1
LTC1517-3.3
Micropower, Regulated
3.3V Charge Pump in a
5-Pin SOT-23 Package
FEATURES
DESCRIPTIO
N
U
s
Ultralow Power: I
CC
= 6
A Typ
s
Short-Circuit/Thermal Protected
s
3.3V
4% Regulated Output
s
V
IN
Range: 2V to 4.4V
s
Output Current: 8mA (V
IN
2V)
15mA (V
IN
2.5V)
s
No Inductors
s
Ultrasmall Application Circuit (0.045in
2
)
s
700kHz Switching Frequency
s
Available in 5-Pin SOT-23
The LTC
1517-3.3 is a micropower charge pump DC/DC
converter that produces a regulated 3.3V output. The input
voltage range is 2V to 4.4V, allowing a single cell lithium
battery to produce a regulated 3.3V output over the entire life
of the battery. Extremely low operating current (typically 6
A
with no load) and low external parts count (one 0.1
F flying
capacitor and two small bypass capacitors at V
IN
and V
OUT
)
make the part ideally suited for small, light load battery-
powered applications. The total printed circuit board area of
the application circuit shown below is only 0.045in
2
.
The part operates as a Burst Mode
TM
switched-capacitor
voltage doubler to produce a regulated output. The part has
thermal shutdown capability and can survive a continuous
short circuit from V
OUT
to GND. The device is available in a
5-pin SOT-23 package.
s
Cellular Telephones
s
Battery-Operated Equipment
s
Local Power Supplies
s
Handheld Instruments
s
PCMCIA Supplies
APPLICATIO
N
S
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
N
U
3.3
F
1517-3.3 TA01
1
2
3
4
5
0.1
F
6.8
F
V
OUT
= 3.3V
4%
I
OUT
= 8mA (V
IN
2V)
I
OUT
= 15mA (V
IN
2.5V)
V
IN
2V TO 4.4V
V
IN
GND
LTC1517-3.3
V
OUT
C1
+
C1
OUTPUT CURRENT (mA)
0
OUTPUT VOLTAGE (V)
40
1517 G05
10
20
30
3.40
3.35
3.30
3.25
3.20
T
A
= 25
C
C1 = 0.1
F
C
OUT
= 6.8
F
V
IN
= 2V
V
IN
= 2.5V
Typical Output Voltage
vs Output Current
2
LTC1517-3.3
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
ORDER PART
NUMBER
Consult factory for Industrial and Military grade parts.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Operating Input Voltage
q
2.0
4.4
V
V
OUT
Output Voltage
2V
V
IN
4.4V, I
OUT
8mA
q
3.17
3.3
3.43
V
2.5V
V
IN
4.4V, I
OUT
15mA
q
3.17
3.3
3.43
V
I
CC
Input Supply Current
2V
V
IN
4.4V, I
OUT
= 0
q
6
15
A
V
OUT
Ripple
V
IN
= 2.5V, I
OUT
= 15mA, C
OUT
= 6.8
F
50
mV
P-P
f
OSC
Oscillator Frequency
700
kHz
t
ON
V
OUT
Turn-On Time
V
IN
= 2.5V
1
ms
I
SC
Output Short-Circuit Current
V
IN
= 3V
60
mA
V
IN
= 2V to 4.4V, C1 = 0.1
F, C
IN
= 3.3
F, C
OUT
= 6.8
F, T
MIN
to T
MAX
, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
C1
5
C1
+
1
2
3
V
IN
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC SOT-23
V
OUT
GND
4
(Note 1)
V
IN
to GND ................................................... 0.3V to 6V
V
OUT
to GND ................................................ 0.3V to 6V
V
OUT
Short-Circuit Duration ............................. Indefinite
Operating Temperature Range:
Commercial (Note 2) .............................. 0
C to 70
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec) .................. 300
C
S5 PART MARKING
LTEF
LTC1517CS5-3.3
T
JMAX
= 125
C,
JA
= 256
C/ W
The
q
denotes specifications that apply over the full operating
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: Commercial grade parts are designed to operate over the
temperature range of 40
C to 85
C but are neither tested nor guaranteed
beyond 0
C to 70
C.
3
LTC1517-3.3
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
INPUT VOLTAGE (V)
2.0
OUTPUT VOLTAGE (V)
4.0
1517 G01
2.5
3.0
3.5
4.5
3.40
3.35
3.30
3.25
3.20
I
OUT
= 8mA
C
OUT
= 6.8
F
T
A
= 70
C
T
A
= 0
C
T
A
= 25
C
Output Voltage vs Input Voltage
INPUT VOLTAGE (V)
2.0
EFFICIENCY (%)
4.0
1517 G02
2.5
3.0
3.5
4.5
100
80
60
40
20
I
OUT
= 8mA
T
A
= 25
C
Efficiency vs Input Voltage
INPUT VOLTAGE (V)
2.0
V
RIPPLE P-P
(mV)
4.0
1517 G03
2.5
3.0
3.5
4.5
200
150
100
50
0
I
OUT
= 8mA
C1 = 0.1
F
C
IN
= 3.3
F
T
A
= 25
C
C
OUT
= 3.3
F
C
OUT
= 6.8
F
C
OUT
= 10
F
Output Ripple vs Input Voltage
Load Transient Response
I
OUT
0mA to 10mA
5mA/DIV
V
OUT
AC COUPLED
50mV/DIV
V
IN
= 2.5V
500
s/DIV
C
OUT
= 6.8
F
1517 G06
No Load Input Current vs
Input Voltage
INPUT VOLTAGE (V)
2.0
INPUT CURRENT (
A)
4.0
1517 G04
2.5
3.0
3.5
4.5
10
8
6
4
2
I
OUT
= 0mA
T
A
= 70
C
T
A
= 0
C
T
A
= 25
C
TEMPERATURE (
C)
50
OUTPUT CURRENT (mA)
50
40
30
20
10
0
25
0
25
50
1517 G09
75
100
V
OUT
= 3.3V
C1 = 0.1
F
V
IN
= 2.7V
V
IN
= 2.5V
V
IN
= 2V
Typical Output Current
vs Temperature
INPUT VOLTAGE (V)
2.0
V
OUT
SHORT-CIRCUIT CURRENT (mA)
200
160
120
80
40
0
4.0
1517 G10
2.5
3.0
3.5
4.5
T
A
= 25
C
C1 = 0.1
F
V
OUT
Short-Circuit Current
vs Input Voltage
OUTPUT CURRENT (mA)
0.001
EFFICIENCY (%)
100
80
60
40
20
0
10
1517 TA02
0.01
0.1
1
100
T
A
= 25
C
C1 = 0.1
F
C
OUT
= 6.8
F
V
IN
= 2V
V
IN
= 2.5V
Typical Efficiency vs
Output Current
4
LTC1517-3.3
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SI PLIFIED
W
BLOCK DIAGRA
W
1517-3.3 BD
C1
0.1
F
V
IN
CHARGE PUMP
V
OUT
2.05M
1.25M
C
OUT
C
IN
C1
+
C1
700kHz
OSC
THERMAL
SHDN
1.25V
REF
+
V
IN
(Pin 1): Charge Pump Input Voltage. May be between
2V and 4.4V. V
IN
should be bypassed with a
3.3
F low
ESR capacitor as close as possible to the pin for best
performance.
GND (Pin 2): Ground. Should be tied to a ground plane for
best performance.
V
OUT
(Pin 3): Regulated Output Voltage. V
OUT
should be
bypassed with a
3.3
F low ESR capacitor as close as
possible to the pin for best performance.
PI
N
FU
N
CTIO
N
S
U
U
U
C1
+
(Pin 4): Charge Pump Flying Capacitor Positive
Terminal.
C1
(Pin 5): Charge Pump Flying Capacitor Negative
Terminal.
Oscillator Frequency vs
Input Voltage
INPUT VOLTAGE (V)
2.0
OSCILLATOR FREQUENCY (kHz)
4.0
1517 G07
2.5
3.0
3.5
4.5
900
800
700
600
500
T
A
= 25
C
Oscillator Frequency vs
Temperature
TEMPERATURE (
C)
50
OSCILLATOR FREQUENCY (kHz)
900
800
700
600
500
400
25
0
25
50
1517 G08
75
100
V
IN
= 2.5V
5
LTC1517-3.3
APPLICATIO
N
S I
N
FOR
M
ATIO
N
W
U
U
U
Output Ripple
Normal LTC1517-3.3 operation produces voltage ripple
on the V
OUT
pin. Output voltage ripple is required for the
parts to regulate. Low frequency ripple exists due to the
hysteresis in the sense comparator and propagation de-
lays in the charge pump enable/disable circuits. High
frequency ripple is also present mainly from the ESR
(equivalent series resistance) in the output capacitor.
Typical output ripple with V
IN
= 2.5V under maximum load
is 75mV peak-to-peak with a low ESR 3.3
F output capaci-
tor (minimum recommended C
OUT
). For applications
requiring V
IN
to exceed 3.3V or for applications requiring
less than 75mV of peak-to-peak ripple, a 6.8
F to 10
F
C
OUT
capacitor is recommended. Slight further decreases
in output ripple can be achieved by using C
OUT
capacitors
larger than 10
F.
Short-Circuit/Thermal Protection
During short-circuit conditions, the LTC1517-3.3 will draw
between 20mA and 150mA from V
IN
, causing a rise in
junction temperature. On-chip thermal shutdown circuitry
disables the charge pump once the junction temperature
exceeds approximately 160
C. The charge pump is
reenabled once the junction temperature drops to approxi-
mately 145
C. The LTC1517-3.3 will cycle in and out of
thermal shutdown indefinitely without latchup or damage
until the V
OUT
short is removed.
Operation
The LTC1517-3.3 uses a switched-capacitor charge pump
to boost V
IN
to a 3.3V
4% regulated output. The part
achieves regulation by sensing the output voltage through
an internal resistor divider and enabling the charge pump
when the divided output droops below the comparator's
lower trip point (set by V
REF
). When the charge pump is
enabled, a 2-phase nonoverlapping clock controls the
internal charge pump switches. Flying capacitor C1 is
charged to V
IN
on phase one of the clock. On phase two of
the clock, C1 is stacked in series with V
IN
and connected
to V
OUT
through an internal switch. This sequence of
charging and discharging the flying capacitor occurs at a
free running frequency of 700kHz (typ) and continues until
the divided output voltage reaches the upper trip point of
the comparator. Once the output is back in regulation, the
charge pump is disabled. This method of bursting the
charge pump on and off enables the LTC1517-3.3 to
achieve high efficiency at extremely low output loads.
Capacitor Selection
For best performance, it is recommended that low ESR
capacitors be used for both C
IN
and C
OUT
to reduce noise
and ripple. The C
IN
and C
OUT
capacitors should be either
ceramic or tantalum and should be 3.3
F or greater.
Ceramic capacitors will provide the smallest size for a
given capacitance. If the input source impedance is very
low (< 0.5
), C
IN
may not be needed. Ceramic capacitors
are recommended for the flying capacitor C1 with values
of 0.1
F or 0.22
F. Smaller value flying capacitors may be
used in low I
OUT
applications.
6
LTC1517-3.3
TYPICAL APPLICATIO
N
S
U
Low Noise Boosted 3.3V Supply
Generating 3.3V and a Negative Supply
3.3
F
1517 TA05
1
2
3
4
5
0.1
F
0.1
F
*
**
10k
V
OUT
= 3.3V
4%
I
OUT
= 5mA (2V
V
IN
4.4V)
I
OUT
= 10mA (2.5V
V
IN
4.4V)
V
OUT
= 0.8V TO 3V
I
OUT
= 0mA to 5mA
V
IN
2V TO 4.4V
V
IN
GND
LTC1517-3.3
V
OUT
C1
+
C1
21.5k
470
3.3
F
CENTRAL SEMICONDUCTOR CMPSH-35 DUAL SCHOTTKY
OPTIONAL CIRCUITRY FOR MAINTAINING V
OUT
WITH LOW
V
OUT
LOADS
Q1, Q2: 2N3904
*
**
3.3
F
Q2
Q1
A
50mV/DIV
AC COUPLED
V
IN
= 2.7V
I
OUT
= 5mA
10
s/DIV
1517 TA04b
B
V
OUT
2mV/DIV
AC COUPLED
3.3
F
1517 TA04a
1
2
3
4
5
0.1
F
3.3
F
1
F
3.3
F
470
470
V
OUT
= 3.3V
I
OUT
= 8mA
V
RIPPLE
= 2mV
P-P
V
IN
2.7V TO 4.4V
V
IN
GND
LTC1517-3.3
V
OUT
C1
+
C1
Q2
Q1, Q2: 2N3904
Q1
A
B
7
LTC1517-3.3
PACKAGE DESCRIPTIO
N
U
Dimensions in inches (millimeters) unless otherwise noted.
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
0.95
(0.037)
REF
1.50 1.75
(0.059 0.069)
0.10 0.60
(0.004 0.024)
REF
0.35 0.50
(0.014 0.020)
FIVE PLACES (NOTE 2)
S5 SOT-23 0797
2.80 3.00
(0.110 0.118)
(NOTE 3)
1.90
(0.074)
REF
0.90 1.45
(0.035 0.057)
0.90 1.30
(0.035 0.051)
0.00 0.15
(0.00 0.006)
0.09 0.20
(0.004 0.008)
(NOTE 2)
2.60 3.00
(0.102 0.118)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
8
LTC1517-3.3
15173f LT/TP 0998 4K PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1998
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
q
FAX: (408) 434-0507
q
www.linear-tech.com
TYPICAL APPLICATIO
N
U
3.3
F
75k
2-CELL
NiCd
1517-3.3 TA03
1
3
4
5
6
3
2
2
3
7
8
1.1M
3.9V
TRIP
2
1
1
4
5
0.1
F
LOGIC LOW = BACKUP MODE
LTC1517-3.3
LTC1540
LT1521-3.3
1
F
MAIN
SUPPLY
5V
BAT54
TRICKLE CHARGE
AND LTC1517-3.3
I
DD
1.5
F
V
OUT
= 3.3V,
I
OUT
= 300mA
(I
OUT
= 8mA IN
BACKUP MODE)
3.3
F
SILICONIX
Si2301DS
470k
+
Low Power Battery Backup Supply with Autoswitchover and No Reverse Current
PART NUMBER
DESCRIPTION
COMMENTS
LTC1514-X
Step-Up/Step-Down Switched-Capacitor DC/DC Converter with
3.3V or 5V Output up to 50mA
Low Battery Comparator
LTC1515
Step-Up/Step-Down Switched-Capacitor DC/DC Converter with POR
Fixed or Adjustable Output up to 50mA
LTC1516
Micropower Regulated 5V Charge Pump DC/DC Converter
20mA for V
IN
2V, 50mA for V
IN
3V
LTC1517-5
Micropower Regulated 5V Charge Pump in a 5-Pin SOT-23 Package
I
OUT
up to 20mA
LTC1522
Micropower Regulated 5V Charge Pump DC/DC Converter
Same as LTC1517-5 with Shutdown
RELATED PARTS
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