LTC1516 - Micropower, Regulated 5V Charge Pump DC/DC Converter

LTC1516
Micropower, Regulated
5V Charge Pump
DC/DC Converter
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DESCRIPTION
FEATURES
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Ultralow Power: Typical Operating ICC = 12µA
Short Circuit/Thermal Protection
Regulated 5V ±4% Output
2V to 5V Input Range
No Inductors
ICC in Shutdown: < 1µA
Output Current: 20mA (VIN > 2V)
50mA (VIN > 3V)
Shutdown Disconnects Load from VIN
Internal Oscillator: 600kHz
Compact Application Circuit (0.1 in2)
8-Pin SO Package
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APPLICATIONS
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2-Cell to 5V Conversion
Li-Ion Battery Backup Supplies
Local 3V to 5V Conversion
5V Flash Memory Programmer
Smart Card Readers
The LTC1516 operates as either a doubler or a tripler
depending on VIN and output load conditions to improve
overall efficiency. The part has thermal shutdown and can
survive a continuous short from VOUT to GND. In shutdown the load is disconnected from VIN.
The LTC1516 is available in an 8-pin SO package in both
commercial and industrial temperature grades.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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The LTC®1516 is a micropower charge pump DC/DC
converter that produces a regulated 5V output from a 2V
to 5V supply. Extremely low supply current (12µA typical
with no load, < 1µA in shutdown) and low external parts
count (two 0.22µF flying capacitors and two 10µF capacitors at VIN and VOUT) make the LTC1516 ideally suited for
small, light load battery-powered applications. Typical
efficiency (VIN = 3V) exceeds 70% with load currents
between 50µA and 50mA. Modulating the SHDN pin keeps
the typical efficiency above 70% with load currents all the
way down to 10µA.
TYPICAL APPLICATION
Efficiency vs Output Current
0.22µF
90
VIN = 3V
1
8
C1–
C1+
2
+
10µF
3
+
10µF 4
VIN
SHDN
LTC1516
VOUT
GND
C2+
C2 –
7
ON/OFF
6
5
EFFICIENCY (%)
80
VIN = 2V TO 5V
70
LOW IQ MODE
(SEE FIGURE 3)
SHDN = 0V
60
0.22µF
VOUT = 5V ±4%
IOUT = 0mA TO 20mA, VIN ≥ 2V
IOUT = 0mA TO 50mA, VIN ≥ 3V
50
0.01
0.1
1
10
OUTPUT CURRENT (mA)
100
1516 • F01
1516 • TA01
Figure 1. Regulated 5V Output from a 2V to 5V Input
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LTC1516
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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
SHDN to GND ..............................................– 0.3V to 6V
VOUT Short-Circuit Duration ............................. Indefinite
Operating Temperature Range
Commercial ............................................. 0°C to 70°C
Industrial ............................................ – 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
C1+ 1
8 C1–
VIN 2
7 SHDN
VOUT 3
6 GND
C2+ 4
5 C2–
LTC1516CS8
LTC1516IS8
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
1516
1516I
TJMAX = 125°C, θJA = 150°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
VIN = 2V to 5V, C1 = C2 = 0.22µF, CIN = COUT = 10µF, TMIN to TMAX unless otherwise specified (Note 3).
SYMBOL PARAMETER
VIN
Input Voltage
VOUT
Output Voltage
ICC
fOSC
VIH
VIL
IIH
IIL
tON
Supply Current
Output Ripple
Efficiency
Switching Frequency
SHDN Input Threshold
CONDITIONS
●
2V ≤ VIN ≤ 5V, IOUT ≤ 20mA
3V ≤ VIN ≤ 3.6V, IOUT ≤ 50mA
3.6V ≤ VIN ≤ 5V, IOUT ≤ 50mA, TA = 25°C (Note 2)
2V ≤ VIN ≤ 5V, IOUT = 0mA, SHDN = 0V
2V ≤ VIN ≤ 5V, IOUT = 0mA, SHDN = VIN
Full Load
VIN = 3V, IOUT = 20mA
Full Load
TYP
12
0.005
100
82
600
●
●
●
VOUT Turn-On Time
VSHDN = VIN
VSHDN = 0V
VIN = 3V, IOUT = 0mA (Note 3)
●
●
MAX
5
5.2
5.2
5.2
20
1
(0.7)(VIN)
0.4
1
1
●
SHDN Input Current
The ● denotes specifications which 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
●
●
MIN
2
4.8
4.8
4.8
–1
–1
500
UNITS
V
V
V
V
µA
µA
mV
%
kHz
V
V
µA
µA
µs
Note 2: At input voltages > 3.6V and ambient temperatures >70°C,
continuous power dissipation must be derated to maintain junction
temperatures below 125°C. Derate 6mW/°C above 70°C in SO-8.
Note 3: The LTC1516 is tested with the capacitors shown in Figure 1.
LTC1516
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TYPICAL PERFORMANCE CHARACTERISTICS
120
MAXIMUM OUTPUT CURRENT (mA)
EFFICIENCY (%)
80
70
60
20
COUT = 10µF
TA = 25°C
IOUT = 10mA
100
C1 = C2
= 0.22µF
SUPPLY CURRENT (µA)
90
C1 = C2
= 0.1µF
80
60
C1 = C2
= 0.047µF
40
C1 = C2
= 0.022µF
20
C1 = C2 = 0.01µF
50
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
4.5
5.0
2
3
4
INPUT VOLTAGE (V)
1516 • G01
15
10
5
0
2.0
2
5
3
4
INPUT VOLTAGE (V)
Output Voltage vs Input Voltage
5
1516 • G03
1516 • G02
Output Voltage vs Output Current
Load Transient Response, VIN = 3V
5.10
5.10
VIN = 3V
IOUT = 20mA
5.05
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
No Load Supply Current vs
Input Voltage
Output Current vs Input Voltage
Efficiency vs Input Voltage
5.00
4.95
IOUT ,
0mA TO 25mA,
10mA/DIV
5.05
5.00
VOUT,
AC COUPLED,
100mV/DIV
4.95
1516 • G04
4.90
4.90
1
2
3
4
INPUT VOLTAGE (V)
5
6
0.01
0.1
1
10
OUTPUT CURRENT (mA)
1516 • G04
100
1516 • G05
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PIN FUNCTIONS
C1+ (Pin 1): Flying Capacitor 1, Positive Terminal.
GND (Pin 6): Ground.
VIN (Pin 2): Input Supply Voltage.
SHDN (Pin 7): Active High CMOS Logic-Level Shutdown
Input.
VOUT (Pin 3): 5V Output Voltage (VOUT = 0V in Shutdown).
C2+ (Pin 4): Flying Capacitor 2, Positive Terminal.
C1 – (Pin 8): Flying Capacitor 1, Negative Terminal.
C2 – (Pin 5): Flying Capacitor 2, Negative Terminal.
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LTC1516
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BLOCK DIAGRAM
VIN
10µF
SHDN
+
S2A
VOUT
+
S1A
C2 +
10µF
0.22µF
S2B
COMP1
C2 –
S1B
CLOCK 1
COMP2
CONTROL
LOGIC
S1C
C1 +
0.22µF
CLOCK 2
S2C
C1 –
COMP3
VOS
S1D
S3
VREF
CHARGE PUMP
CHARGE PUMP SHOWN IN TRIPLER MODE, DISCHARGE CYCLE
LTC1516 • BD
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APPLICATIONS INFORMATION
Operation
The LTC1516 uses a switched capacitor charge pump to
boost VIN from 2V to 5V to a regulated 5V ±4% output
voltage. Regulation is achieved by sensing the output
voltage through an internal resistor divider and enabling
the charge pump when the output voltage droops below
the lower trip point of COMP2. When the charge pump is
enabled, a 2-phase, nonoverlapping clock controls the
charge pump switches. Clock 1 closes the S1 switches
which enable the flying capacitors, C1 and C2, to charge
up to the VIN voltage. Clock 2 closes the S2 switches which
stack C1 and C2 in series with VIN and connect the top
plate of C2 to the output capacitor at VOUT. This sequence
of charging and discharging continues at a free-running
frequency of 600kHz (typ) until the output has risen to the
upper trip point of COMP2 and the charge pump is
disabled. When the charge pump is disabled, the LTC1516
draws only 8µA (typ) from VIN which provides high
efficiency at low load conditions.
To achieve the highest efficiency over the entire VIN range,
the LTC1516 operates as either a doubler or a tripler
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depending on VIN and output load conditions. COMP1 and
COMP2 determine whether the charge pump is in doubler
mode or tripler mode. COMP1 forces the part into tripler
mode if VIN is < 2.55V, regardless of output load. When VIN
is > 2.55V, the part will be in doubler mode using only C2
as a flying capacitor. In doubler mode, if the output droops
by 50mV under heavy loads, COMP3 will force the charge
pump into tripler mode until VOUT climbs above the upper
trip point of COMP3. Under these VIN and load conditions,
the nominal VOUT will be approximately 50mV lower than
the no load nominal VOUT. This method of sensing VIN and
output load results in efficiency greater than 80% with VIN
between 2.5V and 3V.
In shutdown mode, all circuitry is turned off and the part
draws only leakage current (< 1µA) from the VIN supply.
VOUT is also disconnected from VIN. The SHDN pin is a
CMOS input with a threshold of approximately VIN/2;
however, the SHDN pin can be driven by logic levels that
exceed the VIN voltage. The part enters shutdown mode
when a logic high is applied to the SHDN pin. The SHDN pin
cannot float; it must be driven with a logic high or low.
LTC1516
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APPLICATIONS INFORMATION
Short-Circuit/Thermal Protection
During short-circuit conditions, the LTC1516 will draw
between 200mA and 400mA from VIN causing a rise in
the junction temperature. On-chip thermal shutdown
circuitry disables the charge pump once the junction
temperature exceeds 135°C, and reenables the charge
pump once the junction temperature falls back to 115°C.
The LTC1516 will cycle in and out of thermal shutdown
indefinitely without latchup or damage until the VOUT short
is removed.
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 10µF or greater. If the
input source impedance is very low, CIN may not be
needed. Increasing the size of COUT to 22µF or greater will
reduce output voltage ripple.
Ceramic or tantalum capacitors are recommended for the
flying caps C1 and C2 with values in the range of 0.1µF to
1µF. Note that large value flying caps (> 0.22µF) will
increase output ripple unless COUT is also increased. For
very low load applications, C1 and C2 may be reduced to
0.01µF to 0.047µF. This will reduce output ripple at the
expense of efficiency and maximum output current.
higher ripple due to higher output voltage dV/dt. High ESR
capacitors (ESR > 0.5Ω) on the output pin cause high
frequency voltage spikes on VOUT with every clock cycle.
There are several ways to reduce the output voltage ripple.
A larger COUT capacitor (22µF or greater) will reduce both
the low and high frequency ripple due to the lower COUT
charging and discharging dV/dt and the lower ESR typically found with higher value (larger case size) capacitors.
A low ESR ceramic output capacitor will minimize the high
frequency ripple, but will not reduce the low frequency
ripple unless a high capacitance value is chosen. A reasonable compromise is to use a 10µF to 22µF tantalum
capacitor in parallel with a 1µF to 3.3µF ceramic capacitor
on VOUT to reduce both the low and high frequency ripple.
An RC filter may also be used to reduce high frequency
voltage spikes (see Figure 2).
In low load or high VIN applications, smaller values for C1
and C2 may be used to reduce output ripple. The smaller
C1 and C2 flying capacitors (0.022µF to 0.1µF) deliver less
charge per clock cycle to the output capacitor resulting in
lower output ripple. However, the smaller value flying caps
also reduce the maximum IOUT capability as well as
efficiency.
LTC1516
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VOUT
+
Output Ripple
Normal LTC1516 operation produces voltage ripple on the
VOUT pin. Output voltage ripple is required for the LTC1516
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 due to ESR (Equivalent Series
Resistance) in the output capacitor. Typical output ripple
under maximum load is 100mVP-P with a low ESR 10µF
output capacitor.
The magnitude of the ripple voltage depends on several
factors. High input voltages (VIN > 3.3V) increase the output
ripple since more charge is delivered to COUT per clock
cycle. Large C1 and C2 flying capacitors (> 0.22µF) also
increase ripple for the same reason. Large output current
load and/or a small output capacitor (< 10µF) results in
LTC1516
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VOUT
15µF
TANTALUM
1µF
CERAMIC
2Ω
+
VOUT
5V
+
10µF
VOUT
5V
10µF
1516 F02
Figure 2. Output Ripple Reduction Techniques
Inrush Currents
During normal operation, VIN will experience current transients in the 100mA to 200mA range whenever the charge
pump is enabled. During start-up, these inrush currents
may approach 500mA. For this reason, it is important to
minimize the source resistance between the input supply
and the VIN pin to prevent start-up problems and large
input voltage transients.
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LTC1516
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APPLICATIONS INFORMATION
Ultralow Quiescent Current (IQ < 5µA) Regulated
Supply
The LTC1516 contains an internal resistor divider (refer to
Block Diagram) which draws only 1.5µA (typ) from VOUT.
During no-load conditions, the internal load causes a
droop rate of only 150mV per second on VOUT with
COUT = 10µF. Applying a 5Hz to 100Hz, 95% to 98% duty
cycle signal to the SHDN pin ensures that the circuit of
Figure 3 comes out of shutdown frequently enough to
maintain regulation during no-load or low-load conditions. Since the part spends nearly all of its time in
shutdown, the no-load quiescent current (see Figure 4a) is
approximately equal to (VOUT)(1.5µA)/(VIN)(Efficiency).
The LTC1516 must be out of shutdown for a minimum
duration of 200µs to allow enough time to sense the output
and keep it in regulation. As the VOUT load current
increases, the frequency with which the part is taken out
of shutdown must also be increased to prevent VOUT
from drooping below 4.8V during the OFF phase (see
Figure 4b). A 100Hz 98% duty cycle signal on the SHDN
pin ensures proper regulation with load currents as high
as 100µA. When load current greater than 100µA is
needed, the SHDN pin must be forced low as in normal
operation. The typical no-load supply current for this
circuit with VIN = 3V is only 3.2µA.
0.22µF
1
VIN = 2V TO 5V
2
+
10µF
3
+
10µF 4
C1+
C1–
VIN
SHDN
LTC1516
VOUT
GND
C2+
C2 –
8
7
FROM MPU
SHDN PIN WAVEFORMS:
6
5
LOW IQ MODE (5Hz TO 100Hz, 95% TO 98% DUTY CYCLE) VOUT LOAD ENABLE MODE
IOUT ≤ 100µA
(IOUT = 100µA TO 50mA)
0.22µF
1516 • F03
VOUT = 5V ±4%
Figure 3. Ultralow Quiescent Current (<5µA) Regulated Supply
1000
MAXIMUM SHDN OFF TIME (ms)
SUPPLY CURRENT (µA)
6.0
4.0
2.0
0.0
2.0
100
10
1
3.0
4.0
INPUT VOLTAGE (V)
5.0
1516 • F04a
Figure 4a. No Load ICC vs Input Voltage for Circuit in Figure 3
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SHDN ON PULSE WIDTH = 200µs
COUT = 10µF
1
10
100
OUTPUT CURRENT (µA)
1000
1516 • F04b
Figure 4b. Maximum SHDN OFF Time vs Output Load Current for
Ultralow IQ Operation
LTC1516
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APPLICATIONS INFORMATION
Paralleling Devices
General Layout Considerations
Two or more LTC1516’s may be connected in parallel to
provide higher output currents. The VIN, VOUT, GND and
SHDN pins may be tied together, but the C1 and C2 pins
must be kept separate (see Figure 5). Separate CIN and
COUT capacitors may be required to reduce output noise
and ripple if the paralleled devices cannot be kept close
together. Otherwise, single CIN and COUT capacitors may
be used with each being 2× (or 3× if three parts are
paralleled, etc.) in value.
Due to the high switching frequency and high transient
currents produced by the LTC1516, careful board layout is
a must. A clean board layout using a ground plane and
short connections to all capacitors will improve performance and ensure proper regulation under all conditions
(refer to Figure 6).
C1
0.22µF
1
2
3
4
C1+
C1–
VIN
SHDN
LTC1516
VOUT
GND
C2+
C2 –
+
CIN
VIN
8
1
8
2
7
SHDN
LTC1516
VOUT
7
COUT
6
3
6
4
5
+
GND
5
C2
0.22µF
1516 • F06
Figure 6. Suggested Component Placement for LTC1516
0.22µF
1
VIN = 2V
TO 5V
2
+
22µF
3
+
22µF 4
C1+
C1–
VIN
SHDN
LTC1516
VOUT
GND
C2+
C2 –
8
7
ON/OFF
6
5
0.22µF
VOUT = 5V ±4%
IOUT = 0mA TO 40mA, VIN ≥ 2V
IOUT = 0mA TO 100mA, VIN ≥ 3V
1516 • F05
Figure 5. Paralleling Devices
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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LTC1516
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TYPICAL APPLICATIONS N
Fault-Protected SIM Interface Supply for
GSM Cellular Phones
Generating 5V and a Negative Supply
0.1µF
0.1µF
3V
C1–
8
VOUT
LTC1516
7
SHDN
GND
3
C1+
2 V
IN
+
10µF 4 C2+
C2 –
6
1
+
10µF
VOUT = 5V ±4%
IOUT = 40mA
ON/OFF
VIN
2V TO 5V
+
5
10µF
C1+
C1–
7
SHDN
VOUT
LTC1516
2
VIN
GND
4
C2+
0.1µF
C2 –
VOUT = 5V ± 4%
IOUT = 20mA,VIN ≥ 2V
IOUT = 50mA, VIN ≥ 3V
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3
240Ω
5
0.1µF
Q1
RST
CLK
**
SIM CARD
– VOUT = –1.4V TO – 3V
– IOUT = 5mA
10µF
*
VCC
Q2
3.3k
0.22µF
GSM
CONTROLLER
LEVEL SHIFT
8.2k
2.2µF
6
+
1
*CENTRAL SEMICONDUCTOR CMPSH-35 DUAL SCHOTTKY
**OPTIONAL CIRCUITRY FOR MAINTAINING – VOUT AT LOW VOUT LOADS
Q1, Q2: 2N3904
1516 • TA03
I/O
GND
1516 • TA02
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PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
8
0.004 – 0.010
(0.101 – 0.254)
7
5
6
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.050
(1.270)
BSC
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
SO8 0695
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PART NUMBER
DESCRIPTION
COMMENTS
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Provides – 4.1V at 20mA with <1mV Ripple
®
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Linear Technology Corporation
LT/GP 0796 7K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1996