LTC1517-3.3 - Micropower, Regulated 3.3V Charge Pump in a 5-Pin SOT-23 Package

LTC1517-3.3
Micropower, Regulated
3.3V Charge Pump in a
5-Pin SOT-23 Package
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DESCRIPTION
FEATURES
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Ultralow Power: ICC = 6µA Typ
Short-Circuit/Thermal Protected
3.3V ±4% Regulated Output
VIN Range: 2V to 4.4V
Output Current: 8mA (VIN ≥ 2V)
15mA (VIN ≥ 2.5V)
No Inductors
Ultrasmall Application Circuit (0.045in2)
700kHz Switching Frequency
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 6µA
with no load) and low external parts count (one 0.1µF flying
capacitor and two small bypass capacitors at VIN and VOUT)
make the part ideally suited for small, light load batterypowered applications. The total printed circuit board area of
the application circuit shown below is only 0.045in2.
The part operates as a Burst ModeTM switched-capacitor
voltage doubler to produce a regulated output. The part has
thermal shutdown capability and can survive a continuous
short circuit from VOUT to GND. The device is available in a
5-pin SOT-23 package.
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APPLICATIONS
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Cellular Telephones
Battery-Operated Equipment
Local Power Supplies
Handheld Instruments
PCMCIA Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATION
Typical Output Voltage
vs Output Current
3.40
0.1µF
4
C1 +
LTC1517-3.3
VIN
2V TO 4.4V
3.3µF
VIN
GND
VOUT
1
2
3
6.8µF
VOUT = 3.3V ± 4%
IOUT = 8mA (VIN ≥ 2V)
IOUT = 15mA (VIN ≥ 2.5V)
OUTPUT VOLTAGE (V)
5
C1 –
TA = 25°C
C1 = 0.1µF
COUT = 6.8µF
3.35
3.30
VIN = 2V
VIN = 2.5V
3.25
1517-3.3 TA01
3.20
0
20
30
10
OUTPUT CURRENT (mA)
40
1517 G05
1
LTC1517-3.3
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
VIN to GND ...................................................– 0.3V to 6V
VOUT to GND ................................................– 0.3V to 6V
VOUT Short-Circuit Duration ............................. Indefinite
Operating Temperature Range:
Commercial ............................................ 0°C to 70°C
Extended ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
TOP VIEW
VIN
1
GND
2
VOUT
3
5
C1 –
4
C1 +
LTC1517CS5-3.3
LTC1517ES5-3.3
S5 PACKAGE
5-LEAD PLASTIC SOT-23
S5 PART MARKING
TJMAX = 125°C, θJA = 256°C/ W
LTEF
LTTE
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
VIN = 2V to 4.4V, C1 = 0.1µF, CIN = 3.3µF, COUT = 6.8µF, TMIN to TMAX, unless otherwise noted.
SYMBOL
PARAMETER
VIN
Operating Input Voltage
VOUT
Output Voltage
ICC
CONDITIONS
MIN
●
2.0
2V ≤ VIN ≤ 4.4V, IOUT ≤ 8mA
2.5V ≤ VIN ≤ 4.4V, IOUT ≤ 15mA
●
●
3.17
3.17
Input Supply Current
2V ≤ VIN ≤ 4.4V, IOUT = 0
●
VOUT Ripple
VIN = 2.5V, IOUT = 15mA, COUT = 6.8µF
TYP
MAX
UNITS
4.4
V
3.3
3.3
3.43
3.43
V
V
6
15
µA
50
mVP-P
fOSC
Oscillator Frequency
700
kHz
tON
VOUT Turn-On Time
VIN = 2.5V
1
ms
ISC
Output Short-Circuit Current
VIN = 3V
60
mA
The ● 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.
2
Note 2: Extended grade parts are 100% tested at TA = 25°C. Performance
at – 40°C and 85°C is assured by design, characterization and correlation
with statistical process controls.
LTC1517-3.3
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TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage vs Input Voltage
200
100
IOUT = 8mA
COUT = 6.8µF
IOUT = 8mA
C1 = 0.1µF
CIN = 3.3µF
TA = 25°C
IOUT = 8mA
TA = 25°C
3.35
150
TA = 70°C
3.30
TA = 0°C
TA = 25°C
VRIPPLE P-P (mV)
80
EFFICIENCY (%)
OUTPUT VOLTAGE (V)
Output Ripple vs Input Voltage
Efficiency vs Input Voltage
3.40
60
3.25
COUT = 3.3µF
100
COUT = 6.8µF
50
40
COUT = 10µF
3.20
2.0
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
20
2.0
4.5
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
1517 G01
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
Typical Efficiency vs
Output Current
10
4.5
1517 G03
1517 G02
No Load Input Current vs
Input Voltage
Load Transient Response
100
IOUT = 0mA
TA = 25°C
C1 = 0.1µF
COUT = 6.8µF
80
EFFICIENCY (%)
8
TA = 70°C
6
TA = 25°C
TA = 0°C
VIN = 2V
IOUT
0mA to 10mA
5mA/DIV
VIN = 2.5V
60
VOUT
AC COUPLED
50mV/DIV
40
4
20
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
VIN = 2.5V
COUT = 6.8µF
0
0.001
4.5
0.01
1
10
0.1
OUTPUT CURRENT (mA)
1517 G04
500µs/DIV
1517 G06
100
1517 TA02
Typical Output Current
vs Temperature
VOUT Short-Circuit Current
vs Input Voltage
200
50
VOUT = 3.3V
C1 = 0.1µF
VOUT SHORT-CIRCUIT CURRENT (mA)
2
2.0
40
OUTPUT CURRENT (mA)
INPUT CURRENT (µA)
0
2.0
4.5
VIN = 2.7V
30
VIN = 2.5V
20
VIN = 2V
10
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1517 G09
TA = 25°C
C1 = 0.1µF
160
120
80
40
0
2.0
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
4.5
1517 G10
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LTC1517-3.3
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TYPICAL PERFORMANCE CHARACTERISTICS
Oscillator Frequency vs
Input Voltage
Oscillator Frequency vs
Temperature
900
900
VIN = 2.5V
OSCILLATOR FREQUENCY (kHz)
OSCILLATOR FREQUENCY (kHz)
TA = 25°C
800
700
600
500
2.0
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
800
700
600
500
400
–50
4.5
–25
0
25
50
TEMPERATURE (°C)
75
100
1517 G08
1517 G07
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PIN FUNCTIONS
VIN (Pin 1): Charge Pump Input Voltage. May be between
2V and 4.4V. VIN should be bypassed with a ≥ 3.3µF low
ESR capacitor as close as possible to the pin for best
performance.
C1 + (Pin 4): Charge Pump Flying Capacitor Positive
Terminal.
C1 – (Pin 5): Charge Pump Flying Capacitor Negative
Terminal.
GND (Pin 2): Ground. Should be tied to a ground plane for
best performance.
VOUT (Pin 3): Regulated Output Voltage. VOUT should be
bypassed with a ≥ 3.3µF low ESR capacitor as close as
possible to the pin for best performance.
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SI PLIFIED BLOCK DIAGRA
C1
0.1µF
C1 –
VIN
C1 +
VOUT
CHARGE PUMP
CIN
2.05M
COUT
+
700kHz
OSC
–
THERMAL
SHDN
1.25M
1.25V
REF
1517-3.3 BD
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LTC1517-3.3
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APPLICATIONS INFORMATION
Operation
Output Ripple
The LTC1517-3.3 uses a switched-capacitor charge pump
to boost VIN 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 VREF). When the charge pump is
enabled, a 2-phase nonoverlapping clock controls the
internal charge pump switches. Flying capacitor C1 is
charged to VIN on phase one of the clock. On phase two of
the clock, C1 is stacked in series with VIN and connected
to VOUT 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.
Normal LTC1517-3.3 operation produces voltage ripple
on the VOUT 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 delays 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 VIN = 2.5V under maximum load
is 75mV peak-to-peak with a low ESR 3.3µF output capacitor (minimum recommended COUT). For applications
requiring VIN to exceed 3.3V or for applications requiring
less than 75mV of peak-to-peak ripple, a 6.8µF to 10µF
COUT capacitor is recommended. Slight further decreases
in output ripple can be achieved by using COUT capacitors
larger than 10µF.
Capacitor Selection
For best performance, it is recommended that low ESR
capacitors be used for both CIN and COUT to reduce noise
and ripple. The CIN and COUT capacitors should be either
ceramic or tantalum and should be 3.3µF or greater.
Ceramic capacitors will provide the smallest size for a
given capacitance. If the input source impedance is very
low (< 0.5Ω), CIN may not be needed. Ceramic capacitors
are recommended for the flying capacitor C1 with values
of 0.1µF or 0.22µF. Smaller value flying capacitors may be
used in low IOUT applications.
Short-Circuit/Thermal Protection
During short-circuit conditions, the LTC1517-3.3 will draw
between 20mA and 150mA from VIN, 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 approximately 145°C. The LTC1517-3.3 will cycle in and out of
thermal shutdown indefinitely without latchup or damage
until the VOUT short is removed.
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LTC1517-3.3
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TYPICAL APPLICATIONS
Low Noise Boosted 3.3V Supply
0.1µF
5
4
C1 –
C1 +
LTC1517-3.3
VIN
2.7V TO 4.4V
VIN
GND
VOUT
1
2
3
50mV/DIV
AC COUPLED
B
VOUT
2mV/DIV
AC COUPLED
A
3.3µF
470Ω
470Ω
A
3.3µF
Q1
B
3.3µF
Q2
VOUT = 3.3V
IOUT = 8mA
1µF
Q1, Q2: 2N3904
VIN = 2.7V
IOUT = 5mA
VRIPPLE = 2mVP-P
1517 TA04a
10µs/DIV
Generating 3.3V and a Negative Supply
0.1µF
5
4
C1 –
C1 +
LTC1517-3.3
VIN
2V TO 4.4V
VIN
GND
VOUT
1
2
3
3.3µF
3.3µF
470Ω
Q1
21.5k
Q2
10k
0.1µF
**
1517 TA05
3.3µF
*
*CENTRAL SEMICONDUCTOR CMPSH-35 DUAL SCHOTTKY
**OPTIONAL CIRCUITRY FOR MAINTAINING – VOUT WITH LOW
VOUT LOADS
Q1, Q2: 2N3904
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VOUT = 3.3V ± 4%
IOUT = 5mA (2V ≤ VIN ≤ 4.4V)
IOUT = 10mA (2.5V ≤ VIN ≤ 4.4V)
– VOUT = –0.8V TO – 3V
– IOUT = 0mA to 5mA
1517 TA04b
LTC1517-3.3
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PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
2.60 – 3.00
(0.102 – 0.118)
1.50 – 1.75
(0.059 – 0.069)
0.10 – 0.60
(0.004 – 0.024)
REF
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
1.90
(0.074)
REF
0.00 – 0.15
(0.00 – 0.006)
0.95
(0.037)
REF
0.90 – 1.45
(0.035 – 0.057)
0.35 – 0.50
0.90 – 1.30
(0.014 – 0.020)
(0.035 – 0.051)
FIVE PLACES (NOTE 2)
S5 SOT-23 0797
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LTC1517-3.3
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TYPICAL APPLICATION
Low Power Battery Backup Supply with Autoswitchover and No Reverse Current
MAIN
SUPPLY
5V
3
1µF
VOUT = 3.3V,
IOUT = 300mA
(IOUT = 8mA IN
BACKUP MODE)
1
LT1521-3.3
1.5µF
2
BAT54
0.1µF
75k
TRICKLE CHARGE
AND LTC1517-3.3
IDD
5
1
2-CELL
NiCd
4
LTC1517-3.3
3.3µF
3.3µF
2
7
1.1M
3.9VTRIP
470k
SILICONIX
Si2301DS
3
3
+
4
–
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LOGIC LOW = BACKUP MODE
5
6
1517-3.3 TA03
LTC1540
2
1
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1514-X
Step-Up/Step-Down Switched-Capacitor DC/DC Converter with
Low Battery Comparator
3.3V or 5V Output up to 50mA
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 VIN ≥ 2V, 50mA for VIN ≥ 3V
LTC1517-5
Micropower Regulated 5V Charge Pump in a 5-Pin SOT-23 Package
IOUT up to 20mA
LTC1522
Micropower Regulated 5V Charge Pump DC/DC Converter
Same as LTC1517-5 with Shutdown
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Linear Technology Corporation
15173fs, sn15173 LT/TP 0998 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1998