DEMO MANUAL DC194
MICROPOWER BOOST REGULATOR
LT1317/LT1317B
Micropower, 600kHz
PWM DC/DC Converters
result in small, cost effective solutions. The micropower
LT1317 shifts automatically to low power Burst Mode
TM
operation at light loads, whereas the LT1317B operates at
a fixed frequency at all loads. Both parts feature a low-
battery 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.
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 con-
verters. Their high operating frequency and small package
PERFOR A CE SU
PARAMETER
Input Voltage (Note 1)
Maximum Load Current, Min
Shutdown Current, Typ
No Load Quiescent Current, Typ
Note 1:
This limit is based on the DC194 circuit. The LT1317 can operate
from high supply voltages.
TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO
LT1317 Efficiency
90
V
IN
= 3V
80
EFFICIENCY (%)
LT1317 Efficiency
90
V
IN
= 3.3V
80
70
V
IN
= 1.6V
V
IN
= 2.4V
EFFICIENCY (%)
V
IN
= 2.4V
70
V
IN
= 1.6V
60
60
50
LT1317
V
OUT
= 3.3V
40
0.3
1
10
100
LOAD CURRENT (mA)
1000
DC194 G04
50
LT1317
V
OUT
= 5V
40
0.3
1
10
100
LOAD CURRENT (mA)
1000
DC194 G03
DC194 BP
U
WW
U W
U
ARY
CONDITIONS
V
OUT
= 3.3V
V
OUT
= 5V
V
OUT
= 3.3V, V
IN
= 1.6V
V
OUT
= 3.3V, V
IN
= 2.4V
V
OUT
= 5V, V
IN
= 2V
V
OUT
= 5V, V
IN
= 3.3V
V
IN
= 2.5V, SHDN = 0V
U W
VALUE
1.5V to 3.6V
1.5V to 5.3V
175mA
320mA
140mA
290mA
25µA
125µA
4.8mA
V
OUT
= 3.3V, V
IN
= 2.4V, LT1317
V
OUT
= 3.3V, V
IN
= 2.4V, LT1317B
Board Photo
1
DEMO MANUAL DC194
MICROPOWER BOOST REGULATOR
TYPICAL PERFORMANCE CHARACTERISTICS
LT1317B Efficiency
90
LT1317B
V
OUT
= 3.3V
80
EFFICIENCY (%)
EFFICIENCY (%)
V
IN
= 3V
80
V
IN
= 2.4V
70
V
IN
= 1.6V
60
50
40
1
10
100
LOAD CURRENT (mA)
1000
DC194 G06
Load Current vs Input Voltage
600
V
OUT
= 3.3V
500
OUTPUT CURRENT (mA)
TYPICAL
400
MINIMUM
300
OUTPUT CURRENT (mA)
200
100
1.5
2.0
INPUT VOLTAGE (V)
DC194 G01
PACKAGE A D SCHE ATIC DIAGRA SM
TOP VIEW
V
C
FB
SHDN
GND
1
2
3
4
8
7
6
5
LBO
LBI
V
IN
SW
LT1317CMS8
LT1317BCMS8
L1
10µH
V
IN
R7
OPT
R6
OPT
R4
OPT
D1
MBR0520LT1
V
OUT
5
SW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
+
SHDN
LBI
LBO
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
C1
22µF
10V
3
U1
LT1317CMS8(A)
SHDN
LTHA
2
7
OR
LBI
FB
LT1317BCMS8(B)
8
LBO
LTHB
V
C
GND
4
1
R3
33k
C3
3300pF
R5
OPT
C5
100pF
Figure 1. Demo Board Schematic
2
W
W
U W
2.5
LT1317B Efficiency
90
LT1317B
V
OUT
= 5V
V
IN
= 3.3V
70
V
IN
= 2.4V
V
IN
= 1.6V
60
50
40
1
10
100
LOAD CURRENT (mA)
1000
DC194 G05
Load Current vs Input Voltage
600
V
OUT
= 5V
500
400
TYPICAL
300
MINIMUM
200
100
3.0
3.5
1.5
2.0
2.5 3.0 3.5
4.0
INPUT VOLTAGE (V)
4.5
5.0
DC194 G02
U
6
V
IN
R2
1.00M
C4
0.1µF
+
3.3V
5V
C2
100µF
6.3V
1
2
3
JP1
R1A
604k
3.3V
R1B
332k
5V
GND
DC194 F01
DEMO MANUAL DC194
MICROPOWER BOOST REGULATOR
PARTS LIST
REFERENCE
DESIGNATOR
C1
C2
C3
C4
C5
D1
L1
R1A
R1B
R2
R3
R4 (Optional)
R5 to R7 (Optional)
JP1
U1
QUANTITY
1
1
1
1
1
1
1
1
1
1
1
1
3
1
1
1
PART NUMBER
TPSB226M010R0700
TPSC107M006R0150
0805YG332KAT2
08053G104KAT2
0805YG101KAT2
MBR0520LT1
CD43-100MC
CR10-6043F-T
CR10-3323F-T
CR10-1004F-T
CR10-333J-T
CR18-104J-T
CR18-XXXJ-T
3801S-03-G1
CCIJ230-G
LT1317CMS8, MSOP
LT1317BCMS8, MSOP
DESCRIPTION
22µF 10V 20% Tantalum Capacitor
100µF 6.3V 20% Tantalum Capacitor
3300pF 16V Y5V 0805 Capacitor
0.1µF 25V Y5V 0805 Capacitor
100pF 16V Y5V 0805 Capacitor
20V 0.5A SOD123 Schottky Diode
10µH CD43 Inductor
604k 1/10W 1% 0805 Resistor
332k 1/10W 1% 0805 Resistor
1M 1/10W 1% 0805 Resistor
33k 1/8W 5% 0805 Resistor
100k 1/8W 5% 1206 Resistor
XXX 1/8W 5% 1206 Resistor
3-Pin Header, 0.1
"
Center
SHUNT FOR JP1
LTHA DC/DC Converter Version A
LTHB DC/DC Converter Version B
VENDOR
AVX
AVX
AVX
AVX
AVX
Motorola
Sumida
TAD
TAD
TAD
TAD
TAD
TAD
Comm
Comm
LTC
TELEPHONE
(207) 282-5111
(207) 282-5111
(843) 946-0362
(843) 946-0362
(843) 946-0362
(800) 441-2447
(847) 956-0666
(800) 508-1521
(800) 508-1521
(800) 508-1521
(800) 508-1521
(714) 255-9123
(714) 255-9123
(626) 301-4200
(626) 301-4200
(408) 432-1900
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 V
IN
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
OUT
and GND.
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 V
IN
).
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
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 automati-
cally into power-saving Burst Mode operation, resulting in
high efficiency over a broad range of load currents. Ver-
sion 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 behav-
ior, 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 applica-
tion, please consult the part’s data sheet.
Hookup and Initial Tests
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 measure-
ments are necessary for meaningful evaluation of effi-
ciency and line and load regulation. Refer to Figure 2 for
proper connections.
A
I
OUT
V
OUT
A
I
IN
Figure 2. Recommended Hookup for Proper Evaluation
of Efficiency and Regulation (See Text)
4
+
BENCH
SUPPLY
1.5V TO 5.5V
1A
U
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 V
IN
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 V
IN
is above 1.5V.
A load can be applied between the V
OUT
and GND termi-
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 test-
ing 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.
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
V
V
OUT
GND
DC194
C
BULK
V
V
IN
V
IN
DC194 F02
DEMO MANUAL DC194
MICROPOWER BOOST REGULATOR
OPERATIO
V
OUT
AC COUPLED
100mV/DIV
I
L1
200mA/DIV
V
SW
5V/DIV
V
OUT
AC COUPLED
100mV/DIV
I
L1
200mA/DIV
V
SW
5V/DIV
Figure 3. DC194’s Operating Waveforms. In the Upper Photo,
the LT1317 Is in Burst Mode, Delivering 50mA to the Load. In
the Lower Photo, the Load Curent Is 160mA and the LT1317 Is
Switching at 600kHz. V
IN
= 2.5V, V
OUT
= 3.3V
graph of maximum load appears in the Typical Perfor-
mance section of this manual. The lower curve shows the
guaranteed load capability based on the minimum current
limit specification in the LT1317 data sheet. The upper
curve shows the load capability of a typical DC194. As load
current is increased beyond this level, the output voltage
will sag as the LT1317 reaches its current limit. Again, be
aware that L1 and D1 provide a direct path between the
input and output and that this circuit does not limit the
output current. As an increasing load drags the output
voltage below the input, a larger current will flow, limited
only by the impedance of the power source, inductor L1
and diode D1.
Shutdown Mode
The SHDN pin of the LT1317 is tied directly to the SHDN
terminal of the DC194 and has been left floating. An
internal current source will pull up on this pin and the
U
LT1317 will run in this condition. The LT1317 will also
operate if this pin is pulled above 1.4V by an external
signal. The SHDN pin can be pulled as high as V
IN
+ 0.3V.
The LT1317 is placed in shutdown mode by pulling this pin
below 0.4V; you can do this by tying the SHDN terminal of
the DC194 to the GND terminal. The current consumption
of the LT1317 in shutdown mode is typically 25µA. How-
ever, the load can draw additional current through the
inductor and catch diode, raising the power consumption
in shutdown. The LT1317’s low-battery detector remains
active in shutdown. Applications of the low-battery detec-
tor are discussed below.
Efficiency
The efficiency of the DC194 is plotted in the Typical
Performance section of this manual. Efficiency measure-
ments should be made with care, as there is plenty of
opportunity for errors to creep in.
1µs/DIV
DC194 F03b
5µs/DIV
DC194 F03a
The efficiency is defined as the power delivered to the load
divided by the power drawn from the input supply. Nor-
mally, the average input voltage, input current, output
voltage and output current are measured under steady-
state conditions and the efficiency is calculated from these
values. Each should be measured with the highest accu-
racy and precision possible.
Figure 2 shows connections for the proper measurement
of efficiency and output regulation. The input and output
voltages are measured at the DC194 in order to avoid
including voltage drops across ammeters and terminal
connections. It is best to take all of these measurements
at one time. Be aware that most digital multimeters drop
significant voltage when they are used as ammeters, so
you must measure the input voltage while the ammeter is
in the circuit—the input voltage will be lower than the
voltage at the output of your bench-top supply. Another
difficulty occurs at low power when the LT1317 is in Burst
Mode operation. Here, the part will be drawing a few
hundred milliamperes while switching, but only a few
hundred microamperes average. An ammeter set to a
sensitive scale will have too much resistance to allow
these pulses of current to pass without large voltage
drops. The result is that the power delivered to the LT1317
is not equal to the average current times the average
5
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