Switching Regulator. LT3508 Datasheet

LT3508 Regulator. Datasheet pdf. Equivalent

Part LT3508
Description Dual Monolithic 1.4A Step-Down Switching Regulator
Feature www.DataSheet4U.com FEATURES n n n n n n n n n n LT3508 Dual Monolithic 1.4A Step-Down Switching R.
Manufacture Linear Technology
Total Page 26 Pages
Datasheet
Download LT3508 Datasheet



LT3508
FEATURES
n Wide Input Voltage Range: 3.7V to 36V
n Two 1.4A Output Switching Regulators with Internal
Power Switches
n Adjustable 250kHz to 2.5MHz Switching Frequency
n Synchronizable over the Full Frequency Range
n Anti-Phase Switching Reduces Ripple
n Uses Small Inductors and Ceramic Capacitors
n Accurate Programmable Undervoltage Lockout
n Independent Tracking, Soft-Start and Power Good
Circuits Ease Supply Sequencing
n Output Adjustable Down to 800mV
n Small 4mm × 4mm 24-Pin QFN or 16-Pin Thermally
Enhanced TSSOP Surface Mount Packages
APPLICATIONS
n Automotive
n DSP Power Supplies
n Wall Transformer Regulation
n DSL and Cable Modems
n PCI Express
LT3508
Dual Monolithic 1.4A
Step-Down Switching
Regulator
DESCRIPTION
The LT®3508 is a dual current mode PWM step-down
DC/DC converter with internal power switches capable of
generating two 1.4A outputs. The wide input voltage range
of 3.7V to 36V makes the LT3508 suitable for regulating
power from a wide variety of sources, including automo-
tive batteries, 24V industrial supplies and unregulated wall
adapters. Both converters are synchronized to a single os-
cillator programmable up to 2.5MHz and run with opposite
phases, reducing input ripple current. Its high operating
frequency allows the use of small, low cost inductors and
ceramic capacitors, resulting in low, predictable output
ripple. Each regulator has independent tracking and soft-
start circuits and generates a power good signal when its
output is in regulation, easing power supply sequencing
and interfacing with microcontrollers and DSPs.
Cycle-by-cycle current limit, frequency foldback and ther-
mal shutdown provide protection against shorted outputs,
and soft-start eliminates input current surge during start-
up. The low current (<2μA) shutdown mode enables easy
power management in battery-powered systems.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
3.3V and 5V Dual Output Step-Down Converter with Output Sequencing
VIN
5.6V TO 36V
OUT1
3.3V
1.4A
6.8μH
35.7k
11.5k
22μF
4.7μF
VIN1 VIN2 SHDN
BOOST1 BOOST2
0.22μF
SW1 SW2
LT3508
51k
150pF
FB1
VC1
TRACK/SS1
TRACK/SS2
FB2
VC2
PG1
PG2
GND RT/SYNC
ON OFF
0.22μF 10μH
OUT2
5V
1.4A
56.2k
43k 10.7k
10μF
100k
1nF 52.3k 100pF
fSW = 700kHz
POWER
3508 TA01a GOOD
95
VIN = 12V
90
85
Efficiency
VOUT2 = 5V
VOUT1 = 3.3V
80
75
70
65
0 0.5
1
LOAD CURRENT (A)
1.5
3508 TA01b
3508fd
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LT3508
LT3508
ABSOLUTE MAXIMUM RATINGS (Notes 1, 7)
VIN Pin Voltage............................................(–0.3V), 40V
BOOST Pin Voltage ...................................................60V
BOOST Above SW Voltage ........................................30V
SHDN, PG Voltage.....................................................40V
TRACK/SS, FB, RT/SYNC, VC Voltage..........................6V
Operating Junction Temperature Range (Note 2)
LT3508E............................................. –40°C to 125°C
LT3508I.............................................. –40°C to 125°C
LT3508H ............................................ –40°C to 150°C
Storage Temperature Range
QFN.................................................... –65°C to 150°C
TSSOP ............................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
TSSOP .............................................................. 300°C
PIN CONFIGURATION
TRACK/SS1 1
BOOST1 2
SW1 3
VIN1
VIN2
SW2
4
5
6
BOOST2 7
TRACK/SS2 8
TOP VIEW
16 FB1
15 VC1
14 PG1
17 13 RT/SYNC
GND 12 SHDN
11 PG2
10 VC2
9 FB2
FE PACKAGE
16-LEAD PLASTIC TSSOP
θJA = 40°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 17) IS GND AND MUST BE SOLDERED TO PCB
TOP VIEW
24 23 22 21 20 19
FB1 1
TRACK/SS1 2
GND 3
GND 4
GND 5
GND 6
18 FB2
17 TRACK/SS2
25 16 GND
GND 15 GND
14 GND
13 GND
7 8 9 10 11 12
UF PACKAGE
24-LEAD (4mm × 4mm) PLASTIC QFN
θJA = 40°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 25) IS GND AND MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3508EFE#PBF
LT3508EFE#TRPBF
3508FE
16-Lead Plastic TSSOP
–40°C to 125°C
LT3508IFE#PBF
LT3508IFE#TRPBF
3508FE
16-Lead Plastic TSSOP
–40°C to 125°C
LT3508HFE#PBF
LT3508HFE#TRPBF
3508HFE
16-Lead Plastic TSSOP
–40°C to 150°C
LT3508EUF#PBF
LT3508EUF#TRPBF
3508
24-Lead (4mm × 4mm) Plastic QFN –40°C to 125°C
LT3508IUF#PBF
LT3508IUF#TRPBF
3508
24-Lead (4mm × 4mm) Plastic QFN –40°C to 125°C
LT3508HUF#PBF
LT3508HUF#TRPBF
3508H
24-Lead (4mm × 4mm) Plastic QFN –40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.*Temperature grades are 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/
3508fd
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