Datasheet

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LT3483/LT3483A

3483fc

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Inverting Micropower

DC/DC Converters

with Schottky

The LT

3483/LT3483A are micropower inverting DC/DC

converters 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 40mm

. The devices feature a quiescent

current of only 40µA at no load, which further reduces

to 0.1µA 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 10µA feedback current enables one

resistor feedback and virtually eliminates feedback load-

ing of the output. The 40V switch enables voltage outputs

up to –38V to be generated without the use of costly

transformers. The LT3483/LT3483A’s low 300ns off-time

permits the use of tiny low proﬁle inductors and capaci-

tors to minimize footprint and cost in space-conscious

portable applications.

3.6V to –8V DC/DC Converter

Internal 40V Schottky Diode

One Resistor Feedback (Other Resistor Inside)

Internal 40V, 200mA/400mA Power Switch

Generates Regulated Negative Outputs to –38V

Low Quiescent Current:

40µA in Active Mode

<1µA in Shutdown Mode

Low V

CESAT

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 (LT3483 Only) and

Low Proﬁle 8-Lead DFN (2mm × 2mm × 0.75mm)

Packages

LCD Bias

Handheld Computers

Battery Backup

Digital Cameras

OLED Bias

Efﬁciency and Power Loss

10µH

LT3483

4.7µF

0.22µF

10Ω

806k5pF

2.2µF

3483 TA01a

OUT

–8V

25mA

3.6V

SHDN

GND

LOAD CURRENT (mA)

0.1

EFFICIENCY (%)

POWER LOSS (mW)

0.1

100

= 3.6V

POWER

LOSS

1000

1 10

3483 TA01b

100

EFFICIENCY

L, LT, LTC, LTM, Linear Technology 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. Protected by U.S. Patents, including 7710700.

Summary of content (12 pages)

PAGE 1
LT3483/LT3483A Inverting Micropower DC/DC Converters with Schottky DESCRIPTION FEATURES Internal 40V Schottky Diode n One Resistor Feedback (Other Resistor Inside) n Internal 40V, 200mA/400mA Power Switch n Generates Regulated Negative Outputs to –38V n Low Quiescent Current: 40µA in Active Mode <1µA in Shutdown Mode n Low V CESAT Switch: 200mV at 150mA n Wide Input Range: 2.
PAGE 2
LT3483/LT3483A 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/LT3483AE.......
PAGE 3
LT3483/LT3483A ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, VSHDN = 3.6V unless otherwise specified. PARAMETER CONDITIONS MIN VIN Operating Range TYP 2.5 VIN Undervoltage Lockout MAX UNITS 16 V 2 2.4 V FB Comparator Trip Voltage to GND (VFB) FB Falling ● 0 5 12 mV FB Output Current (Note 3) FB = VFB – 5mV ● –10.2 –10 –9.
PAGE 4
LT3483/LT3483A TYPICAL PERFORMANCE CHARACTERISTICS VFB Current 16 10.2 VFB Voltage Switch Off Time 400 350 VFB VOLTAGE (mV) VFB CURRENT (µA) 10.0 SWITCH OFF TIME (ns) 12 10.1 8 4 9.9 300 250 200 150 100 50 9.
PAGE 5
LT3483/LT3483A PIN FUNCTIONS (DFN/TSOT-23) FB (Pin 1/Pin 3): Feedback. Place resistor to negative output here. Set resistor value R1 = VOUT/10µA. 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). 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.
PAGE 6
LT3483/LT3483A OPERATION The LT3483/LT3483A use 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.
PAGE 7
LT3483/LT3483A APPLICATIONS INFORMATION value recommended, as too large of an inductance will increase the output voltage ripple without providing much additional output current. to 4.7µF. The following formula is useful to estimate the output capacitor value needed: COUT = Table 1. Recommended Inductors PART MAX L IDC DCR HEIGHT (µH) (mA) (Ω) (mm) MANUFACTURER LQH2MCN4R7M02L LQH2MCN6R8M02L LQH2MCN100M02L 4.7 6.8 10 300 255 225 0.84 1.0 1.2 0.95 Murata www.murata.com SDQ12 Coupled Inductor 4.
PAGE 8
LT3483/LT3483A 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.
PAGE 9
LT3483/LT3483A TYPICAL APPLICATIONS 3.6V to –8V DC/DC Converter Low Profile, Small Footprint VIN 3.6V C2 0.22µF L1 10µH VIN C1 4.7µF SW Switching Waveform D1 VOUT 20mV/DIV 10Ω VOUT –8V 25mA D LT3483 5pF SHDN FB GND C3 2.
PAGE 10
LT3483/LT3483A PACKAGE DESCRIPTION S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636 Rev B) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 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 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 11
LT3483/LT3483A REVISION HISTORY (Revision history begins at Rev C) REV DATE DESCRIPTION C 09/10 Revised entire data sheet to add LTC3483A PAGE NUMBER 1-12 3483fc 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.
PAGE 12
LT3483/LT3483A TYPICAL APPLICATION –5V Step-Up/Step-Down Converter L1A 4.7µH VIN 2.5V TO 6V L1B 4.7µH • • SW VIN C1 4.7µF VOUT –5V D LT3483A 22pF FB SHDN GND C1: TAIYO YUDEN EMK316BJ475ML C2: TAIYO YUDEN JMK316BJ106ML L1A, L1B: COILTRONICS SDQ12-4R7 OR COILCRAFT LPD3015-472 Efficiency and Power Loss vs Load Current 210 VIN = 3.6V 60 180 50 150 40 120 30 90 20 60 10 30 0 0.