Document
LTC3440
Micropower Synchronous Buck-Boost DC/DC Converter
Features
nn Single Inductor nn Fixed Frequency Operation with Battery Voltages
Above, Below or Equal to the Output nn Synchronous Rectification: Up to 96% Efficiency nn 25µA Quiescent Current in Burst Mode® Operation nn Up to 600mA Continuous Output Current nn No Schottky Diodes Required (VOUT < 4.3V) nn VOUT Disconnected from VIN During Shutdown nn 2.5V to 5.5V Input and Output Range nn Programmable Oscillator Frequency
from 300kHz to 2MHz nn Synchronizable Oscillator nn Burst Mode Enable Control nn <1µA Shutdown Current nn Small Thermally Enhanced 10-Pin MSOP and
(3mm × 3mm) DFN Packages
Applications
nn Palmtop Computers nn Handheld Instruments nn MP3 Players nn Digital Cameras
Description
The LTC®3440 is a high efficiency, fixed frequency, BuckBoost DC/DC converter that operates from input voltages above, below or equal to the output voltage. The topology incorporated in the IC provides a continuous transfer function through all operating modes, making the product ideal for single lithium-ion, multicell alkaline or NiMH applications where the output voltage is within the battery voltage range.
The device includes two 0.19Ω N-channel MOSFET switches and two 0.22Ω P-channel switches. Switching frequencies up to 2MHz are programmed with an external resistor and the oscillator can be synchronized to an external clock. Quiescent current is only 25µA in Burst Mode operation, maximizing battery life in portable applications. Burst Mode operation is user controlled and can be enabled by driving the MODE/SYNC pin high. If the MODE/SYNC pin has either a clock or is driven low, then fixed frequency switching is enabled.
Other features include a 1µA shutdown, soft-start control, thermal shutdown and current limit. The LTC3440 is available in the 10-pin thermally enhanced MSOP and (3mm × 3mm) DFN packages.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Application
Li-Ion to 3.3V at 600mA Buck-Boost Converter
L1 10µH
3 SW1
4 SW2
VIN = 2.7V TO 4.2V
7
LTC3440
6
VIN
VOUT
R1 340k
+
Li-Ion
8 SHDN/SS
9 FB
C5 1.5nF
2
10
C1 *
MODE/SYNC VC
10µF 1 RT
5 GND
RT
R3 15k R2
200k
60.4k
VOUT 3.3V 600mA
C2 22µF
*1 = Burst Mode OPERATION 0 = FIXED FREQUENCY
C1: TAIYO YUDEN JMK212BJ106MG C2: TAIYO YUDEN JMK325BJ226MM L1: SUMIDA CDRH6D38-100
3440 TA01
EFFICIENCY (%)
Efficiency vs VIN
100
98
VOUT = 3.3V IOUT = 100mA
96 fOSC = 1MHz
94
92
90
88
86
84
82
80 2.5 3.0 3.5 4.0 4.5
VIN (V)
5.0 5.5
3440 TA02
For more information www.linear.com/LTC3440
3440fd
1
LTC3440
Absolute Maximum Ratings (Note 1)
VIN, VOUT Voltage ........................................ – 0.3V to 6V SW1, SW2 Voltage....................................... –0.3V to 6V
VC, RT, FB, SHDN/SS, MODE/SYNC Voltage................................... –0.3V to 6V
Operating Temperature Range (Note 2)....–40°C to 85°C Storage Temperature Range................... –65°C to 125°C Lead Temperature (Soldering, 10 sec).................... 300°C
Pin Configuration
TOP VIEW
RT 1 MODE/SYNC 2
10 VC 9 FB
SW1 3
11
8 SHDN/SS
SW2 4 GND 5
7 VIN 6 VOUT
DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 11) IS GND MUST BE SOLDERED TO PCB
TJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W
TOP VIEW
RT 1 MODE/SYNC 2
SW1 3 SW2 4 GND 5
10 VC 9 FB 8 SHDN/SS 7 VIN 6 VOUT
MS PACKAGE 10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 130°C/W 1 layer board θJA = 100°C/W 4 layer board
θJC = 45°C/W
Order Information http://www.linear.com/product/LTC3440#orderinfo
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3440EDD#PBF
LTC3440EDD#TRPBF LBKT
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 85°C
LTC3440EMS#PBF
LTC3440EMS#TRPBF LTNP
10-Lead Plastic MSOP
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on nonstandard 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/. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
Electrical Characteristics The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = VOUT = 3.6V, RT = 60k, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX UNITS
Input Start-Up Voltage
l
2.4
2.5
V
Input Operating Range
l 2.5
5.5
V
Output Voltage Adjust Range
l 2.5
5.5
V
Feedback Voltage
l 1.196 1.22 1.244
V
Feedback Input Current Quiescent Current, Burst Mode Operation Quiescent Current, Shutdown
VFB = 1.22V VC = 0V, MODE/SYNC = .