LT3483EDC#PBF - LINEAR TECHNOLOGY

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 40mm2. 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

n Internal 40V Schottky Diode

One Resistor Feedback (Other Resistor Inside)

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 VCESAT Switch: 200mV at 150mA

n Wide Input Range: 2.5V to 16V

n Uses Small Surface Mount Components

n Output Short-Circuit Protected

n Available in a 6-Lead SOT-23 (LT3483 Only) and

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

Packages

n LCD Bias

Handheld Computers

Battery Backup

Digital Cameras

n OLED Bias

Efﬁciency and Power Loss

10µH

LT3483

4.7µF

0.22µF

VIN

10Ω

806k5pF

2.2µF

3483 TA01a

VOUT

–8V

25mA

VIN

3.6V

SHDN

GND

LOAD CURRENT (mA)

0.1

EFFICIENCY (%)

POWER LOSS (mW)

0.1

100

VIN = 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.

LT3483/LT3483A

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ABSOLUTE MAXIMUM RATINGS

VIN Voltage ............................................................... 16V

SW Voltage .............................................................. 40V

D Voltage ............................................................... –40V

FB Voltage ............................................................... 2.5V

SHDN Voltage .......................................................... 16V

(Note 1)

TOP VIEW

GND

SHDN

VIN

DC PACKAGE

8-LEAD (2mm × 2mm) PLASTIC DFN

TJMAX = 125°C, θJA = 88.5°C/W

EXPOSED PAD (PIN 9) IS GND

SW 1

GND 2

FB 3

6 VIN

5 D

4 SHDN

TOP VIEW

S6 PACKAGE

6-LEAD PLASTIC TSOT-23

TJMAX = 125°C, θJA = 192°C/W

PIN CONFIGURATION

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LT3483EDC#PBF LT3483EDC#TRPBF LCYT 8-Lead (2mm 2mm) Plastic DFN –40°C to 85°C

LT3483ES6#PBF LT3483ES6#TRPBF LTBKX 6-Lead Plastic TSOT-23 –40°C to 85°C

LT3483AEDC#PBF LT3483AEDC#TRPBF LFXD 8-Lead (2mm 2mm) Plastic DFN –40°C to 85°C

LT3483IDC#PBF LT3483IDC#TRPBF LCYT 8-Lead (2mm 2mm) Plastic DFN –40°C to 125°C

LT3483IS6#PBF LT3483IS6#TRPBF LTBKX 6-Lead Plastic TSOT-23 –40°C to 125°C

LT3483AIDC#PBF LT3483AIDC#TRPBF LFXD 8-Lead (2mm 2mm) Plastic DFN –40°C to 125°C

LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LT3483EDC LT3483EDC#TR LCYT 8-Lead (2mm 2mm) Plastic DFN –40°C to 85°C

LT3483ES6 LT3483ES6#TR LTBKX 6-Lead Plastic TSOT-23 –40°C to 85°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is 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/

Operating Ambient Temperature Range (Note 2)

LT3483E/LT3483AE ..............................– 40°C to 85°C

LT3483I/LT3483AI .............................. –40°C to 125°C

Junction Temperature ......................................... 125°C

Storage Temperature Range .................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)

(TSOT-23 Package Only) .................................. 300°C

LT3483/LT3483A

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ELECTRICAL CHARACTERISTICS

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.

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 TYP MAX UNITS

VIN Operating Range 2.5 16 V

VIN Undervoltage Lockout 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 –9.7 µA

FB Comparator Hysteresis FB Rising 10 mV

Quiescent Current in Shutdown VSHDN = GND 1 µA

Quiescent Current (Not Switching) FB = –0.05V 40 50 µA

IFB Line Regulation 2.5V ≤ VIN ≤ 16V 0.07 %/V

Switch Off-Time 300 ns

Switch Current Limit LT3483

LT3483A

170

340

200

400

230

460

Switch VCESAT ISW = 150mA to GND 200 mV

Switch Leakage Current SW = 40V 1 µA

D Pin Current Limit 350 mA

Rectiﬁer Leakage Current D = – 40V 4 µA

Rectiﬁer Forward Drop ID = 150mA to GND 0.64 V

SHDN Input Low Voltage 0.4 V

SHDN Input High Voltage 1.5 V

SHDN Pin Current 6 10 µA

Note 2: The LT3483E/LT3483AE are guaranteed to meet speciﬁcations from

0°C to 85°C. Speciﬁcations over the –40°C to 85°C operating temperature

range are assured by design, characterization and correlation with

statistical process controls. The LT3483I/LT3483AI are guaranteed to meet

speciﬁcations over the –40°C to 125°C operating temperature range.

Note 3: Current ﬂows out of the pin.

LT3483/LT3483A

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TYPICAL PERFORMANCE CHARACTERISTICS

VFB Current

VFB Voltage

Switch Off Time

Switch Current Limit (LT3483)

Quiescent Current

SHDN Pin Bias Current

TEMPERATURE (°C)

–50

VFB CURRENT (µA)

10.0

10.1

75 100

3483 G01

9.9

9.8 –25 0 25 50 125

10.2

TEMPERATURE (°C)

–50

VFB VOLTAGE (mV)

75 100

3483 G02

0–25 0 25 50 125

TEMPERATURE (°C)

–50

SWITCH OFF TIME (ns)

150

200

250

50 125

3483 G03

100

0–25 0 25 75 100

300

350

400

TEMPERATURE (°C)

–50

170

SWITCH CURRENT LIMIT (mA)

180

190

200

210

220

230

–25 0 25 50 75 100

3483 G04

125

TEMPERATURE (°C)

–50

QUIESCENT CURRENT (µA)

75 100

3483 G05

0–25 0 25 50 125

SHDN PIN VOLTAGE (V)

SHDN PIN BIAS CURRENT (µA)

3483 G06

04812

10 TA = 25°C

Switch Current Limit (LT3483A)

TEMPERATURE (°C)

–50

CURRENT LIMIT (mA)

400

420

75 100

3483 G07

380

360 –25 0 25 50 125

440

LT3483/LT3483A

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PIN FUNCTIONS

FB (Pin 1/Pin 3): Feedback. Place resistor to negative

output here. Set resistor value R1 = VOUT/10µA.

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 1µF or greater.

NC (Pin 6/NA): No Internal Connection.

(Pin 7/Pin 5)

: Anode Terminal of Integrated Schottky

Diode. Connect to negative terminal of transfer capaci-

tor 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.

(DFN/TSOT-23)

BLOCK DIAGRAM

–

300ns

DELAY

1.250V

REFERENCE

20mV

(LT3483)

SW D

L1BL1A

CF LY COUT

VOUT

0.1Ω 0.1Ω

GND

3483 BD

–

25mV

R Q

125k

VOUT

VIN

OPTIONAL CHARGE PUMP CONFIGURATION.

L1B REPLACED WITH:

PIN NUMBERS CORRESPOND TO THE

6-PIN TSOT-23 PACKAGE

VOUT

• •

LT3483/LT3483A

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OPERATION

CHOOSING A REGULATOR TOPOLOGY

Inverting Charge Pump

The inverting charge pump regulator combines an induc-

tor-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/LT3483A 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/LT3483A. The

purpose of this resistor is to smooth/reduce the current

spike in the ﬂying capacitor when the switch turns on. A

10Ω 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 condi-

tion 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 pro-

prietary technique limits the switch current and prevents

damage to the LT3483/LT3483A even with supply voltage

as high as 16V. As an option, a 0.47µF capacitor may be

added between terminals D and SW of LT3483/LT3483A

to suppress ringing at SW.

Inductor Selection

Several recommended inductors that work well with the

LT3483/LT3483A 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 differ-

ent sizes and shapes are available. For inverting charge

pump regulators with input and output voltages below

7V, a 4.7µH or 6.8µH 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 10µH inductor is usually the best choice. A

larger value inductor can be used to slightly increase the

available output current, but limit it to around twice the

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. 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 be-

gin to ramp up. Once the switch current reaches 200mA

(LT3483) or 400mA (LT3483A), 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 the switch current limit. 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

LT3483/LT3483A

3483fc

APPLICATIONS INFORMATION

value recommended, as too large of an inductance will

increase the output voltage ripple without providing much

additional output current.

Table 1. Recommended Inductors

PART

(µH)

MAX

IDC

(mA)

DCR

(Ω)

HEIGHT

(mm)

MANUFACTURER

LQH2MCN4R7M02L

LQH2MCN6R8M02L

LQH2MCN100M02L

4.7

6.8

300

255

225

0.84

1.0

1.2

0.95 Murata

www.murata.com

SDQ12

Coupled

Inductor

4.7

1.45

980

780

0.40

0.72

1.15

1.2 Cooper Electronics

Tech

www.cooperet.com

LPD3015

Coupled

Inductor

4.7

860

580

0.52

1.0

1.4 Coilcraft

www.coilcraft.com

Capacitor Selection

The small size and low ESR of ceramic capacitors make

them ideal for LT3483/LT3483A 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 volt-

age rating. Table 2 shows a list of several ceramic capaci-

tor manufacturers. Consult the manufacturers for more

detailed information on their entire selection of ceramic

capacitors.

A 4.7µF ceramic bypass capacitor on the VIN pin is rec-

ommended where the distance to the power supply or

battery could be more than a couple inches. Otherwise,

a 1µF is adequate.

A capacitor in parallel with feedback resistor R1 is recom-

mended 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 conﬁgura-

tions. 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 4.7µF to 10µF capacitor. The

inverting charge pump utilizes values ranging from 0.22µF

to 4.7µF. The following formula is useful to estimate the

output capacitor value needed:

COUT =L•ISW

–VOUT •∆VOUT

where ISW = 0.25A (LT3483) or ISW = 0.5A (LT3483A) and

∆VOUT = 30mV. The ﬂying capacitor in the inverting charge

pump conﬁguration ranges from 0.1µF to 0.47µF. 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 URL

AVX www.avxcorp.com

Kemet www.kemet.com

Murata www.murata.com

Taiyo Yuden www.tyuden.com

Setting the Output Voltage

The output voltage is programmed using one feedback

resistor according to the following formula:

R1=–VOUT

10µA

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 recom-

mended 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.

LT3483/LT3483A

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Suggested Layout (DFN)

for Inverting Charge Pump

APPLICATIONS INFORMATION

Board Layout Considerations

As with all switching regulators, careful attention must

be given to the PCB board layout and component place-

ment. 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 ca-

pacitor switches directions within a cycle. Always use a

ground plane under the switching regulator to minimize

interplane coupling.

Suggested Layout (SOT-23)

for Inverting Charge Pump

VIN

GND

SHDN

CF LY

COUT

3483 AI01

CIN

VOUT

VIN

GND

SHDN

COUT

CIN CF LY

3483 AI02

VOUT

TYPICAL APPLICATIONS

3.6V to –22V DC/DC Converter 3.6V to –22V Converter Efﬁciency and Power Loss

10µH

LT3483

4.7µF

0.1µF D1

VIN

30Ω

2.2M

C1: TAIYO YUDEN LMK316BJ475MD

C2: TAIYO YUDEN TMK107BJ104 (X5R)

C3: TAIYO YUDEN TMK316BJ105MD

D1: PHILIPS PMEG3002AEB

L1: MURATA LQH2MCN100K02L

1µF

5pF

3483 TA02a

VOUT

–22V

8mA

VIN

3.6V

SHDN

GND

LOAD CURRENT (mA)

0.1

EFFICIENCY (%)

POWER LOSS (mW)

EFFICIENCY

3483 TA02b

55 1

100

POWER

LOSS

0.1

1000

LT3483/LT3483A

3483fc

TYPICAL APPLICATIONS

3.6V to –8V DC/DC Converter

Low Proﬁle, Small Footprint Switching Waveform

10µH

LT3483

4.7µF

0.22µF D1

VIN

10Ω

806k

C1: MURATA GRM219R61A475KE34B

C2: TAIYO YUDEN LMK107BJ224

C3: MURATA GRM219R61C225KA88B

D1: PHILIPS PMEG2005EB

L1: MURATA LQH2MCN100K02L

5pF C3

2.2µF

3483 TA04a

VOUT

–8V

25mA

VIN

3.6V

SHDN

GND

3483 TA04b

ISW

100mA/DIV

VOUT

20mV/DIV

2µs/DIV

PACKAGE DESCRIPTION

DC Package

8-Lead Plastic DFN (2mm × 2mm)

(Reference LTC DWG # 05-08-1719 Rev A)

2.00 ±0.10

(4 SIDES)

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

0.40 ± 0.10

BOTTOM VIEW—EXPOSED PAD

0.64 ± 0.10

(2 SIDES)

0.75 ±0.05

R = 0.115

TYP

R = 0.05

TYP

1.37 ±0.10

(2 SIDES)

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

0.200 REF

0.00 – 0.05

(DC8) DFN 0409 REVA

0.23 ± 0.05

0.45 BSC

PIN 1 NOTCH

R = 0.20 OR

0.25 × 45°

CHAMFER

0.25 ± 0.05

1.37 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

0.64 ±0.05

(2 SIDES)

1.15 ±0.05

0.70 ±0.05

2.55 ±0.05

PACKAGE

OUTLINE

0.45 BSC

LT3483/LT3483A

3483fc

PACKAGE DESCRIPTION

S6 Package

6-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1636 Rev B)

1.50 – 1.75

(NOTE 4)

2.80 BSC

0.30 – 0.45

6 PLCS (NOTE 3)

DATUM ‘A’

0.09 – 0.20

(NOTE 3) S6 TSOT-23 0302 REV B

2.90 BSC

(NOTE 4)

0.95 BSC

1.90 BSC

0.80 – 0.90

1.00 MAX 0.01 – 0.10

0.20 BSC

0.30 – 0.50 REF

PIN ONE ID

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

3.85 MAX

0.62

MAX

0.95

REF

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

1.4 MIN

2.62 REF

1.22 REF

LT3483/LT3483A

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 representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

C 09/10 Revised entire data sheet to add LTC3483A 1-12

(Revision history begins at Rev C)

LT3483/LT3483A

3483fc

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

 LINEAR TECHNOLOGY CORPORATION 2004

LT 0910 REV C • PRINTED IN USA

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DFN Package

L1A

4.7µH

L1B

4.7µH

LT3483A

4.7µF

• •

VIN

511k

22pF C2

10µF

3483 TA03a

VOUT

–5V

VIN

2.5V TO 6V

SHDN

GND

C1: TAIYO YUDEN EMK316BJ475ML

C2: TAIYO YUDEN JMK316BJ106ML

L1A, L1B: COILTRONICS SDQ12-4R7 OR

COILCRAFT LPD3015-472

LOAD CURRENT (mA)

0.1

EFFICIENCY (%)

POWER LOSS (mW)

1 10 100

3483 TA03b

120

150

180

210

VIN = 3.6V

Switching Waveforms

3483 TA03c

VSW

10V/DIV

IL1A

0.5A/DIV

IL1B

0.5A/DIV

VOUT

50mV/DIV

AC-COUPLED

2µs/DIV