)
●
1.5 2 V
BOOST Pin Current I
SW
= 1A 35 50 mA
RUN/SS Pin Current V
RUN/SS
= 2.5V 5 8 μA
RUN/SS Input Voltage High 2.5 V
RUN/SS Input Voltage Low 0.2 V
PG Threshold Offset from Feedback Voltage V
FB
Rising 65 mV
PG Hysteresis 10 mV
PG Leakage
V
PG
= 5V 0.1 1 μA
PG Sink Current V
PG
= 0.4V
●
200 800 μA
SYNC Low Threshold 0.5 V
SYNC High Threshold 0.7 V
SYNC Pin Bias Current V
SYNC
= 0V 0.1 μA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3972E is guaranteed to meet performance specifi cations
from 0°C to 125°C. Specifi cations over the –40°C to 125°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3972I specifi cations are
guaranteed over the –40°C to 125°C temperature range. The LT3972H
specifi cations are guaranteed over the –40°C to 150°C operating
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 3: Bias current fl ows out of the FB pin.
Note 4: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 5: Absolute Maximum at V
IN
and RUN/SS pins is 62V for non-
repetitive 1 minute transients, and 40V for continuous operation.
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 10V, V
RUN/SS
= 10V, V
BOOST
= 15V, V
BD
= 3.3V unless otherwise
noted. (Note 2)
ELECTRICAL CHARACTERISTICS
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LT3972IMSE#PBF

Mfr. #:
Buy LT3972IMSE#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 36V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75uA Quiescent Current
Lifecycle:
New from this manufacturer.
Delivery:
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