Linear LT1317B, LT1317 Demo Manual

DEMO MANUAL DC194

MICROPOWER BOOST REGULATOR

LT1317/LT1317B

Micropower, 600kHz

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PWM DC/DC Converters

DESCRIPTIO

Demonstration Circuit DC194 is a micropower boost
regulator that converts an input as low as 1.5V to an output
of 3.3V or 5.0V. DC194 version A uses the LT®1317CMS8;
version B uses the LT1317BCMS8. This circuit provides
regulated power for battery-powered devices, such as
laptop and palmtop computers, cellular phones, pagers,
LCD panels and other portable devices. It is also useful for
local conversion of logic supplies, such as 3.3V to 5V
conversion in PC card devices.

The LT1317 and LT1317B are 600kHz PWM DC/DC con­verters. Their high operating frequency and small package

result in small, cost effective solutions. The micropower
LT1317 shifts automatically to low power Burst Mode
operation at light loads, whereas the LT1317B operates at
a fixed frequency at all loads. Both parts feature a low­battery detector that remains active while the part is shut
down. The wide voltage ratings (12V input and 30V
switch) make the LT1317 and LT1317B versatile parts,
suitable for implementing boost, flyback and SEPIC
topologies.

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

Burst Mode is a trademark of Linear Technology Corportion.

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PERFOR A CE SU ARY

PARAMETER CONDITIONS VALUE

Input Voltage (Note 1) V

Maximum Load Current, Min V

Shutdown Current, Typ VIN = 2.5V, SHDN = 0V 25µA
No Load Quiescent Current, Typ V

Note 1: This limit is based on the DC194 circuit. The LT1317 can operate
from high supply voltages.

= 3.3V 1.5V to 3.6V

OUT

V

= 5V 1.5V to 5.3V

OUT

= 3.3V, VIN = 1.6V 175mA

OUT

= 3.3V, VIN = 2.4V 320mA

V

OUT

= 5V, VIN = 2V 140mA

V

OUT

= 5V, VIN = 3.3V 290mA

V

OUT

= 3.3V, VIN = 2.4V, LT1317 125µA

OUT

= 3.3V, VIN = 2.4V, LT1317B 4.8mA

V

OUT

TM

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W

TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO

LT1317 Efficiency

90

VIN = 3V

80

LT1317
V

OUT

VIN = 1.6V

= 3.3V

1

LOAD CURRENT (mA)

70

60

EFFICIENCY (%)

50

40

0.3 10 100 1000

VIN = 2.4V

DC194 G04

LT1317 Efficiency

90

80

70

60

EFFICIENCY (%)

50

LT1317

= 5V

V

OUT

40

0.3 10 100 1000

1

VIN = 3.3V

VIN = 2.4V

VIN = 1.6V

LOAD CURRENT (mA)

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Board Photo

DC194 BP

DC194 G03

1

DEMO MANUAL DC194

LOAD CURRENT (mA)

1

EFFICIENCY (%)

90

80

70

60

50

40

10 100 1000

DC194 G05

LT1317B
V

OUT

= 5V

VIN = 3.3V

VIN = 1.6V

VIN = 2.4V

MICROPOWER BOOST REGULATOR

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TYPICAL PERFORMANCE CHARACTERISTICS

LT1317B Efficiency

90

LT1317B
V

OUT

80

70

60

EFFICIENCY (%)

50

40

1

= 3.3V

VIN = 3V

VIN = 2.4V

VIN = 1.6V

10 100 1000

LOAD CURRENT (mA)

Load Current vs Input Voltage

600

V

= 3.3V

OUT

500

400

300

OUTPUT CURRENT (mA)

200

TYPICAL

MINIMUM

DC194 G06

LT1317B Efficiency

Load Current vs Input Voltage

600

V

= 5V

OUT

500

400

300

OUTPUT CURRENT (mA)

200

TYPICAL

MINIMUM

100

1.5

2.0

2.5

INPUT VOLTAGE (V)

3.0

3.5

DC194 G01

W UW

PACKAGE A D SCHE ATIC DIAGRA SM

TOP VIEW

V

1



C

2

FB

3

SHDN

4

GND

MS8 PACKAGE

8-LEAD PLASTIC MSOP

NOTES:

1. FOR VERSION A: USE LT1317CMS8 (LTHA)

2. FOR VERSION B; USE LT1317BCMS8 (LTHB)

3. FOR 3.3V OUTPUT, INSTALL SHUNT AT
 JP1 PINS 1, 2
 FOR 5V OUTPUT, INSTALL SHUNT AT
 JP1 PINS 2, 3

8

LBO

7

LBI

6

V



IN

5

SW

SHDN

LBO

LT1317CMS8
LT1317BCMS8

V

IN

R7
OPT



LBI

R6
OPT

L1

10µH

R4
OPT

R5
OPT

+

C1
22µF
10V

3

7
8

C5

100pF

6

V

IN

LT1317CMS8(A)

SHDN
LBI

LT1317BCMS8(B)

LBO

V

C





1



R3
33k

C3
3300pF

LTHA

LTHB

Figure 1. Demo Board Schematic

U1

OR

SW

GND

5





4

100

1.5

MBR0520LT1



2

FB

3.0

R1B
332k
5V

3.5

4.0

C2

+

100µF

6.3V

2.5

2.0
INPUT VOLTAGE (V)

D1

R2

1.00M

3.3V

5V

231

JP1

R1A
604k

3.3V

4.5

DC194 G02

5.0

C4

0.1µF

DC194 F01

V

GND

OUT

2

DEMO MANUAL DC194

MICROPOWER BOOST REGULATOR

PARTS LIST

REFERENCE
DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE

C1 1 TPSB226M010R0700 22µF 10V 20% Tantalum Capacitor AVX [phone]
C2 1 TPSC107M006R0150 100µF 6.3V 20% Tantalum Capacitor AVX [phone]
C3 1 0805YG332KAT2 3300pF 16V Y5V 0805 Capacitor AVX [phone]
C4 1 08053G104KAT2 0.1µF 25V Y5V 0805 Capacitor AVX [phone]
C5 1 0805YG101KAT2 100pF 16V Y5V 0805 Capacitor AVX [phone]
D1 1 MBR0520LT1 20V 0.5A SOD123 Schottky Diode Motorola [phone]
L1 1 CD43-100MC 10µH CD43 Inductor Sumida [phone]
R1A 1 CR10-6043F-T 604k 1/10W 1% 0805 Resistor TAD [phone]
R1B 1 CR10-3323F-T 332k 1/10W 1% 0805 Resistor TAD [phone]
R2 1 CR10-1004F-T 1M 1/10W 1% 0805 Resistor TAD [phone]
R3 1 CR10-333J-T 33k 1/8W 5% 0805 Resistor TAD [phone]
R4 (Optional) 1 CR18-104J-T 100k 1/8W 5% 1206 Resistor TAD [phone]
R5 to R7 (Optional) 3 CR18-XXXJ-T XXX 1/8W 5% 1206 Resistor TAD [phone]
JP1 1 3801S-03-G1 3-Pin Header, 0.1" Center Comm [phone]

1 CCIJ230-G SHUNT FOR JP1 Comm [phone]

U1 1 LT1317CMS8, MSOP LTHA DC/DC Converter Version A LTC [phone]

LT1317BCMS8, MSOP LTHB DC/DC Converter Version B

QUICK START GUIDE

DC194 can regulate a 3.3V output from an input of 1.5V
to 3.6V; it can regulate a 5V output from an input of 1.5V
to 5.3V. Select the desired output voltage by moving
jumper JP1 to the appropriate position. Apply the DC
input voltage between the VIN and GND terminals of the
DC194. Do not apply more than 5.5V to the input of this
circuit.

With the input supply present, the LT1317/LT1317B will
regulate the output to 3.3V or 5V. Attach a suitable load
between V

and GND.

OUT

The LT1317/LT1317B can be placed in shutdown mode
by tying the SHDN terminal to the GND terminal. For
normal operation, the SHDN terminal can be left floating
or pulled high (above 1.4V and up to VIN).

Note that, as with any boost regulator, there is a direct DC
path between the input and output; a shorted output will
draw large currents, possibly damaging the DC194.

3

DEMO MANUAL DC194

MICROPOWER BOOST REGULATOR

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OPERATIO

INTRODUCTION

The LT1317 and LT1317B are 600kHz PWM step-up
DC/DC converters. With a wide input voltage range (1.5V
to 12V) and high switch voltage (30V), these parts are
suitable for a wide variety of switching regulator circuits.
DC194 demonstrates their application in a simple boost
regulator with an output of either 3.3V or 5V.

DC194 is available in two versions. Version A uses the
LT1317CMS8. At light loads, this part switches automati­cally into power-saving Burst Mode operation, resulting in
high efficiency over a broad range of load currents. Ver­sion B uses the LT1317BCMS8, which operates at a fixed
frequency, regardless of load, eliminating low frequency
ripple on the output at the expense of light load efficiency.
You can confirm which version of the board you have by
checking the code on the IC; the LT1317 is marked with the
code LTHA, whereas the LT1317B is marked with LTHB. In
the comments below, “LT1317” will refer to both parts. In
cases where their characteristics result in different behav­ior, the LT1317B will be mentioned explicitly.

This manual describes the operation of this demonstration
circuit, its performance and variations on the basic circuit.
For a thorough discussion of the LT1317 and its applica­tion, please consult the part’s data sheet.

Hookup and Initial Tests

Select the desired output voltage by moving jumper JP1.
The input can safely accept a voltage up to 5.5V. A good
starting point is to apply 2.5V between the VIN and GND
terminals of the DC194, using a bench-top supply with a
1A current limit. Because the SHDN pin of the LT1317 has
been left floating, the LT1317 will begin operating as soon
as VIN is above 1.5V.

A load can be applied between the V

and GND termi-

OUT

nals, using either a fixed resistor, a decade resistor box
(provided that it is rated for the power) or an active load.
A simple initial load might be a 1/2W 100Ω resistor.
Warning: Because the basic boost circuit contains a DC
path between the input and output (through inductor L1
and diode D1), the circuit is not protected against a
shorted output. It is recommended that preliminary test­ing of the circuit be performed using a current-limited
supply on the input.

With power applied to the DC194, the LT1317 should be
switching and regulating the output. Figure 3 shows some
of the circuit’s operating waveforms. The scope photos
show the output voltage, the current through inductor L1
and the voltage on the SW pin of the LT1317. The LT1317
is in Burst Mode operation in the first photo. The second
photo shows operation at a higher load current, where the
LT1317 is operating at a fixed frequency. LT1317B circuits
will operate in this mode at all load currents.

DC194 is a fairly simple low power switching regulator.
However, some precautions are necessary in order to test
the circuit safely. Proper hookup and accurate measure­ments are necessary for meaningful evaluation of effi­ciency and line and load regulation. Refer to Figure 2 for
proper connections.

I

OUT

A

V

V

OUT

BENCH

SUPPLY

1.5V TO 5.5V
1A

Figure 2. Recommended Hookup for Proper Evaluation
of Efficiency and Regulation (See Text)

A

C

BULK

+

I

IN

V

V

IN

4

V

OUT

GND

V

IN

DC194

DC194 F02

PERFORMANCE
Input Range and Power Capability

The LT1317 will operate from inputs above 1.5V. The
maximum allowable input voltage to this circuit is 5.5V,
which is based on the voltage ratings of the input and
output capacitors C1 and C2. The boost circuit will allow
the LT1317 to regulate the output only when the input
voltage is less than the desired output voltage plus one
diode drop. This means that the practical input range is

1.5V to 3.6V for a 3.3V output and 1.5V to 5.3V for a 5V
output.

The power capability of the DC194 is determined primarily
by the input voltage and the current limit of the LT1317’s
internal power switch and, to a lesser extent, by the value
of inductor L1. Therefore, the maximum load current that
this circuit can supply depends on the input voltage. A