View LT3483EDC-PBF_4320366.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

FEATURES
n n n n n
LT3483 Inverting Micropower DC/DC Converter with Schottky DESCRIPTION
The LT(R)3483 is a micropower inverting DC/DC converter with integrated Schottky and one resistor feedback. The small package size, high level of integration and use of tiny surface mount components yield a solution size as small as 40mm2. The device features a quiescent current of only 40A at no load, which further reduces to 0.1A in shutdown. A current limited, fixed off-time control scheme conserves operating current, resulting in high efficiency over a broad range of load current. A precisely trimmed 10A feedback current enables one resistor feedback and virtually eliminates feedback loading of the output. The 40V switch enables voltage outputs up to -38V to be generated without the use of costly transformers. The LT3483's low 300ns off-time permits the use of tiny low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications. The LT3483 is available in the low profile (1mm) SOT-23 (ThinSOTTM) and 8-lead DFN (2mm x 2mm x 0.75mm) packages.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patent Pending
n n n n n
Internal 40V Schottky Diode One Resistor Feedback (Other Resistor Inside) Internal 40V, 200mA Power Switch Generates Regulated Negative Outputs to -38V Low Quiescent Current: 40A in Active Mode <1A in Shutdown Mode Low VCESAT Switch: 200mV at 150mA Wide Input Range: 2.5V to 16V Uses Small Surface Mount Components Output Short-Circuit Protected Available in a 6-Lead SOT-23 and Low Profile 8-Lead DFN (2mm x 2mm x 0.75mm) Packages
APPLICATIONS
n n n n n
LCD Bias Handheld Computers Battery Backup Digital Cameras OLED Bias
TYPICAL APPLICATION
3.6V to -8V DC/DC Converter
VIN 3.6V 10H 0.22F 75
Efficiency and Power Loss
VIN = 3.6V EFFICIENCY 1000
10 VIN 4.7F LT3483 SHDN FB GND D 5pF 806k EFFICIENCY (%) SW VOUT -8V 25mA 2.2F
70
100 POWER LOSS (mW)
65 POWER LOSS 60
10
1
3483 TA01a
55 0.1 1 10 LOAD CURRENT (mA)
0.1 100
3483 TA01b
3483fb
1
LT3483 ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN Voltage ............................................................... 16V SW Voltage .............................................................. 40V D Voltage ............................................................... -40V FB Voltage ............................................................... 2.5V SHDN Voltage .......................................................... 16V
Operating Ambient Temperature Range (Note 2) LT3483E ...............................................- 40C to 85C LT3483I ..............................................- 40C to 125C Junction Temperature ......................................... 125C Storage Temperature Range.................. -65C to 150C Lead Temperature (Soldering, 10 sec) (TSOT-23 Package Only) .................................. 300C
PIN CONFIGURATION
TOP VIEW TOP VIEW FB 1 GND 2 GND 3 SW 4 9 8 SHDN 7D 6 NC 5 VIN S6 PACKAGE 6-LEAD PLASTIC TSOT-23 TJMAX = 125C, JA = 256C/W IN FREE AIR JA = 120C/W ON BOARD OVER GROUND PLANE SW 1 GND 2 FB 3 6 VIN 5D 4 SHDN
DC PACKAGE 8-LEAD (2mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 121C/W EXPOSED PAD (PIN 9) IS GND
ORDER INFORMATION
LEAD FREE FINISH LT3483EDC#PBF LT3483ES6#PBF LT3483IDC#PBF LT3483IS6#PBF LEAD BASED FINISH LT3483EDC LT3483ES6 TAPE AND REEL LT3483EDC#TRPBF LT3483ES6#TRPBF LT3483IDC#TRPBF LT3483IS6#TRPBF TAPE AND REEL LT3483EDC#TR LT3483ES6#TR PART MARKING LCYT LTBKX LCYT LTBKX PART MARKING LCYT LTBKX PACKAGE DESCRIPTION 8-Lead (2mm x 2mm) Plastic DFN 6-Lead Plastic TSOT-23 8-Lead (2mm x 2mm) Plastic DFN 6-Lead Plastic TSOT-23 PACKAGE DESCRIPTION 8-Lead (2mm x 2mm) Plastic DFN 6-Lead Plastic TSOT-23 TEMPERATURE RANGE -40C to 85C -40C to 85C -40C to 125C -40C to 125C TEMPERATURE RANGE -40C to 85C -40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/
3483fb
2
LT3483 ELECTRICAL CHARACTERISTICS
PARAMETER VIN Operating Range VIN Undervoltage Lockout FB Comparator Trip Voltage to GND (VFB) FB Output Current (Note 3) FB Comparator Hysteresis Quiescent Current in Shutdown Quiescent Current (Not Switching) IFB Line Regulation Switch Off-Time Switch Current Limit Switch VCESAT Switch Leakage Current Rectifier Leakage Current Rectifier Forward Drop SHDN Input Low Voltage SHDN Input High Voltage SHDN Pin Current 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. 1.5 6 10 ISW = 150mA to GND SW = 40V D = - 40V ID = 150mA to GND 0.64 0.4 170 FB Falling FB = VFB - 5mV FB Rising VSHDN = GND FB = -0.05V 2.5V VIN 16V 300 200 200 1 4 230 40

The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 3.6V, VSHDN = 3.6V unless otherwise specified.
CONDITIONS MIN 2.5 2 0 -10.2 5 -10 10 1 50 0.07 TYP MAX 16 2.4 12 -9.7 UNITS V V mV A mV A A %/V ns mA mV A A V V V A
Note 2: The LT3483E is guaranteed to meet specifications from 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT3483I is guaranteed to meet specifications over the -40C to 125C operating temperature range. Note 3: Current flows out of the pin.
3483fb
3
LT3483 TYPICAL PERFORMANCE CHARACTERISTICS
VFB Current
10.2 16
VFB Voltage
400 350 SWITCH OFF TIME (ns) -25 50 75 0 25 TEMPERATURE (C) 100 125
Switch Off Time
10.1 VFB CURRENT (A) VFB VOLTAGE (mV)
12
300 250 200 150 100 50
10.0
8
9.9
4
9.8 -50
-25
50 75 0 25 TEMPERATURE (C)
100
125
0 -50
0 -50
-25
0
25 75 50 TEMPERATURE (C)
100
125
3483 G01
3483 G02
3483 G03
Switch Current Limit
230 220 210 200 190 180 170 -50 QUIESCENT CURRENT (A) 50
Quiescent Current
10 SHDN PIN BIAS CURRENT (A)
SHDN Pin Bias Current
TA = 25C
SWITCH CURRENT LIMIT (mA)
40
8
30
6
20
4
10
2
-25
0 25 50 75 TEMPERATURE (C)
100
125
0 -50
-25
50 75 0 25 TEMPERATURE (C)
100
125
0
0
8 4 12 SHDN PIN VOLTAGE (V)
16
3483 G06
3483 G04
3483 G05
3483fb
4
LT3483 PIN FUNCTIONS
(DFN/TSOT-23)
FB (Pin 1/Pin 3): Feedback. Place resistor to negative output here. Set resistor value R1 = VOUT/10A. GND (Pins 2, 3/Pin 2): Ground. For DFN package, tie both pin 2 and pin 3 together to ground. SW (Pin 4/Pin 1): Switch. Connect to external inductor L1 and positive terminal of transfer capacitor. VIN (Pin 5/Pin 6): Input Supply. Must be locally bypassed with 1F or greater. NC (Pin 6/NA): No Connection.
D (Pin 7/Pin 5): Anode Terminal of Integrated Schottky Diode. Connect to negative terminal of transfer capacitor and external inductor L2 (flyback configuration) or to cathode of external Schottky diode (inverting charge pump configuration). SHDN (Pin 8/Pin 4): Shutdown. Connect to GND to turn device off. Connect to supply to turn device on. Exposed Pad (Pin 9/NA): GND. The exposed pad should be soldered to the PCB ground to achieve the rated thermal performance.
BLOCK DIAGRAM
L1A VIN L1B
*
CFLY
*
VOUT COUT
6 VIN 1.250V REFERENCE 125k R1 VOUT 3 FB 300ns DELAY S R Q Q
1 SW
5 D
Q1
D1 25mV
+
A3
+
A2
-
A1
+
0.1 0.1
-
20mV
-
GND 2 OPTIONAL CHARGE PUMP CONFIGURATION. L1B REPLACED WITH: D2 D R2 VOUT PIN NUMBERS CORRESPOND TO THE 6-PIN TSOT-23 PACKAGE
3483 BD
3483fb
5
LT3483 OPERATION
The LT3483 uses a constant off-time control scheme to provide high efficiency over a wide range of output currents. Operation can be best understood by referring to the Block Diagram. When the voltage at the FB pin is approximately 0V, comparator A3 disables most of the internal circuitry. Output current is then provided by external capacitor COUT, which slowly discharges until the voltage at the FB pin goes above the hysteresis point of A3. Typical hysteresis at the FB pin is 10mV. A3 then enables the internal circuitry, turns on power switch Q1, and the currents in external inductors L1A and L1B begin to ramp up. Once the switch current reaches 200mA, comparator A1 resets the latch, which turns off Q1 after about 80ns. Inductor current flows through the internal Schottky D1 to GND, charging the flying capacitor. Once the 300ns off-time has elapsed, and internal diode current drops below 250mA (as detected by comparator A2), Q1 turns on again and ramps up to 200mA. This switching action continues until the output capacitor charge is replenished (until the FB pin decreases to 0V), then A3 turns off the internal circuitry and the cycle repeats. The inverting charge pump topology replaces L1B with the series combination D2 and R2.
APPLICATIONS INFORMATION
CHOOSING A REGULATOR TOPOLOGY Inverting Charge Pump The inverting charge pump regulator combines an inductor-based step-up with an inverting charge pump. This configuration usually provides the best size, efficiency and output ripple and is applicable where the magnitude of VOUT is greater than VIN. Negative outputs to -38V can be produced with the LT3483 in this configuration. For cases where the magnitude of VOUT is less than or equal to VIN, use a 2-inductor or transformer configuration such as the inverting flyback. In the inverting charge pump configuration, a resistor is added in series with the Schottky diode between the negative output and the D pin of the LT3483. The purpose of this resistor is to smooth/reduce the current spike in the flying capacitor when the switch turns on. A 10 resistor works well for a Li+ to -8V application, and the impact to converter efficiency is less than 3%. The resistor values recommended in the applications circuits also limit the switch current during a short-circuit condition at the output. Inverting Flyback The inverting flyback regulator, shown in the -5V application circuit, uses a coupled inductor and is an excellent choice where the magnitude of the output is less than or equal to the supply voltage. The inverting flyback also performs well in a step-up/invert application, but it occupies more board space compared with the inverting charge pump. Also, the maximum |VOUT| using the flyback is less than can be obtained with the charge pump--it is reduced from 38V by the magnitudes of VIN and ringing at the switch node. Under a short-circuit condition at the output, a proprietary technique limits the switch current and prevents damage to the LT3483 even with supply voltage as high as 16V. As an option, a 0.47F capacitor may be added between terminals D and SW of LT3483 to suppress ringing at SW. Inductor Selection Several recommended inductors that work well with the LT3483 are listed in Table 1, although there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts. Many different sizes and shapes are available. For inverting charge pump regulators with input and output voltages below 7V, a 4.7H or 6.8H inductor is usually the best choice. For flyback regulators or for inverting charge pump regulators where the input or output voltage is greater than 7V, a 10H inductor is usually the best choice. A larger value inductor can be used to slightly increase the available output current, but limit
3483fb
6
LT3483 APPLICATIONS INFORMATION
it to around twice the value recommended, as too large of an inductance will increase the output voltage ripple without providing much additional output current.
Table 1. Recommended Inductors
MAX L IDC DCR HEIGHT (H) (mA) () (mm) MANUFACTURER 4.7 6.8 10 10 15 10 300 255 225 980 780 550 0.84 1.0 1.2 0.72 1.15 0.46 0.95 Murata www.murata.com Cooper Electronics Tech www.cooperet.com Wurth Elektronik www.we-online.com
to 4.7F The following formula is useful to estimate the . output capacitor value needed: COUT = L *ISW 2 -VOUT * VOUT
PART LQH2MCN4R7M02L LQH2MCN6R8M02L LQH2MCN100M02L SDQ12 Coupled Inductor 744876 Coupled Inductor
1.2
where ISW = 0.25A and VOUT = 30mV. The flying capacitor in the inverting charge pump configuration ranges from 0.1F to 0.47F Multiply the value predicted by the above . equation for COUT by 1/10 to determine the value needed for the flying capacitor.
Table 2. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER AVX Kemet Murata Taiyo Yuden URL www.avxcorp.com www.kemet.com www.murata.com www.tyuden.com
1.2
Capacitor Selection The small size and low ESR of ceramic capacitors make them ideal for LT3483 applications. Use of X5R and X7R types is recommended because they retain their capacitance over wider voltage and temperature ranges than other dielectric types. Always verify the proper voltage rating. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for more detailed information on their entire selection of ceramic capacitors. A 4.7F ceramic bypass capacitor on the VIN pin is recommended where the distance to the power supply or battery could be more than a couple inches. Otherwise, a 1F is adequate. A capacitor in parallel with feedback resistor R1 is recommended to reduce the output voltage ripple. Use a 5pF capacitor for the inverting charge pump, and a 22pF value for the inverting flyback or other dual inductor configurations. Output voltage ripple can be reduced to 20mV in some cases using this capacitor in combination with an appropriately selected output capacitor. The output capacitor is selected based on desired output voltage ripple. For low output voltage ripple in the inverting flyback configuration, use a 4.7F to 10F capacitor. The inverting charge pump utilizes values ranging from 0.22F
Setting the Output Voltage The output voltage is programmed using one feedback resistor according to the following formula: R1= - VOUT 10A
Inrush Current When VIN is increased from ground to operating voltage, an inrush current will flow through the input inductor and integrated Schottky diode to charge the flying capacitor. Conditions that increase inrush current include a larger, more abrupt voltage step at VIN, a larger flying capacitor, and an inductor with a low saturation current. While the internal diode is designed to handle such events, the inrush current should not be allowed to exceed 1.5A. For circuits that use flying capacitors within the recommended range and have input voltages less than 5V, inrush current remains low, posing no hazard to the device. In cases where there are large steps at VIN, inrush current should be measured to ensure operation within the limits of the device.
3483fb
7
LT3483 APPLICATIONS INFORMATION
Board Layout Considerations As with all switching regulators, careful attention must be given to the PCB board layout and component placement. Proper layout of the high frequency switching path is essential. The voltage signals of the SW and D pins have sharp rising and falling edges. Minimize the length and area of all traces connected to the SW and D pins. In particular, it is desirable to minimize the trace length to and from the flying capacitor, since current in this capacitor switches directions within a cycle. Always use a ground plane under the switching regulator to minimize interplane coupling.
Suggested Layout (DFN) for Inverting Charge Pump
VOUT COUT
R1 A SHDN 1 2 3 9 8 7 6 5 VIN CFLY K
GND
4
CIN L1
3483 AI02
Suggested Layout (SOT-23) for Inverting Charge Pump +
GND CIN L1 CFLY VIN 1 2 3 COUT R1 SHDN 6 5 4
VOUT
3483 AI01
3483fb
8
LT3483 TYPICAL APPLICATION
3.6V to -8V DC/DC Converter Low Profile, Small Footprint
L1 10H C2 0.22F D1 10 SW VIN C1 4.7F LT3483 SHDN FB GND D 5pF R1 806k
VIN 3.6V
VOUT -8V 25mA C3 2.2F
C1: MURATA GRM219R61A475KE34B C2: TAIYO YUDEN LMK107BJ224 C3: MURATA GRM219R61C225KA88B D1: PHILIPS PMEG2005EB L1: MURATA LQH2MCN100K02L
3483 TA04a
Switching Waveform
VOUT 20mV/DIV
ISW 100mA/DIV
2s/DIV
3483 TA04b
3483fb
9
LT3483 PACKAGE DESCRIPTION
DC Package 8-Lead Plastic DFN (2mm x 2mm)
(Reference LTC DWG # 05-08-1719 Rev O)
0.70 0.05 2.55 0.05 1.15 0.05 0.64 0.05 (2 SIDES) PACKAGE OUTLINE
0.25 0.05 0.45 BSC 1.37 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED R = 0.05 TYP 2.00 0.10 (4 SIDES)
R = 0.115 TYP 5
8 0.40 0.10 PIN 1 NOTCH R = 0.20 OR 0.25 x 45 CHAMFER
(DC8) DFN 0106 REVO
PIN 1 BAR TOP MARK (SEE NOTE 6)
0.64 0.10 (2 SIDES)
4 0.200 REF 0.75 0.05 1.37 0.10 (2 SIDES) 0.00 - 0.05
1 0.23 0.05 0.45 BSC
BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
3483fb
10
LT3483 PACKAGE DESCRIPTION
S6 Package 6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636 Rev B)
0.62 MAX 0.95 REF 2.90 BSC (NOTE 4)
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 - 1.75 (NOTE 4) PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR
0.95 BSC
0.30 - 0.45 6 PLCS (NOTE 3)
0.80 - 0.90 0.20 BSC DATUM `A' 1.00 MAX 0.01 - 0.10
0.30 - 0.50 REF
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
0.09 - 0.20 (NOTE 3)
1.90 BSC
S6 TSOT-23 0302 REV B
3483fb
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.
11
LT3483 TYPICAL APPLICATIONS
3.6V to -22V DC/DC Converter
L1 10H C2 0.1F D1 EFFICIENCY EFFICIENCY (%) SW VIN C1 4.7F LT3483 SHDN FB GND D 5pF R1 2.2M C3 1F RS 30 70 VOUT -22V 8mA 100 POWER LOSS (mW)
3.6V to -22V Converter Efficiency and Power Loss
75 1000
VIN 3.6V
65 POWER LOSS 60
10
1
C1: TAIYO YUDEN LMK316BJ475MD C2: TAIYO YUDEN TMK107BJ104 (X5R) C3: TAIYO YUDEN TMK316BJ105MD D1: PHILIPS PMEG3002AEB L1: MURATA LQH2MCN100K02L
3483 TA02a
55 0.1
1 LOAD CURRENT (mA)
0.1 10
3483 TA02b
-5V DC/DC Converter
L1A 10H VIN 1nF 10 L1B 10H 75
- 5V Efficiency
*
SW VIN D
*
70 EFFICIENCY (%) VOUT -5V 22pF 511k C2 10F VIN = 5V 65 VIN = 12V 60
C1 4.7F
LT3483 SHDN FB GND
C1: TAIYO YUDEN EMK316BJ475ML C2: TAIYO YUDEN JMK316BJ106ML L1A, L1B: WURTH 744876100
3483 TA03a
55 0.1 1 10 LOAD CURRENT (mA) 100
3483 TA03b
RELATED PARTS
PART NUMBER LT1617/LT1617-1 LT1931/LT1931A LT1945 LT3463 DESCRIPTION 350mA/100mA (ISW) High Efficiency Micropower Inverting DC/DC Converter 1A (ISW), 1.2MHz/2.2MHz, High Efficiency Micropower Inverting DC/DC Converter Dual Output, Boost/Inverter, 350mA (ISW), Constant Off-Time, High Efficiency Step-Up DC/DC Converter Dual Output, Boost/Inverter, 250mA (ISW), Constant Off-Time, High Efficiency Step-Up DC/DC Converter with Integrated Schottky Diodes 85mA (ISW), High Efficiency Step-Up DC/DC Converter with Integrated Schottky and PNP Disconnect Boost (350mA) and Inverting (400mA) DC/DC Converter for CCD Bias with Integrated Schottkys COMMENTS VIN: 1.2V to 15V, VOUT(MAX) = -34V, IQ = 20A, ISD < 1A ThinSOT Package VIN: 2.6V to 16V, VOUT(MAX) = -34V, IQ = 5.8mA, ISD < 1A ThinSOT Package VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 40A, ISD < 1A, MS10 Package VIN: 2.3V to 15V, VOUT(MAX) = 40V, IQ = 40A, ISD < 1A DFN Package VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25A, ISD < 1A ThinSOT Package VIN: 2.3V to 15V, VOUT(MAX) = 40V, IQ = 2.8mA, ISD < 1A DFN Package
3483fb
LT3464 LT3472
12 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0508 REV B * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2004

▲Up To Search▲

Price & Availability of LT3483EDC-PBF

	To Download LT3483EDC-PBF Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .