Linear Technology LTC1503-2, LTC1503-1.8 Datasheet

1

LTC1503-1.8/LTC1503-2

High Efficiency Inductorless

Step-Down DC/DC Converters

■

Input Voltage Range: 2.4V to 6V

■

Fixed Output Voltages: 1.8V ±4%, 2V ±4%

■

Output Current: Up to 100mA

■

No Inductors

■

Typical Efficiency 25% Higher than LDOs

■

Low Operating Current: 25µA

■

Low Shutdown Current: 5µA

■

600kHz Switching Frequency

■

Shutdown Disconnects Load from V

IN

■

Soft-Start Limits Inrush Current at Turn-On

■

Short-Circuit and Overtemperature Protected

■

Available in 8-Pin MSOP and SO Packages

The LTC®1503-1.8/LTC1503-2 are switched capacitor
step-down DC/DC converters that produce a regulated
output from a 2.4V to 6V input. The parts use switched
capacitor fractional conversion to achieve high efficiency
over the entire input range. No inductors are required.
Internal circuitry controls the step-down conversion ratio
to optimize efficiency as the input voltage and load condi­tions vary. Typical efficiency is 25% higher than that of a
low dropout (LDO) linear regulator.

Regulation is achieved by sensing the output voltage and
enabling the internal switching network as needed to
maintain a fixed output voltage. This method of regulation
enables the parts to achieve high efficiency at extremely
light loads. Low operating current (25µA with no load, 5µA
in shutdown) and low external parts count (two 1µF flying
capacitors and two 10µF bypass capacitors) make the
LTC1503-1.8/LTC1503-2

ideally suited for space con­strained battery-powered applications. The parts are fully
short-circuit and overtemperature protected.

The

LTC1503-1.8/

LTC1503-2 are available in 8-pin MSOP

and SO packages.

, LTC and LT are registered trademarks of Linear Technology Corporation.

■

Cellular Phones

■

Handheld Computers

■

Smart Card Readers

■

Low Power DSP Supplies

■

Portable Electronic Equipment

■

Handheld Medical Instruments

Efficiency vs Input Voltage

Single Li-Ion to 2V DC/DC Converter

FEATURES

DESCRIPTIO

U

APPLICATIO S

U

TYPICAL APPLICATIO

U

4

2

3

5

1

8

6

7

V

IN

C1

–

C1

+

SHDN/SS

V

OUT

C2

–

C2

+

GND

LTC1503-2

1µF

1503-1.8/2 TA01

1µF

10µF

1-CELL Li-Ion OR

3-CELL NiMH

10µF

V

OUT

= 2V

I

OUT

= 100mA

INPUT VOLTAGE (V)

2

EFFICIENCY (%)

60

80

6

1503-1.8/2 TA02

40

20

3

4

5

100

LTC1503-2
V

OUT

= 2V

I

OUT

= 100mA

I

OUT

= 1mA

“IDEAL” LDO

2

LTC1503-1.8/LTC1503-2

Industrial Temperature Range ............... –40°C to 85°C

Specified Temperature Range (Note 2)... – 40°C to 85°C

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

Lead Temperature (Soldering, 10 sec)................. 300°C

(Note 1)

PARAMETER CONDITIONS MIN TYP MAX UNITS

VIN Operating Voltage ● 2.4 6 V
V

OUT

LTC1503-1.8, 0mA < I

OUT

< 100mA ● 1.728 1.8 1.872 V

LTC1503-2, 0mA < I

OUT

< 100mA ● 1.920 2.0 2.080 V

VIN Operating Current I

OUT

= 0mA ● 25 50 µA

VIN Shutdown Current SHDN/SS = 0V ● 510 µA
Output Ripple Voltage LTC1503-X, VIN = 3.6V, I

OUT

= 100mA 25 mV

P-P

Efficiency LTC1503-2, VIN = 3.6V, I

OUT

= 100mA 82.9 %

Switching Frequency Oscillator Free Running 600 kHz
SHDN/SS Input Threshold ● 0.2 0.35 0.5 V
SHDN/SS Input Current V

SHDN/SS

= 0V (Note 3) ● –3.5 –2 –1 µA

V

SHDN/SS

= V

IN

● –1 1 µA

V

OUT

Short-Circuit Current V

OUT

= 0V (Note 4) ● 82250 mA

V

OUT

Turn-On Time CSS = 0nF, VIN = 3.6V, C

OUT

= 10µF 0.1 ms

C

SS

= 10nF 8 ms

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: The LTC1503C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but are not tested at –40°C and 85°C. The
LTC1503I is guaranteed to meet the extended temperature limits.

Note 3: Currents flowing into the device are positive polarity. Currents
flowing out of the device are negative polarity.

Note 4: When V

OUT

is less than 150mV, I

OUT

is limited to much less than
the maximum rated output current to prevent damage to the output
devices.

ORDER PART

NUMBER

LTC1503CMS8-1.8
LTC1503CMS8-2

MS8 PART MARKING

LTFX
LTHN

ORDER PART

NUMBER

LTC1503CS8-1.8
LTC1503CS8-2
LTC1503IS8-1.8
LTC1503IS8-2

S8 PART MARKING

150318
15032

Consult factory for Military grade parts.

T

JMAX

= 125°C, θJA = 200°C/W

1
2
3
4

V

OUT

C1

–

C1

+

V

IN

8
7
6
5

C2

–

GND
C2

+

SHDN/SS

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP

T

JMAX

= 125°C, θJA = 150°C/W

1

2

3

4

8

7

6

5

TOP VIEW

S8 PACKAGE

8-LEAD PLASTIC SO

V

OUT

C1

–

C1

+

V

IN

C2

–

GND
C2

+

SHDN/SS

VIN, C1+, C1–, C2+, C2– to GND............... –0.3V to 6.5V

SHDN/SS to GND......................... –0.3V to (VIN + 0.3V)

V

OUT

Short-Circuit Duration............................. Indefinite

Commercial Temperature Range ............ –40°C to 85°C

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = V

IN(MIN)

to V

IN(MAX)

, C1 = C2 = 1µF, CIN = C

OUT

= 10µF unless otherwise noted.

503I18
1503I2

ABSOLUTE AXI U RATI GS

WWWU

PACKAGE/ORDER I FOR ATIO

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ELECTRICAL CHARACTERISTICS

3

LTC1503-1.8/LTC1503-2

LTC1503-X Input Operating
Current vs Input Voltage

INPUT VOLTAGE (V)

2

INPUT CURRENT (µA)

30

T

A

= 25°C

40

6

1503 G01

20

10

3

4

5

50

I

OUT

= 0mA

TA = –40°C

T

A

= 85°C

LTC1503-1.8
Output Voltage vs Input Voltage

LTC1503-2
Output Voltage vs Input Voltage

LTC1503-1.8
Efficiency vs Input Voltage

INPUT VOLTAGE (V)

2

OUTPUT VOLTAGE (V)

2.00

2.05

6

1503 G03

1.95

1.90
3

4

5

2.10

I

OUT

= 50mA

TA = –40°C

T

A

= 85°C

T

A

= 25°C

INPUT VOLTAGE (V)

2

EFFICIENCY (%)

60

80

6

1503-1.8/2 G05

40

20

3

4

5

100

“IDEAL”

LDO

TA = 25°C

I

OUT

= 100mA

I

OUT

= 1mA

LTC1503-1.8
Efficiency vs Output Current

LTC1503-X Input Shutdown
Current vs Input Voltage

INPUT VOLTAGE (V)

2

INPUT SHUTDOWN CURRENT (µA)

5

7.5

6

1503-1.8/2 TA02

2.5

0

3

4

5

10

V

OUT

= 0V

V

SHDN

/SS = 0V

TA = –40°C

T

A

= 85°C

T

A

= 25°C

INPUT VOLTAGE (V)

2

OUTPUT VOLTAGE (V)

1.80

1.85

6

1503-1.8/2 G03

1.75

1.70
3

4

5

1.90

I

OUT

= 50mA

TA = –40°C

T

A

= 85°C

TA = 25°C

OUTPUT CURRENT (mA)

0.01

EFFICIENCY (%)

60

80

100

100

1503-1.8/2 G06

40

20

0

0.1

1

10

1000

VIN = 5V
V

IN

= 4.4V

V

IN

= 3.6V

V

IN

= 3V

V

IN

= 2.4V

TA = 25°C

LTC1503-2
Efficiency vs Output Current

OUTPUT CURRENT (mA)

0.01

EFFICIENCY (%)

60

80

100

100

1503-1.8/2 G07

40

20

0

0.1

1

10

1000

VIN = 5V
V

IN

= 4.4V

V

IN

= 3.6V

V

IN

= 3V

V

IN

= 2.4V

TA = 25°C

LTC1503-1.8
Output Voltage vs Output Current

OUTPUT CURRENT (mA)

0.01

OUTPUT VOLTAGE (V)

1.80

1.82

1.84

100

1503-1.8/2 G08

1.78

1.76

1.74

0.1

1

10

1000

VIN = 3.3V

TA = –40°C

TA = 85°C

T

A

= 25°C

LTC1503-2
Output Voltage vs Output Current

OUTPUT CURRENT (mA)

0.01

OUTPUT VOLTAGE (V)

2.00

2.02

2.04

100

1503-1.8/2 G09

1.98

1.96

1.94

0.1

1

10

1000

VIN = 3.3V

TA = –40°C

TA = 85°C

T

A

= 25°C

TYPICAL PERFOR A CE CHARACTERISTICS

UW

4

LTC1503-1.8/LTC1503-2

TYPICAL PERFOR A CE CHARACTERISTICS

UW

LTC1503-X Output Short-Circuit
Current vs Input Voltage

LTC1503-X Start-Up Time
vs Soft-Start Capacitor

INPUT VOLTAGE (V)

2

OUTPUT CURRENT (mA)

20

30

6

1503-1.8/2 G10

10

0

3

4

5

40

V

OUT

SHORTED TO GND

TA = –40°C

TA = 85°C

T

A

= 25°C

SOFT-START CAPACITOR (nF)

0.01

START-UP TIME (ms)

1

10

100

1503-1.8/2 G10

0.1

0.01

0.1

1

10

100

VIN = 3.6V

TA = –40°C

TA = 25°C

TA = 85°C

Output Load Transient Response
(LTC1503-1.8,1mA to 100mA Step)

I

OUT

50mA/DIV

V

OUT

50mV/DIV

AC COUPLED

100mA

1mA

1ms/DIV

1503-1.8/2 G12

Output Ripple, C

OUT

= 10µF

V

OUT

10mV/DIV

AC COUPLED

5µs/DIV

1503-1.8/2 G13

VIN = 3.6V
V

OUT

= 2V

I

OUT

= 100mA

C

OUT

= 10µF CERAMIC

Output Ripple, C

OUT

= 22µF

V

OUT

10mV/DIV

AC COUPLED

5µs/DIV

1503-1.8/2 G14

VIN = 3.6V
V

OUT

= 2V

I

OUT

= 100mA

C

OUT

= 22µF CERAMIC

V

OUT

(Pin 1): Regulated Output Voltage. V

OUT

is discon-

nected from VIN during shutdown. Bypass V

OUT

to ground

with a ≥10µF low ESR capacitor.

C1– (Pin 2): Flying Capacitor One Negative Terminal.
C1+ (Pin 3): Flying Capacitor One Positive Terminal.
VIN (Pin 4): Input Voltage. VIN may be between 2.4V and

6V. Bypass VIN to ground with a ≥10µF low ESR capacitor.
SHDN/SS (Pin 5): Shutdown/Soft-Start Control. The pin

is designed to be driven with an external open-drain

output. Holding the SHDN/SS pin below 0.25V will force
the part into shutdown mode. An internal pull-up current
of 2µA will force the SHDN/SS voltage to climb to VIN once
the device driving the pin is forced into a Hi-Z state. To
limit inrush current on start-up, connect a capacitor
between the SHDN/SS pin and ground. Capacitance on
the SHDN/SS pin will limit the dV/dt of the pin during turn­on which, in turn, will limit the dV/dt of V

OUT

. By selecting
an appropriate soft-start capacitor for a known output
capacitor, the user can control the inrush current during

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