LT3970-5 Datasheet PDF - Linear Technology

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LT3970-5
Linear Technology

Part Number LT3970-5
Description 350mA Step-Down Regulator
Page 22 Pages


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FEATURES
n Low Ripple Burst Mode® Operation
2.5μA IQ at 12VIN to 3.3VOUT
Output Ripple < 5mVP-P
n Wide Input Voltage Range: 4.2V to 40V Operating
n Adjustable Switching Frequency: 200kHz to 2.2MHz
n Integrated Boost and Catch Diodes
n 350mA Output Current
n Fixed Output Voltages: 3.3V, 5V
1.8μA IQ at 12VIN
n Accurate 1V Enable Pin Threshold
n Low Shutdown Current: IQ = 0.7μA
n Internal Sense Limits Catch Diode Current
n Power Good Flag
n Output Voltage: 1.21V to 25V
n Internal Compensation
n Small 10-Pin MSOP and (3mm × 2mm) DFN Packages
APPLICATIONS
n Automotive Battery Regulation
n Power for Portable Products
n Industrial Supplies
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LT3970/LT3970-3.3/LT3970-5
40V, 350mA Step-Down
Regulator with 2.5µA
Quiescent Current and
Integrated Diodes
DESCRIPTION
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-
sary oscillator, control and logic circuitry. Low ripple Burst
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
of 0.7μA. A power good flag signals when VOUT reaches
90% of the programmed output voltage. The LT3970 is
available in small 10-pin MSOP and 3mm × 2mm DFN
packages.
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.
TYPICAL APPLICATION
5V Step-Down Converter
VIN
6V TO 40V
OFF ON
VIN BOOST
LT3970
EN SW
PG BD
2.2μF
RT FB
226k
GND
f = 600kHz
0.22μF
22μH
22pF
1M
316k
VOUT
5V
350mA
22μF
3490 TA01a
90
VIN = 12V
80
Efficiency
1000
100
70 10
60 1
50 0.1
40
0.01
0.1 1 10
LOAD CURRENT (mA)
0.01
100
3970 TA01b
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LT3970/LT3970-3.3/LT3970-5
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ABSOLUTE MAXIMUM RATINGS (Note 1)
VIN, EN Voltage .........................................................40V
BOOST Pin Voltage ...................................................55V
BOOST Pin Above SW Pin.........................................30V
FB/VOUT, RT Voltage ....................................................6V
PG, BD Voltage .........................................................30V
Operating Junction Temperature Range (Note 2)
LT3970E/LT3970E-X........................... –40°C to 125°C
LT3970I/LT3970I-X ............................ –40°C to 125°C
LT3970H-X......................................... –40°C to 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MS Only............................................................ 300°C
PIN CONFIGURATION
TOP VIEW
*FB/VOUT 1
EN 2
VIN 3
GND 4
GND 5
10 RT
9 PG
11
GND
8 BD
7 BOOST
6 SW
DDB PACKAGE
10-LEAD (3mm × 2mm) PLASTIC DFN
θJA = 76°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
*FB for LT3970, VOUT for LT3970-3.3, LT3970-5.
*FB/VOUT 1
EN 2
VIN 3
GND 4
GND 5
TOP VIEW
10 RT
9 PG
8 BD
7 BOOST
6 SW
MS PACKAGE
10-LEAD PLASTIC MSOP
θJA = 100°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3970EDDB#PBF
LT3970EDDB#TRPBF
LFCZ
10-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3970IDDB#PBF
LT3970IDDB#TRPBF
LFCZ
10-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3970EMS#PBF
LT3970EMS#TRPBF
LTFDB
10-Lead Plastic MSOP
–40°C to 125°C
LT3970IMS#PBF
LT3970IMS#TRPBF
LTFDB
10-Lead Plastic MSOP
–40°C to 125°C
LT3970EDDB-3.3#PBF LT3970EDDB-3.3#TRPBF LFQH
10-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3970IDDB-3.3#PBF
LT3970IDDB-3.3#TRPBF LFQH
10-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3970EMS-3.3#PBF
LT3970EMS-3.3#TRPBF LTFQG
10-Lead Plastic MSOP
–40°C to 125°C
LT3970IMS-3.3#PBF
LT3970IMS-3.3#TRPBF LTFQG
10-Lead Plastic MSOP
–40°C to 125°C
LT3970HMS-3.3#PBF
LT3970HMS-3.3#TRPBF LTFQG
10-Lead Plastic MSOP
–40°C to 150°C
LT3970EDDB-5#PBF
LT3970EDDB-5#TRPBF
LFQF
10-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3970IDDB-5#PBF
LT3970IDDB-5#TRPBF
LFQF
10-Lead (3mm × 2mm) Plastic DFN
–40°C to 125°C
LT3970EMS-5#PBF
LT3970EMS-5#TRPBF
LTFQD
10-Lead Plastic MSOP
–40°C to 125°C
LT3970IMS-5#PBF
LT3970IMS-5#TRPBF
LTFQD
10-Lead Plastic MSOP
–40°C to 125°C
LT3970HMS-5#PBF
LT3970HMS-5#TRPBF
LTFQD
10-Lead Plastic MSOP
–40°C to 150°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/
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LT3970/LT3970-3.3/LT3970-5
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VBD = 3.3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN TYP MAX
Minimum Input Voltage
l 4 4.2
Quiescent Current from VIN
LT3970 Feedback Voltage
VEN Low
VEN High
VEN High, –40°C to 125°C
VEN High, –40°C to 150°C
0.7 1.2
1.7 2.7
l 3.5
l4
1.195 1.21 1.225
l 1.185 1.21 1.235
LT3970-3.3 Output Voltage
–40°C to 125°C
–40°C to 150°C
3.26 3.3 3.34
l 3.234 3.3 3.366
l 3.217 3.3 3.366
LT3970-5 Output Voltage
–40°C to 125°C
–40°C to 150°C
4.94
l 4.9
l 4.875
5
5
5
5.06
5.1
5.1
LT3970 FB Pin Bias Current (Note 3)
FB/Output Voltage Line Regulation
Switching Frequency
Switch Current Limit
Catch Schottky Current Limit
VFB = 1.21V
4.2V < VIN < 40V
RT = 41.2k, VIN = 6V
RT = 158k, VIN = 6V
RT = 768k, VIN = 6V
VIN = 5V, VFB = 0V
VIN = 5V
l
1.76
640
160
535
350
0.1
0.0002
2.25
800
200
700
400
20
0.01
2.64
960
240
865
500
Switch VCESAT
Switch Leakage Current
ISW = 200mA
175
0.05 2
Catch Schottky Forward Voltage
Catch Schottky Reverse Leakage
Boost Schottky Forward Voltage
Boost Schottky Reverse Leakage
Minimum Boost Voltage (Note 4)
BOOST Pin Current
EN Pin Current
LT3970 EN Voltage Threshold
LT3970-X EN Voltage Threshold
EN Voltage Hysteresis
ISCH = 100mA, VIN = VBD = NC
VSW = 12V
ISCH = 50mA, VIN = NC, VBOOST = 0V
VREVERSE = 12V
VIN = 5V
ISW = 200mA, VBOOST = 15V
VEN = 12V
EN Rising, VIN ≥ 4.2V
EN Rising, VIN ≥ 4.2V
650
0.05 2
875
0.02 2
l 1.4 1.8
7 10
1 30
l 0.94 1 1.06
l 0.93 1 1.07
30
LT3970 PG Threshold Offset from Feedback Voltage VFB Rising
LT3970 PG Hysteresis
80 120 160
12
LT3970-X PG Threshold Offset from Output Voltage VFB Rising
LT3970-X PG Hysteresis as % of Output Voltage
6.5 10 13.5
1.0
PG Leakage
PG Sink Current
VPG = 3V
VPG = 0.4V
l 30
0.01
80
1
Minimum Switch On-Time
90
Minimum Switch Off-Time
VIN = 10V
l 100 160
UNITS
V
μA
μA
μA
μA
V
V
V
V
V
V
V
V
nA
%/V
MHz
kHz
kHz
mA
mA
mV
μA
mV
μA
mV
μA
V
mA
nA
V
V
mV
mV
mV
%
%
μA
μA
ns
ns
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LT3970/LT3970-3.3/LT3970-5
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ELECTRICAL CHARACTERISTICS
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 LT3970E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization, and correlation with statistical process controls. The
LT3970I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT3970H is guaranteed over the full –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures greater than 125°C.
Note 3: Bias current flows into the FB pin.
Note 4: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Efficiency, VOUT = 3.3V
90
80
VIN = 24V
70
VIN = 12V
60 VIN = 36V
50
40
30
20
0.01
FRONT PAGE APPLICATION
VOUT = 3.3V
R1 = 1M
R2 = 576k
0.1 1 10
LOAD CURRENT (mA)
100
3970 G01
Efficiency, VOUT = 5V
90
FRONT PAGE APPLICATION
80
VIN = 24V
70
VIN = 12V
60 VIN = 36V
50
40
30
0.01
0.1 1 10
LOAD CURRENT (mA)
100
3970 G02
LT3970 Feedback Voltage
1.220
1.215
1.210
1.205
1.200
1.195
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3970 G03
LT3970-3.3 Output Voltage
3.32
3.31
3.30
LT3970-5 Output Voltage
5.04
5.02
5.00
3.29
3.28
3.27
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3970 G03a
4.98
4.96
4.94
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3970 G03b
No-Load Supply Current
4.0
FRONT PAGE APPLICATION
VOUT = 3.3V
3.5
R1 = 1MΩ
R2 = 576k
LT3970-5
LT3970-3.3
3.0
2.5
2.0
1.5
5
10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3970 G04
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