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Final Electrical Specifications
LT3460 1.3MHz Step-Up DC/DC Converter in SC70 and ThinSOT
FEATURES
s s s s s s s s s
DESCRIPTIO
March 2003
1.3MHz Switching Frequency High Output Voltage: Up to 36V 300mA Integrated Switch 12V at 70mA from 5V Input 5V at 60mA from 3.3V Input Wide Input Range: 2.5V to 16V Uses Small Surface Mount Components Low Shutdown Current: <1A SC70 and Low Profile (1mm) ThinSOTTM Packages
The LT(R)3460 is a general purpose step-up DC/DC converter. The LT3460 switches at 1.3MHz, allowing the use of tiny, low cost and low height capacitors and inductors. The constant frequency results in low, predictable output noise that is easy to filter. The high voltage switch in the LT3460 is rated at 38V, making the device ideal for boost converters up to 36V. The LT3460 can generate 12V at up to 70mA from a 5V supply. The LT3460 is available in SC70 and ThinSOT packages.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation
APPLICATIO S
s s s s s s s
Digital Cameras CCD Bias Supply XDSL Power Supply TFT-LCD Bias Supply Local 5V or 12V Supply Medical Diagnostic Equipment Battery Backup
TYPICAL APPLICATIO
90 85
EFFICIENCY (%)
VIN 5V C1 4.7F OFF ON 4
L1 22H 5 VIN LT3460 SHDN GND 2 FB 1 SW
D1
VOUT 12V 70mA 130k 22pF
80 75 70 65 60
3 15k
C2 1F
0
C1: TAIYO YUDEN X5R JMK212BJ475KG C2: TAIYO YUDEN X5R EMK316BJ105 D1: CENTRAL SEMICONDUCTOR CMDSH2-3 L1: MURATA LQH32CN-220 OR EQUIVALENT
3460 F01
Figure 1. 5V to 12V, 70mA Step-Up DC/DC Converter
VSW 5V/DIV IL 100mA/DIV
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
Efficiency
20 40 60 LOAD CURRENT (mA)
0.2s/DIV
U
U
80
3460 F01a
Switching Waveforms
3460 F01b
3460i
1
LT3460
ABSOLUTE AXI U RATI GS
Input Voltage (VIN) .................................................. 16V SW Voltage .............................................................. 38V FB Voltage ................................................................. 5V SHDN Voltage .......................................................... 16V
PACKAGE/ORDER I FOR ATIO
TOP VIEW SW 1 GND 2 FB 3 4 SHDN 5 VIN
ORDER PART NUMBER
TOP VIEW
LT3460ES5
S5 PACKAGE 5-LEAD PLASTIC TSOT-23
TJMAX = 125C, JA = 256C/W IN FREE AIR JA = 120C ON BOARD OVER GROUND PLANE
S5 PART MARKING LTB1
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VIN = 3V, VSHDN = 3V, unless otherwise noted.
PARAMETER Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
Feedback Line Regulation FB Pin Bias Current Supply Current SHDN = 0V Switching Frequency Maximum Duty Cycle Switch Current Limit Switch VCESAT Switch Leakage Current SHDN Voltage High SHDN Voltage Low SHDN Pin Bias Current Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. ISW = 250mA VSW = 5V 1.5 1.0 85 300
q
2
U
U
W
WW
U
W
(Note 1)
Operating Ambient Temperature Range (Note 2) .................. - 40C to 85C Maximum Junction Temperature .......................... 125C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER
SW 1 GND 2 FB 3 6 VIN 5 GND 4 SHDN
LT3460ESC6
SC6 PACKAGE 6-LEAD PLASTIC SC70
TJMAX = 125C, JA = 400C/W IN FREE AIR JA = 270C/W ON BOARD OVER GROUND PLANE
SC6 PART MARKING LAAF
MIN 2.5
TYP
MAX 16
UNITS V V V V %/V nA mA A MHz % mA mV A V V A
1.235 1.225 5
1.255 0.0015 25 2.0 0.1 1.3 90 420 320 0.01
1.275 1.280 80 3.0 0.5 1.7 600 450 1 0.4
40
Note 2: The LT3460E is guaranteed to meet specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
3460i
LT3460
PI FU CTIO S
SW (Pin 1/Pin 1): Switch Pin. Connect inductor/diode here. Minimize trace at this pin to reduce EMI. GND (Pin 2/Pins 2 and 5): Ground Pin. Tie directly to local ground plane. FB (Pin 3/Pin 3): Feedback Pin. Reference voltage is 1.255V. Connect resistor divider tap here. Minimize trace area at FB. Set VOUT according to VOUT = 1.255V (1 + R1/R2).
BLOCK DIAGRA
VIN (PIN 6 SC70 PACKAGE) 5 VOUT R1 (EXTERNAL) FB R2 (EXTERNAL)
1.255V REFERENCE
SHUTDOWN
RS (EXTERNAL)
4 SHDN CS (EXTERNAL)
RS, CS OPTIONAL SOFT-START COMPONENTS
OPERATIO
The LT3460 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the block diagram in Figure 2. At the start of each oscillator cycle, the SR latch is set, which turns on the power switch Q1. A voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the PWM comparator A2. When this voltage exceeds the level at the negative input of A2, the SR
W
U
U
U
U
(ThinSOT/SC70 Packages)
SHDN (Pin 4/Pin 4): Shutdown Pin. Tie to 1.5V or higher to enable device; 0.4V or less to disable device. Also functions as soft-start. Use RC filter (47k, 47nF typ) as shown in Figure 2. VIN (Pin 5/Pin 6): Input Supply Pin. Must be locally bypassed.
+
A1
COMPARATOR
1 DRIVER
SW
-
RC CC A2 R S Q
-
3 FB
Q1
+
+
0.1
-
RAMP GENERATOR
1.3MHz OSCILLATOR
2
GND (PINS 2 AND 5 SC70 PACKAGE)
3460 BD
Figure 2. Block Diagram
latch is reset turning off the power switch. The level at the negative input of A2 is set by the error amplifier A1, and is simply an amplified version of the difference between the feedback voltage and the reference voltage of 1.255V. In this manner, the error amplifier sets the correct peak current level to keep the output in regulation. If the error amplifier's output increases, more current is delivered to the output; if it decreases, less current is delivered.
3460i
3
LT3460
OPERATIO
Layout Hints The high speed operation of the LT3460 demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 3 shows the recommended component placement.
VOUT
+
C2 R2 SHUTDOWN
GND
TYPICAL APPLICATIO S
5V to 12V Step-Up Converter
VIN 5V C1 4.7F SHDN 4 L1 22H 5 VIN LT3460 SHDN GND 2 C1: TAIYO YUDEN X5R JMK212BJ475 C2: TAIYO YUDEN X5R EMK212BJ105 D1: CENTRAL SEMICONDUCTOR CMDSH2-3 L1: MURATA LQH32CN-220 OR EQUIVALENT FB 3 15k C2 1F 1 SW 130k 22pF
90
D1
EFFICIENCY (%)
VOUT 100mV/DIV
58mA ILOAD 34mA 100s/DIV
4
U
U
D1 L1 C1 D1 VIN VOUT L1 C1
+ +
C2 R2
+
VIN SHUTDOWN
R1
C3
GND
R1
C3
(SOT-23 PACKAGE)
(SC70 PACKAGE)
3460 F02
Figure 3. Suggested Layout
Efficiency
VOUT 12V 70mA
85 80 75 70 65
3460 TA01
60
0
20 40 60 LOAD CURRENT (mA)
80
3460 TA01a
Load Step Response
3460 TA01b
3460i
LT3460
TYPICAL APPLICATIO S
5V to 12V with Soft-Start Circuit
VIN 5V C1 4.7F CONTROL SIGNAL VIN 47k SHDN 47nF GND LT3460 FB 15k SW 130k 22pF C2 1F 16V VO 5V/DIV CONTROL SIGNAL 2V/DIV
3460 TA02
L1 22H
D1
C1: TAIYO YUDEN X5R JMK212BJ475 C2: TAIYO YUDEN X5R EMK212BJ105 D1: CENTRAL SEMICONDUCTOR CMDSH2-3 L1: MURATA LQH32CN-220 OR EQUIVALENT
3.3V to 12V Step-Up Converter
VIN 3.3V C1 4.7F L1 22H D1 85 VOUT 12V 40mA 22pF C2 1F 16V 15k EFFICIENCY (%) 130k 80 75 70 65 60 C1: TAIYO YUDEN X5R JMK212BJ475 C2: TAIYO YUDEN X5R EMK212BJ105 D1: CENTRAL SEMICONDUCTOR CMDSH2-3 L1: MURATA LQH32CN-220 OR EQUIVALENT
3460 TA03
VIN LT3460 SHDN GND
SW
FB
U
Input Current and Output Voltage
VOUT 12V 70mA
IIN 100mA/DIV
500s/DIV
3460 TA02b
Efficiency
55 0 20 30 10 LOAD CURRENT (mA) 40
3460 TA03a
3460i
5
LT3460
TYPICAL APPLICATIO S U
12V to 36V Step-Up Converter
VIN 12V C1 1F 16V L1 47H D1 VOUT 36V 4mA 278k 22pF C2 0.22F 50V 10k ILOAD C1: TAIYO YUDEN X5R EMK212BJ105 C2: TAIYO YUDEN X7R UMK212BJ224 D1, D2: CENTRAL SEMICONDUCTOR CMOD4448 L1: TAIYO YUDEN LB2012
3460 TA04
Load Step Response
D2 VIN LT3460 SHDN GND FB SW VOUT 100mV/DIV
4mA 2mA 100s/DIV
3460 TA04a
5V to 36V Step-Up Converter
VIN 5V C1 1F 6.3V L1 47H D1 VOUT 36V 4mA 278k 22pF C2 0.22F 50V 10k ILOAD C1: TAIYO YUDEN X5R JMK107BJ105 C2: TAIYO YUDEN X7R UMK212BJ224 D1, D2: CENTRAL SEMICONDUCTOR CMOD4448 L1: TAIYO YUDEN LB2012
3460 TA05
Load Step Response
D2 VIN LT3460 SHDN GND FB SW VOUT 100mV/DIV
4mA 2mA 100s/DIV
3460 TA05a
3460i
6
LT3460
PACKAGE DESCRIPTIO
0.62 MAX
0.95 REF 0.20 BSC 1.22 REF DATUM `A'
3.85 MAX 2.62 REF
1.4 MIN 0.80 - 0.90 0.01 - 0.10 1.00 MAX
RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193
0.10 - 0.40 0.47 MAX 0.65 REF
1.16 REF 0.10 - 0.30 0.10 - 0.18 (NOTE 3) 3.26 MAX 2.1 REF 0.96 MIN 0.80 - 1.00 0.00 - 0.10 REF 1.00 MAX PIN 1 1.80 - 2.40 1.15 - 1.35 (NOTE 4) INDEX AREA (NOTE 6)
RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. DETAILS OF THE PIN 1 INDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE INDEX AREA 7. EIAJ PACKAGE REFERENCE IS EIAJ SC-70
U
S5 Package 5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
2.90 BSC (NOTE 4) 0.30 - 0.50 REF 0.09 - 0.20 (NOTE 3) 2.80 BSC 1.50 - 1.75 (NOTE 4) PIN ONE 0.30 - 0.45 TYP 5 PLCS (NOTE 3)
S5 TSOT-23 0302
1.90 BSC
0.95 BSC
SC6 Package 6-Lead Plastic SC70
(Reference LTC DWG # 05-08-1638)
1.80 - 2.20 (NOTE 4)
0.65 BSC
0.15 - 0.30 6 PLCS (NOTE 3)
SC6 SC70 0802
3460i
7
LT3460
TYPICAL APPLICATIO S
5V to 5V SEPIC
VIN 3V TO 10V C1 1F L1 22H C3 0.22F D1 VOUT 5V 50mA 30k 50pF C2 1F 10k
C1, C2: TAIYO YUDEN X5R LMK107BJ105 C3: TAIYO YUDEN X7R LMK107BJ224 D1: ON SEMICONDUCTOR MBR0520 L1, L2: MURATA LQH32CN-220 OR EQUIVALENT
EFFICIENCY (%)
RELATED PARTS
PART NUMBER LT1615/LT1615-1 LT1944/LT1944-1 LTC3400/LTC3400B LTC3401 LTC3402 LT3464 DESCRIPTION Constant Off-Time, Step-Up DC/DC Converter Dual Off-Time, Step-Up DC/DC Converter 1.2MHz, Synchronous Step-Up DC/DC Converter 3MHz, Synchronous Step-Up DC/DC Converter 3MHz, Synchronous Step-Up DC/DC Converter Micropower Step-Up DC/DC Converter COMMENTS 350mA Switch, VOUT to 36V, IQ = 20A, ThinSOT Package 350mA Switch x2, VOUT to 36V, IQ = 20A, MS10 Package 600mA Switch, VIN: 0.85V to 5V, IQ = 19A, ThinSOT Package 1A Switch, VIN: 0.5V to 5V, IQ = 38A, MS10 Package 2A Switch, VIN: 0.5V to 5V, IQ = 38A, MS10 Package 85mA Switch, Contains Diode and Output Disconnect PNP, IQ = 25A
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
VIN LT3460 SHDN GND
SW
L2 22H
FB
3460 TA06
Efficiency
80 75 VIN = 4V 70 65 60 55 50 VIN = 5V VIN = 6.5V
0
100 50 LOAD CURRENT (mA)
150
3460 TA06a
3460i LT/TP 0303 1.5K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2003

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