REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
ADP1109
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
Micropower Low Cost
Fixed 3.3 V, 5 V, 12 V and Adjustable
DC-to-DC Converter
FUNCTIONAL BLOCK DIAGRAMS
DRIVER
SW
V
IN
GND
COMPARATOR
A1
R1
SENSE
R2
250k
SHUTDOWN
+
ADP1109-3.3: R1 = 152k
ADP1109-5: R1 = 83k
ADP1109-12: R1 = 29k
Q1
120kHz
OSCILLATOR
1.25V
REFERENCE
Fixed Output
DRIVER
SW
V
IN
GND
COMPARATOR
A1
FB
SHUTDOWN
+
ADP1109
Q1
120kHz
OSCILLATOR
1.25V
REFERENCE
Adjustable Output
FEATURES
Operates at Supply Voltages 2 V to 12 V
Fixed 3.3 V, 5 V, 12 V and Adjustable Output
Minimum External Components Required
Ground Current: 320 A
Oscillator Frequency: 120 kHz
Logic Shutdown
8-Lead DIP and SO-8 Packages
APPLICATIONS
Cellular Telephones
Single-Cell to 5 V Converters
Laptop and Palmtop Computers
Pagers
Cameras
Battery Backup Supplies
Portable Instruments
Laser Diode Drivers
Hand-Held Inventory Computers
GENERAL DESCRIPTION
The ADP1109 is a versatile step-up switching regulator. The
device requires only minimal external components to operate as
a complete switching regulator.
The ADP1109-5 can deliver 100 mA at 5 V from a 3 V input
and the ADP1109-12 can deliver 60 mA at 12 V from a 5 V
input. The device also features a logic controlled shutdown
capability that, when a logic low is applied, will shut down the
oscillator.
The 120 kHz operating frequency allows for the use of small
surface mount components. The gated oscillator capability
eliminates the need for frequency compensation.
TYPICAL APPLICATION
SW
GND
ADP1109-12
+
D1
C1
22 F
16V
SENSE
L1
33 H
V
IN
5V
V
IN
SHUTDOWN
SHUTDOWN/PROGRAM
V
OUT
12V
60mA
Flash Memory VPP Generator
2
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ADP1109SPECIFICATIONS
Parameter
Conditions
Symbol
Min
Typ
Max
Units
QUIESCENT CURRENT
Switch Off
I
Q
450
590
µ
A
INPUT VOLTAGE
V
IN
2
9
V
COMPARATOR TRIP POINT
VOLTAGE
1.20
1.25
1.30
V
COMPARATOR HYSTERESIS
ADP1109
8
14
mV
OUTPUT VOLTAGE
ADP1109-3.3
2 V
V
IN
3 V
V
OUT
3.13
3.30
3.46
V
ADP1109-5
3 V
V
IN
5 V
4.75
5.00
5.25
V
ADP1109-12
3 V
V
IN
12 V
11.45
12.00
12.55
V
OUTPUT VOLTAGE RIPPLE
ADP1109-3.3
16
40
mV
ADP1109-5
20
50
mV
ADP1109-12
40
110
mV
OSCILLATOR FREQUENCY
T
A
= +25
°
C
f
OSC
100
120
140
kHz
90
155
kHz
DUTY CYCLE
Full Load
DC
40
50
70
%
SWITCH-ON TIME
T
A
= +25
°
C
t
ON
3.1
4.2
5.9
µ
s
3.0
6.5
µ
s
SWITCH SATURATION VOLTAGE
I
SW
= 500 mA
V
CESAT
ADP1109-3.3
V
IN
= 3 V
0.4
0.8
V
ADP1109-5
V
IN
= 3 V
0.4
0.8
V
ADP1109-12
V
IN
= 5 V
0.4
0.8
V
SWITCH LEAKAGE CURRENT
V
SW
= 12 V, T
A
= +25
°
C
1
10
µ
A
SHUTDOWN PIN HIGH
V
IH
2.0
V
SHUTDOWN PIN LOW
V
IL
0.8
V
SHUTDOWN PIN INPUT CURRENT
V
SHUTDOWN
= 2 V
I
IH
10
µ
A
SHUTDOWN PIN INPUT CURRENT
V
SHUTDOWN
= 0.8 V
I
IL
20
µ
A
NOTES
All limits at temperature extremes are guaranteed via correlation using standard quality control methods.
Specifications subject to change without notice.
(0 C
T
A
+70 C, V
IN
= 3 V unless otherwise noted)
SW
GND
ADP1109-5
+
1N5818
22 F
16V
SENSE
L1
15 H
L1 = CTX15-1
V
IN
= 2V
V
IN
300mA
at 3V INPUT
50mA
at 2V INPUT
+5V
Figure 1. 2 V to 5 V Converter
SW
GND
ADP1109-12
+
1N5818
10 F
20V
SENSE
L1
15 H
L1 = CTX15-1
V
IN
= 2V
V
IN
40mA
at 3V INPUT
10mA
at 2V INPUT
+12V
Figure 2. 2 V to 12 V Converter
SW
GND
ADP1109-12
+
1N5818
22 F
16V
SENSE
L1
15 H
L1 = CTX15-1
V
IN
= 2V
V
IN
300mA
at 3V INPUT
50mA
at 2V INPUT
+5V
SHUTDOWN
SHUTDOWN
Figure 3. 2 V to 5 V Converter
With Shutdown
ADP1109
3
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PIN FUNCTION DESCRIPTIONS
Pin
Mnemonic
Function
1
V
IN
Input Supply Voltage.
2, 5, 6
NC
No Connection.
3
SW
Collector Node of Power Transistor.
4
GND
Ground.
7
SHUTDOWN When logic low is applied to this pin,
oscillator is shut down.
8
FB(SENSE)
On the ADP1109A (Adjustable), this
pin goes directly to the comparator
input. On the ADP1109-3.3,
ADP1109-5 and ADP1109-12, this
pin is connected through the internal
resistor that sets the output voltage.
ORDERING GUIDE
Output
Package
Package
Model
Voltage
Description
Options
ADP1109AN
ADJ
Plastic DIP
N-8
ADP1109AR
ADJ
Small Outline IC
SO-8
ADP1109AN-3.3
3.3 V
Plastic DIP
N-8
ADP1109AR-3.3
3.3 V
Small Outline IC
SO-8
ADP1109AN-5
5 V
Plastic DIP
N-8
ADP1109AR-5
5 V
Small Outline IC
SO-8
ADP1109AN-12
12 V
Plastic DIP
N-8
ADP1109AR-12
12 V
Small Outline IC
SO-8
PIN CONFIGURATIONS
8-Lead Plastic DIP
(N-8)
TOP VIEW
(Not to Scale)
8
7
6
5
1
2
3
4
NC = NO CONNECT
*FIXED VERSIONS
V
IN
NC
SW
FB(SENSE)*
SHUTDOWN
NC
NC
GND
ADP1109A
8-Lead SOIC
(SO-8)
TOP VIEW
(Not to Scale)
8
7
6
5
1
2
3
4
NC = NO CONNECT
*FIXED VERSIONS
V
IN
NC
SW
GND
FB(SENSE)*
SHUTDOWN
NC
NC
ADP1109A
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADP1109 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage, V
OUT
. . . . . . . . . . . . . . . . . . . . 0.4 V to 20 V
SW Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . 0.4 V to 50 V
Shutdown Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 V
Switch Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 A
Maximum Power Dissipation . . . . . . . . . . . . . . . . . . 300 mW
Operating Temperature Range . . . . . . . . . . . . 0
°
C to +70
°
C
Storage Temperature Range . . . . . . . . . . . . 65
°
C to +150
°
C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . +300
°
C
*This is a stress rating only; operation beyond these limits can cause the device to
be permanently damaged.
ADP1109
4
REV. 0
INPUT VOLTAGE V
123.5
118.5
2
20
4
OSCILLATOR FREQUENCY kHz
6
8
10
12
14
16
18
123.0
121.0
120.0
119.5
119.0
122.5
122.0
120.5
121.5
Figure 4. Oscillator Frequency vs.
Input Voltage
TEMPERATURE C
150
40
OSCILLATOR FREQUENCY kHz
140
100
130
120
90
110
0
25
70
85
Figure 7. Oscillator Frequency vs.
Temperature
TEMPERATURE C
0.37
40
V
CE(SAT)
V
0.36
0.32
0.35
0.34
0.31
0.33
0
25
70
85
0.38
0.39
Figure 10. Switch Saturation Voltage
vs. Temperature
SWITCH CURRENT A
1.2
0.1
1
0.2
V
CESAT
V
0.3
0.4 0.5
0.6 0.7
0.8
0.9
1.0
0.2
0.8
0.6
0
0.4
Figure 5. Switch Saturation Voltage
vs. Switch Current
TEMPERATURE C
40
SWITCH-ON TIME
s
0
25
70
85
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
Figure 8. Switch-On Time vs.
Temperature
TEMPERATURE C
40
QUIESCENT CURRENT
A
100
400
300
0
200
0
25
70
85
600
500
Figure 11. Quiescent Current vs.
Temperature
INPUT VOLTAGE V
600
2
20
4
QUIESCENT CURRENT
A
6
8
10
12
14
16
18
500
100
400
300
0
200
Figure 6. Quiescent Current vs.
Input Voltage
TEMPERATURE C
54
40
DUTY CYCLE %
52
44
50
48
42
46
0
25
70
85
56
58
Figure 9. Duty Cycle vs. Temperature
Typical Performance Characteristics
ADP1109
5
REV. 0
APPLICATION INFORMATION
THEORY OF OPERATION
The ADP1109 is a flexible, low power switch-mode power sup-
ply (SMPS) controller for step-up dc/dc converter applications.
This device uses a gated-oscillator technique to provide very
high performance with low quiescent current. For example,
more than 2 W of output power can be generated from a +5 V
source, while quiescent current is only 450
µ
A.
A functional block diagram of the ADP1109 is shown on page 1.
The internal 1.25 V reference is connected to one input of the
comparator, while the other input is externally connected (via
the FB pin) to a feedback network connected to the regulated
output. When the voltage at the FB pin falls below 1.25 V, the
120 kHz oscillator turns on. A driver amplifier provides base
drive to the internal power switch, and the switching action
raises the output voltage. When the voltage at the FB pin ex-
ceeds 1.25 V, the oscillator is shut off. While the oscillator is off,
the ADP1109 quiescent current is only 450
µ
A. The comparator
includes a small amount of hysteresis, which ensures loop stabil-
ity without requiring external components for frequency com-
pensation.
A shutdown feature permits the oscillator to be shut off. Hold-
ing
SHUTDOWN low will disable the oscillator, and the
ADP1109's quiescent current will remain 450
µ
A.
The output voltage of the ADP1109 is set with two external
resistors. Three fixed-voltage models are also available: the
ADP1109-3.3 (+3.3 V), ADP1109-5 (+5 V) and ADP1109-12
(+12 V). The fixed-voltage models are identical to the ADP1109,
except that laser-trimmed voltage-setting resistors are included on
the chip. On the fixed-voltage models of the ADP1109, simply
connect the SENSE pin (Pin 8) directly to the output voltage.
COMPONENT SELECTION
General Notes on Inductor Selection
When the ADP1109 internal power switch turns on, current
begins to flow in the inductor. Energy is stored in the inductor
core while the switch is on, and this stored energy is then trans-
ferred to the load when the switch turns off.
To specify an inductor for the ADP1109, the proper values of
inductance, saturation current and dc resistance must be deter-
mined. This process is not difficult, and specific equations are
provided in this data sheet. In general terms, however, the induc-
tance value must be low enough to store the required amount of
energy (when both input voltage and switch ON time are at a
minimum), but high enough that the inductor will not saturate
when both V
IN
and switch ON time are at their maximum val-
ues. The inductor must also store enough energy to supply the
load, without saturating. Finally, the dc resistance of the induc-
tor should be low, so that excessive power will not be wasted by
heating the windings. For most ADP1109 applications, an in-
ductor of 10
µ
H to 47
µ
H, with a saturation current rating of
300 mA to 1 A and dc resistance <0.4
is suitable. Ferrite core
inductors that meet these specifications are available in small,
surface-mount packages. Air-core inductors, as well as RF chokes,
are unsuitable because of their low peak current ratings.
The ADP1109 is designed for applications where the input
voltage is fairly stable, such as generating +12 V from a +5 V
logic supply. The ADP1109 does not have an internal switch
current limiting circuit, so the inductor may saturate if the input
voltage is too high. The ADP1111 or ADP3000 should be
considered for battery powered and similar applications where
the input voltage varies.
To minimize Electro-Magnetic Interference (EMI), a toroid or
pot core type inductor is recommended. Rod core inductors are
a lower cost alternative if EMI is not a problem.
Calculating the Inductor Value
Selecting the proper inductor value is a simple, two-step process:
1. Define the operating parameters: minimum input voltage,
maximum input voltage, output voltage and output current.
2. Calculate the inductor value, using the equations in the fol-
lowing section.
Inductor Selection
In a step-up, or boost, converter (Figure 1), the inductor must
store enough power to make up the difference between the input
voltage and the output voltage. The inductor power is calculated
from the equation:
P
L
=
V
OUT
+
V
D
-
V
IN MIN
(
)
(
)
×
I
OUT
( )
(1)
where V
D
is the diode forward voltage ( 0.5 V for a 1N5818
Schottky). Energy is stored in the inductor only while the
ADP1109 switch is ON, so the energy stored in the inductor on
each switching cycle must be must be equal to or greater than:
P
L
f
OSC
(2)
in order for the ADP1109 to regulate the output voltage. When the
internal power switch turns ON, current flow in the inductor
increases at the rate of:
I
L
t
( )
=
V
IN
R'
1
-
e
-
R
'
t
L
(3)
where L is in Henrys and R' is the sum of the switch equivalent
resistance (typically 0.8
at +25
°
C) and the dc resistance of
the inductor. In most applications, the voltage drop across the
switch is small compared to V
IN
so a simpler equation can be
used:
I
L
t
( )
=
V
IN
L
t
(4)
Replacing t in the above equation with the ON time of the
ADP1109 (5.5
µ
s, typical) will define the peak current for a
given inductor value and input voltage. At this point, the induc-
tor energy can be calculated as follows:
E
L
=
1
2
L
×
I
2
peak
(5)
ADP1109
6
REV. 0
As previously mentioned, E
L
must be greater than P
L
/f
OSC
so
that the ADP1109 can deliver the necessary power to the load.
For best efficiency, peak current should be limited to 1 A or
less. Higher switch currents will reduce efficiency because of
increased saturation voltage in the switch. High peak current
also increases output ripple. As a general rule, keep peak current
as low as possible to minimize losses in the switch, inductor and
diode.
In practice, the inductor value is easily selected using the equa-
tions above. For example, consider a supply that will generate
12 V at 120 mA from a +5 V source. The inductor power re-
quired is, from Equation 1:
P
L
= (12 V + 0.5 V 5 V)
×
(120 mA) = 900 mW
(6)
On each switching cycle, the inductor must supply:
P
L
f
OSC
=
900 mW
120 kHz
=
7.5
µ
J
(7)
The required inductor power is fairly low in this example, so
the peak current can also be low. Assuming a peak current of
600 mA as a starting point, Equation 4 can be rearranged to
recommend an inductor value:
L
=
V
IN
I
L MAX
(
)
t
=
5 V
600 mA
5.5
µ
s
=
45.8
µ
H
(8)
Substituting a standard inductor value of 33
µ
H, with 0.2
dc
resistance, will produce a peak switch current of:
I
PEAK
=
5 V
1.0
1
-
e
1.0
×
5.5
µ
s
33
µ
H
=
768 mA
(9)
Once the peak current is known, the inductor energy can be
calculated from Equation 5:
E
L
=
1
2
33
µ
H
(
)
×
768 mA
(
)
2
=
9.7
µ
J
(10)
The inductor energy of 9.7
µ
J is greater than the P
L
/f
OSC
re-
quirement of 7.5
µ
J, so the 33
µ
H inductor will work in this
application. By substituting other inductor values into the same
equations, the optimum inductor value can be selected. When
selecting an inductor, the peak current must not exceed the
maximum switch current of 1.2 A. If the calculated peak current
is greater than 1.2 A, either the input voltage must be increased
or the load current decreased.
Output Voltage Selection
The output voltage is fed back to the ADP1109 via resistors R1
and R2 (Figure 5). When the voltage at the comparator's invert-
ing input falls below 1.25 V, the oscillator turns "on" and the
output voltage begins to rise. The output voltage is therefore set
by the formula:
V
OUT
=
1.25 V
×
1
+
R2
R1
(11)
Resistors R1 and R2 are provided internally on fixed-voltage
versions of the ADP1109. In this case, a complete dc-dc con-
verter requires only four external components.
Capacitor Selection
For optimum performance, the ADP1109's output capacitor
must be carefully selected. Choosing an inappropriate capacitor
can result in low efficiency and/or high output ripple.
Ordinary aluminum electrolytic capacitors are inexpensive, but
often have poor Equivalent Series Resistance (ESR) and Equiva-
lent Series Inductance (ESL). Low ESR aluminum capacitors,
specifically designed for switch mode converter applications, are
also available, and these are a better choice than general purpose
devices. Even better performance can be achieved with tantalum
capacitors, although their cost is higher. Very low values of ESR
can be achieved by using OS-CON capacitors (Sanyo Corpora-
tion, San Diego, CA). These devices are fairly small, available
with tape-and-reel packaging, and have very low ESR.
Diode Selection
In specifying a diode, consideration must be given to speed,
forward voltage drop and reverse leakage current. When the
ADP1109 switch turns off, the diode must turn on rapidly if
high efficiency is to be maintained. Schottky rectifiers, as well as
fast signal diodes such as the 1N4148, are appropriate. The
forward voltage of the diode represents power that is not
delivered to the load, so V
F
must also be minimized. Again,
Schottky diodes are recommended. Leakage current is especially
important in low current applications, where the leakage can be
a significant percentage of the total quiescent current.
For most circuits, the 1N5818 is a suitable companion to the
ADP1109. This diode has a V
F
of 0.5 V at 1 A, 4
µ
A to 10
µ
A
leakage, and fast turn-on and turn-off times. A surface mount
version, the MBRS130T3, is also available.
For switch currents of 100 mA or less, a Schottky diode such as
the BAT85 provides a V
F
of 0.8 V at 100 mA and leakage less
than 1
µ
A. A similar device, the BAT54, is available in an
SOT-23 package. Even lower leakage, in the 1 nA to 5 nA range,
can be obtained with a 1N4148 signal diode.
General purpose rectifiers, such as the 1N4001, are not suitable
for ADP1109 circuits. These devices, which have turn-on times
of 10
µ
s or more, are far too slow for switching power supply
applications. Using such a diode "just to get started" will result
in wasted time and effort. Even if an ADP1109 circuit appears
to function with a 1N4001, the resulting performance will not
be indicative of the circuit performance when the correct diode
is used.
ADP1109
7
REV. 0
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic DIP
(N-8)
8
1
4
5
0.430 (10.92)
0.348 (8.84)
0.280 (7.11)
0.240 (6.10)
PIN 1
SEATING
PLANE
0.022 (0.558)
0.014 (0.356)
0.060 (1.52)
0.015 (0.38)
0.210 (5.33)
MAX
0.130
(3.30)
MIN
0.070 (1.77)
0.045 (1.15)
0.100
(2.54)
BSC
0.160 (4.06)
0.115 (2.93)
0.325 (8.25)
0.300 (7.62)
0.015 (0.381)
0.008 (0.204)
0.195 (4.95)
0.115 (2.93)
8-Lead SOIC
(SO-8)
0.1968 (5.00)
0.1890 (4.80)
8
5
4
1
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.1574 (4.00)
0.1497 (3.80)
0.0688 (1.75)
0.0532 (1.35)
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.0500
(1.27)
BSC
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
°
0
°
0.0196 (0.50)
0.0099 (0.25)
x 45
°
8
C325181/98
PRINTED IN U.S.A.
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