Datasheet LT1300 Datasheet (Linear Technology)

3.3/5V Step-Up DC/DC Converter

FEATURES

■

Up to 220mA Output Current at 5V from 2V Supply

■

Supply Voltage as Low as 1.8V

■

Up to 88% Efficiency

■

Small Inductor –10µH

■

120µA Quiescent Current

■

Shutdown to 10µA

■

Programmable 3.3V or 5V Output

■

I

Pin Programs Peak Switch Current

LIM

■

Low V

■

Uses Inexpensive Surface Mount Inductors

■

8-Lead DIP or SOIC Package

Switch: 170mV at 1A Typical

CESAT

U

APPLICATIONS

■

Palmtop Computers

■

Portable Instruments

■

Bar-Code Scanners

■

DC/DC Converter Module Replacements

■

Battery Backup Supplies

■

Personal Digital Assistants

■

PCMCIA Cards

LT1300

Micropower High Efficiency

U

DESCRIPTION

The LT1300 is a micropower step-up DC/DC converter that
utilizes Burst Mode™ operation. The device can deliver 5V
or 3.3V from a two-cell battery input. It features program­mable 5V or 3.3V output via a logic-controlled input, no­load quiescent current of 120µ A and a shutdown pin which
reduces supply current to 10µ A. The on-chip power switch
has a low 170mV saturation voltage at a switch current of
1A, a four-fold reduction over prior designs. A 155kHz
internal oscillator allows the use of extremely small sur­face mount inductors and capacitors. Operation is guaran­teed at 1.8V input. This allows more energy to be extracted
from the battery increasing operating life. The I
be used to program peak switch current with a single
resistor allowing the use of less expensive and smaller
inductors and capacitors in lighter load applications. The
LT1300 is available in an 8-lead SOIC package, minimizing
board space requirements. For a 5V/12V Selectable Out­put Converter see the LT1301. For increased output cur­rent see the LT1302.

Burst Mode is a trademark of Linear Technology Corporation.

LIM

pin can

U

TYPICAL APPLICATIONS N

Two-Cell to 3.3V/5V Step-Up Converter 5V Output Efficiency

L1

10µH D1

5V/3.3V

2×
AA
CELL

L1 = COILCRAFT DO1608-103

OR SUMIDA CD54-100

C1 = AVX TPSD107M010R0100

OR SANYO OS-CON 16SA100M

D1 =MBRS130LT3

OR 1N5817

SELECT

+

C1
100µF

SHUTDOWN

67

V

IN

2

SELECT

LT1300

3

SHDN

PGND

81

SW

SENSE

I

LIM

GND

4



5

N/C

+

C1
100µF


5V/3.3V
OUTPUT

LT1300 TA1

90

88

86

84

82

80

EFFICIENCY (%)

78

76

74

1

VIN = 4.0V

VIN = 3.0V

VIN = 2.5V

VIN = 2.0V

10 100 500

LOAD CURRENT (mA)

LT1300 TA2

1

LT1300

WW

W

ABSOLUTE MAXIMUM RATINGS

VIN Voltage .............................................................. 10V

SW1 Voltage ............................................................ 20V

Sense Voltage .......................................................... 10V

SHUTDOWN Voltage................................................ 10V

SELECT Voltage ....................................................... 10V

I

Voltage ............................................................ 0.5V

LIM

Maximum Power Dissipation ............................. 500mW

Operating Temperature Range ..................... 0°C to 70°C

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

U

U

W

PACKAGE/ORDER INFORMATION

TOP VIEW

GND

1

SEL

2

SHDN

3

SENSE

4

N8 PACKAGE

8-LEAD PLASTIC DIP



T

= 100°C, θJA = 150°C/W

JMAX

PGND

8

SW

7

V

6

IN

I

5

LIM



S8 PACKAGE

8-LEAD PLASTIC SOIC



ORDER PART

NUMBER

LT1300CN8
LT1300CS8

S8 PART MARKING

1300

U

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

Consult factory for Industrial grade parts.

SEL

= 5V, V

TA = 25°C, V

SENSE

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

Q

VINInput Voltage Range 1.8 V

V

OUT

DC Maximum Duty Cycle 75 86 95 %
t

ON

V

CESAT

V

SHDNH

V

SHDNL

V

SELH

V

SELL

I

SHDN

I

SEL

The
temperature range.

Quiescent Current V

Output Sense Voltage V

Output Referred V
Comparator Hysteresis V

Oscillator Frequency Current Limit not Asserted. See Test Circuit. 120 155 185 kHz
Oscillator TC 0.2 %/°C

Switch On Time Current Limit not Asserted. 5.6 µs
Output Line Regulation 1.8V < VIN < 6V ● 0.06 0.15 %/V
Switch Saturation Voltage ISW = 700mA ● 130 200 mV
Switch Leakage Current VSW = 5V, Switch Off ● 0.1 10 µA
Peak Switch Current I

(Internal Trip Point) I
Shutdown Pin High ● 1.8 V
Shutdown Pin Low 0.5 V
Select Pin High ● 1.5 V
Select Pin Low ● 0.8 V
Shutdown Pin Bias Current V

Select Pin Bias Current 0V < V

● denotes specifications which apply over the 0°C to 70°C

= 0.5V, V

SHDN

V

= 1.8V ● 715 µA

SHDN

= 5V ● 4.80 5.0 5.20 V

SEL

V

= 0V ● 3.15 3.3 3.45 V

SEL

= 5V (Note 1) ● 22 50 mV

SEL

= 0V (Note 1) ● 14 35 mV

SEL

Floating (See Typical Application) 0.75 1.0 1.25 A

LIM

Grounded 0.4 A

LIM

= 5V ● 920 µA

SHDN

= 2V ● 3 µA

V

SHDN

V

= 0V ● 0.1 1 µA

SHDN

< 5V ● 13 µA

SEL

= 2V unless otherwise noted.

IN

= 5.5V ● 120 200 µA

● 2.0 V

Note 1: Hysteresis specified is DC. Output ripple may be higher if
output capacitance is insufficient or capacitor ESR is excessive. See
applications section.

2

W

INPUT VOLTAGE (V)

0

I

SHDN

+ I

VIN

+ I

SENSE

(µA)

40

50

60

8

LT1300 G3

30

20

0

2

4

6

10

80

70

1

3

5

7

INPUT VOLTAGE (V)

1.5

OUTPUT CURRENT (mA)

500

600

700

34

LT1300 G6

400

300

2

2.5

3.5 4.5

200

100

0

V

OUT

= 5V,

I

LIM

FLOATING

L = 22µH

COILCRAFT

DO3316-223

L = 10µH
COILCRAFT
DO1608-103

U

TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency

88

V

= 3.3V

OUT

86

L = 10µH

84
82

VIN = 3V

80
78
76
74

EFFICIENCY (%)

72
70
68
66

1

VIN = 2.5V

10 100 1000

LOAD CURRENT (mA)

Shutdown Pin Bias Current

20

T

= 25°C

A

18
16
14
12
10

8
6

SHUTDOWN CURRENT (µA)

4
2
0

0

13

2

SHUTDOWN VOLTAGE (V)

VIN = 2V

4

5

LT1300 G1

7

6

LT1300 G4

8

No-Load Battery Current

170
165

160
155

150
145

140
135

INPUT CURRENT (µA)

130
125
120

250
225

200
175

150

(mV)

125

CESAT

100

V

75

50
25

1.4

V

0

CESAT

0 0.1

V

= 5V

OUT

V

= 3.3V

OUT

1.81.6

2.22.0

INPUT VOLTAGE (V)

vs I

SW

0.2 0.3

0.4 0.5

SWITCH CURRENT (A)

2.62.4

0.6 0.7

3.02.8

0.8 0.9

LT1300

Total Quiescent Current
in Shutdown

3.43.2

LT1300 G2

Maximum Output Current
vs Input Voltage

1

LT1300 G5

Maximum Output Current
vs Input Voltage

900

800

700

600

500

400

300

LOAD CURRENT (mA)

200

100

0

1.5

V

= 3.3V

OUT

I

FLOATING

LIM

L = 10µH

2

2.5

INPUT VOLTAGE (V)

Transient Response
VIN = 2V, V

V

OUT

100mV/DIV

AC COUPLED

200mA

I

LOAD

0

3.5

3

LT1300 G7

OUT

200µs/DIV

= 5V

LT1300 G8

Startup Response

V

OUT

1V/DIV

V

SHDN

10V/DIV

V

= 5V

OUT

= 20Ω

R

LOAD

500µs/DIV

LT1300 G9

3

LT1300

PIN FUNCTIONS

UUU

GND (Pin 1): Signal Ground.
Sel (Pin 2): Output Select. When tied to VIN or V

OUT

converter regulates at 5V. When grounded converter
regulates at 3.3V.

SHDN (Pin 3): Shutdown. Pull high to effect shutdown. Tie
to ground for normal operation.

Sense (Pin 4): “Output” Pin.
I

(Pin 5): Float for 1A switch current limit. Tie to ground

LIM

for approximately 400mA. A resistor between I

LIM

and
ground sets peak current to some intermediate value (see
Figure 5).

W

BLOCK DIAGRAM

V

IN

+

C1

VIN (Pin 6): Supply Pin. Must be bypassed with a large
value electrolytic to ground. A 0.1µF ceramic capacitor
close to the pin may be needed in some cases.

SW (Pin 7): Switch Pin. Connect inductor and diode here.
Keep layout short and direct to minimize electronic radia­tion.

PGND (Pin 8): Power Ground. Tie to signal ground (pin 1)
under the package. Bypass capacitor from VIN should be
tied directly to the pin.

L1

D1

V

OUT

+

C2



1.25V

REFERENCE

SENSE

4

144k

GND

1

500k

161k

SELECT

2

A1
COMPARATOR

+

–

ENABLE

Figure 1.

V

IN

2

OSCILLATOR

155kHZ

SHUTDOWN

3

A2 CURRENT 

COMPARATOR

OFF



A3 DRIVER

BIAS

SW

7

18mV

R2

730Ω

R1
3Ω

+

–

Q1

Q2

160x

1x

Q3

8.5k
I

LIM

58

PGND

LT1300 F1

4

S



TEST CIRCUIT

LT1300

Oscillator Test Circuit

2V

SEL

V

IN

I

L

SW

5V

100Ω

f

OUT

100µF

LT1300

SENSE

GND PGND

U

OPERATION

Operation of the LT1300 is best understood by referring to
the Block Diagram in Figure 1. When A1’s negative input,
related to the Sense pin voltage by the appropriate resis­tor-divider ratio, is higher that the 1.25V reference voltage,
A1’s output is low. A2, A3 and the oscillator are turned off,
drawing no current. Only the reference and A1 consume
current, typically 120µA. When the voltage at A1’s nega-
tive input decreases below 1.25V, overcoming A1’s 6mV
hysteresis, A1’s output goes high, enabling the oscillator,
current comparator A2, and driver A3. Quiescent current
increases to 2mA as the device prepares for high current
switching. Q1 then turns on in a controlled saturation for
(nominally) 5.3µs or until current comparator A2 trips,
whichever comes first. After a fixed off-time of (nominally)

1.2µ s, Q1 turns on again. The LT1300’s switching causes
current to alternately build up in L1 and dump into capaci­tor C2 via D1, increasing the output voltage. When the
output is high enough to cause A1’s output to go to low,
switching action ceases. C2 is left to supply current to the
load until V
high, and the entire cycle repeats.

If switch current reaches 1A, causing A2 to trip, switch on­time is reduced and off-time increases slightly. This allows
continuous mode operation during bursts. Current com­parator A2 monitors the voltage across 3Ω resistor R1
which is directly related to inductor L1’s current. Q2’s
collector current is set by the emitter-area ratio to 0.6%
of Q1’s collector current. When R1’s voltage drop exceeds
18mV, corresponding to 1A inductor current, A2’s output
goes high, truncating the on-time portion of the oscillator
cycle and increasing off-time to about 2µs as shown in
Figure 2, trace A. This programmed peak current can be

decreases enough to force A1’s output

OUT

SHDN

TRACE A

500mA/DIV

PIN

I

LIM

OPEN

TRACE B

500mA/DIV

PIN

I

LIM

GROUNDED

20µs/DIV

Figure 2. Switch Pin Current With I

reduced by tying the I

pin to ground, causing 15µA to

LIM

Floating or Grounded

LIM

LT1300 F2

flow through R2 into Q3’s collector. Q3’s current causes
a 10.4mV drop in R2 so that only an additional 7.6mV is
required across R1 to turn off the switch. This corre­sponds to a 400mA switch current as shown in Figure 2,
trace B. The reduced peak switch current reduces I2R
loses in Q1, L1, C1 and D1. Efficiency can be increased by
doing this provided that the accompanying reduction in
full load output current is acceptable. Lower peak currents
also extend alkaline battery life due to the alkaline cell’s
high internal impedance. Typical operating waveforms are
shown in Figure 3.

V

OUT

20mV/DIV

AC COUPLED

V

SW

5V/DIV

I

SW

IA/DIV

20µS/DIV

Figure 3. Burst Mode Operation in Action

LT1300 F2

5

LT1300

U

WUU

APPLICATIONS INFORMATION

Output Voltage Selection

The LT1300 can be selected to 3.3V or 5V under logic
control or fixed at either by tying SELECT to ground or V
respectively. It is permissible to tie SELECT to a voltage
higher than VIN as long as it does not exceed 10V.
Efficiency in 3.3V mode will be slightly less that in 5V mode
due to the fact that the diode drop is a greater percentage
of 3.3V than 5V. Since the bipolar switch in the LT1300
gets its base drive from VIN, no reduction in switch
efficiency occurs when in 3.3V mode. When VIN exceeds
the programmed output voltage the output will follow the
input. This is characteristic of the simple step-up or
“boost” converter topology. A circuit example that pro­vides a regulated output with an input voltage above or
below the output (called a buck-boost or SEPIC) is shown
in the Typical Applications section.

Shutdown

The converter can be turned off by pulling SHDN (pin 3)
high. Quiescent current drops to 10µA in this condition.
Bias current of 3µA to 5µ A flows into the pin (at 2.5V input).
It is recommended that SHDN not be left floating. Tie the
pin to ground if the feature is not used.

IN

L1

10µH

V

IN

+

SELECT
C1
100µF

SHDN

PGND GND

LT1300

SW

SENSE

I

LIM

R1
1M

D1

5V/3.3V
OUTPUT

+

C2
100µF


C3

0.1µF


Figure 4. Addition of R1 and C3 Limit Input Current at Startup

V

OUT

2VDIV

I

BATTERY

500mA/DIV

V

SHDN

10V/DIV

500µs/DIV

REP RATE = 1Hz

LT1300 F5

I

Function

LIM

The LT1300’s current limit (I

) pin can be used for soft

LIM

start. Upon start-up, switching regulators require maxi­mum current from the supply. The high currents flowing
can create IR drops along supply and ground lines and
are especially demanding on alkaline batteries. By in­stalling an R1 and C3 as shown in Figure 4, the switch
current in the LT1300 is limited to 400mA until the 15µ A
flowing out of the I

pin charges up the 0.1µ F capaci-

LIM

tor. Input current is held to under 500mA while the
output voltage ramps up to 5V as shown in Figure 5. The
1Meg resistor provides a discharge path for the capacitor
without appreciably decreasing peak switch current. When
the full capability of the LT1300 is not required, peak
current can be reduced by changing the value of R3 as
shown in Figure 6. With R3 = 0, switch current is limited
to approximately 400mA.

Figure 5. Startup Waveforms using Soft-Start Circuitry

I

= 100mA, V

LOAD

1100

1.6V ≤ VIN ≤ 5V

1000

900

800

700

600

SWITCH CURRENT (mA)

500

400

300

100 10k 100k 1M

1k

Figure 6. Peak Switch Current vs. R

R

OUT

LIM

= 5V

(Ω)

LT1300 F1B

LIM

6

LT1300

U

WUU

APPLICATIONS INFORMATION

Table 1. Recommended Inductors

EFFICIENCY 2.5VIN, 5V

PART NUMBER VENDOR L (µH) DCR (Ω)I

DO1608-103 Coilcraft 10 0.11 Float 83 83 3.5 (708) 639–6400
DO3316-223 Coilcraft 22 0.050 Float 85 85 5.5
DO1608-223 Coilcraft 22 0.31 Ground 85 — 3.5
CTX10-1 Coiltronics 10 0.038 Float 85 85 4.2 (407) 241–7876
CTX20-1 Coiltronics 20 0.175 Ground 86 — 4.2
LQH3C2204K0M00 Murata-Frie 22 0.7 Ground 81 — 2.0 (404) 436–1300
CD54-100M Sumida 10 0.11 Float 85 85 4.5 (708) 956–0666
CDRH62-220M Sumida 22 0.38 Ground 84 — 3.0
CDRH62-100M Sumida 10 0.17 Float 81 82 3.0
GA10-102K Gowanda 10 0.038 Float 85 86 6.6 Through-Hole (716) 532–2234

Inductor Selection

For full output power, the inductor should have a satura­tion current rating of 1.25A for worst-case current limit,
although it is acceptable to bias an inductor 20% or more
into saturation. Smaller inductors can be used in conjunc­tion with the I

pin. Efficiency is significantly affected by

LIM

inductor DCR. For best efficiency limit the DCR to 0.03Ω
or less. Toroidal types are preferred in some cases due to
their closed design and inherent EMI/RFI superiority.
Recommended inductors are listed in Table 1.

PIN 50mA LOAD 200mA LOAD HEIGHT (mm) PHONE NUMBER

LIM

Table 2. Recommended Capacitors

VENDOR SERIES TYPE PHONE#

AVX TPS Surface Mount (803)448–9411
Sanyo OS-CON Through-Hole (619) 661–6835
Panasonic HFQ Through-Hole (201) 348–5200

Diode Selection

Best performance is obtained with a Schottky rectifier
diode such as the 1N5817. Phillips Components makes
this in surface mount as the PRLL5817. Motorola makes
the MBRS130LT3 which is slightly better and also in

Capacitor Selection

Low ESR capacitors are required for both input and output

surface mount. For lower output power a 1N4148 can be
used although efficiency will suffer substantially.

of the LT1300. ESR directly affects ripple voltage and
efficiency. For surface mount applications AVX TPS series
tantalum capacitors are recommended. These have been
specially designed for SMPS and have low ESR along with
high surge current ratings. For through-hole application
Sanyo OS-CON capacitors offer extremely low ESR in a
small size. Again, if peak switch current is reduced using
the I

pin, capacitor requirements can be relaxed and

LIM

Layout Considerations

The LT1300 is a high speed, high current device. The input
capacitor must be no more than 0.2" from VIN (pin 6) and
ground. Connect the PGND and GND (pins 8 and 1)
together under the package. Place the inductor adjacent to
SW (pin 7) and make the switch pin trace as short as
possible. This keeps radiated noise to a minimum.

smaller, higher ESR units can be used. Low frequency
output ripple can be reduced by adding multiple output
capacitors. If capacitance is reduced, output ripple will
increase. Suggested capacitor sources are listed in Table 2.

OUT

COMPONENT

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.

7

LT1300

N8 0392

0.009 – 0.015

(0.229 – 0.381)

0.300 – 0.320

(7.620 – 8.128)

0.325

+0.025
–0.015

+0.635
–0.381

8.255

()

0.045 ± 0.015

(1.143 ± 0.381)

0.100 ± 0.010

(2.540 ± 0.254)

0.065

(1.651)

TYP

0.045 – 0.065

(1.143 – 1.651)

0.130 ± 0.005

(3.302 ± 0.127)

0.020

(0.508)

MIN

0.018 ± 0.003

(0.457 ± 0.076)

0.125

(3.175)

MIN



1234

876

5

0.250 ± 0.010

(6.350 ± 0.254)





0.400

(10.160)

MAX

+

100µF

22µF
35V

CONTRAST 
V

OUT

–4V TO –29V 12mA
MAXIMUM FROM 1.8V SUPPLY 
(77% EFFICIENT)
20mA MAXIMUM FROM 
3V SUPPLY (83% EFFICIENT)

2.2µF

SW

PWM IN

0% TO 100%

CMOS DRIVE 0V TO 5V

150K

12K

12K

1

10

8
2

9

3

7

4

I

LIM

PGND

GND

SENSE

LT1300

SELECT

LT1300 TA6

1N5819

T1

T1 = DALE LPE-5047-AO45 [phone]

SHDN

SHUTDOWN

N/C

N/C

V

IN

V

IN

1.8V TO 6V

+

+

U

TYPICAL APPLICATIONS N

Four-Cell to 5V/3.3V Up-Down Converter

C2**

L1*

≤ 8V

2.5V ≤ V

IN

4×
AA
CELL

+

5V/3.3V

C1**
100µF

SHUTDOWN

*L1, L2 = GOWANDA GA20-272K
COILCRAFT DO3316-273K
SUMIDA CD73-270K
**C1, C2, C3 = SANYO OS-CON 16SA100M

N/C

I

LIM

SELECT

SHDN

GND

LT1300

V

SENSE

PGND

IN

SW



27µH

100µF

+

L2*
27µH

Step-Up Converter with Automatic Output Disconnect

470Ω

L1*

1N5817

10µH

2×
AA
CELL

LT1300

V
SW

SENSE

PGND

IN



SELECT

SHUTDOWN

+

100µF

SHDN

I

NC

LIM

GND

+

100µF

+

LT1300 TA3

2N4403

1N5817

5V/3.3V
220mA
80% EFFICIENT

C3**
100µF

5V, 200mA

0.1µF

LCD Contrast Supply

*SUMIDA CD54-100LC 
COILCRAFT DO3316-223

PACKAGE DESCRIPTION

N8 Package

8-Lead Plastic DIP

S8 Package

8-Lead Plastic S0IC

8

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7487

[phone]

0.008 – 0.010

(0.203 – 0.254)

●

FAX

: [phone]

0.010 – 0.020

(0.254 – 0.508)

LT1300 TA5

U

Dimensions in inches (millimeters) unless otherwise noted.

0.016 – 0.050

0.406 – 1.270

× 45°

0°– 8° TYP

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).

●

TELEX

: 499-3977

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

0.004 – 0.010

(0.101 – 0.254)

0.050

(1.270)

BSC

0.189 – 0.197*
(4.801 – 5.004)

0.228 – 0.244

(5.791 – 6.197)

7

8

1

2

5

6

0.150 – 0.
(3.810 – 3.

3

4

SO8 0294

LT/GP 0394 10K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1994