LTC1522 - Micropower, Regulated 5V Charge Pump DC/DC Converter

LTC1522
Micropower, Regulated
5V Charge Pump
DC/DC Converter
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DESCRIPTION
FEATURES
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Ultralow Power: Typical Operating ICC = 6µA
Short-Circuit/Thermal Protected
Regulated 5V ±4% Output Voltage
2.7V to 5V Input Range
No Inductors
Very Low ICC in Shutdown: < 1µA
Output Current: 10mA (VIN ≥ 2.7V)
20mA (VIN ≥ 3V)
Shutdown Disconnects Load from VIN
Internal Oscillator: 700kHz
Compact Application Circuit (< 0.1 in2)
8-Pin MSOP and SO Packages
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APPLICATIONS
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SIM Interface Supplies for GSM Cellular Telephones
Li-Ion Battery Backup Supplies
Local 3V to 5V Conversion
Smart Card Readers
PCMCIA Local 5V Supplies
The LTC1522 has thermal shutdown and can survive a
continuous short from VOUT to GND. In shutdown the
load is disconnected from VIN. The part is available in
8-pin MSOP and SO packages. The LTC1522 is pin
compatible with the LTC1516 in applications where
VIN ≥ 2.7V and IOUT ≤ 20mA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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The LTC®1522 is a micropower charge pump DC/DC
converter that produces a regulated 5V output from a 2.7V
to 5V input supply. Extremely low supply current (6µA
typical with no load, < 1µA in shutdown) and low external
parts count (one 0.22µF flying capacitor and two 10µF
capacitors at VIN and VOUT) make the LTC1522 ideally
suited for small, light load battery-powered applications.
Typical efficiency (VIN = 3V) exceeds 75% with load
currents between 50µA and 20mA. Modulating the SHDN
pin keeps the typical efficiency above 75% with load
currents all the way down to 10µA.
TYPICAL APPLICATION
Regulated 5V Output from a 2.7V to 5V Input
1
+
10µF
2
3
+
10µF 4
NC
NC
VIN
SHDN
LTC1522
VOUT
GND
C+
C–
8
7
VIN = 3V
ON/OFF
6
5
0.22µF
VOUT = 5V ±4%
IOUT = 0mA TO 10mA, VIN ≥ 2.7V
IOUT = 0mA TO 20mA, VIN ≥ 3V
80
EFFICIENCY (%)
VIN
2.7V TO 5V
Efficiency vs Output Current
90
LOW IQ MODE
(SEE FIGURE 2)
70
SHDN = 0V
60
1522 TA01
50
0.01
0.1
1
10
OUTPUT CURRENT (mA)
100
1522 TA02
1
LTC1522
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ABSOLUTE MAXIMUM RATINGS
(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
Commercial Temperature Range ................ 0°C to 70°C
Extended Commercial Operating
Temperature Range (Note 2) ............. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
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PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
NC 1
VIN 2
VOUT 3
C+ 4
8
7
6
5
NC
SHDN
GND
C–
MS8 PACKAGE
8-LEAD PLASTIC MSOP
LTC1522CMS8
ORDER PART
NUMBER
TOP VIEW
NC 1
8 NC
VIN 2
7 SHDN
C+ 4
MS8 PART MARKING
TJMAX = 125°C, θJA = 160°C/ W
LTCG
LTC1522CS8
6 GND
VOUT 3
5 C–
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
1522
TJMAX = 125°C, θJA = 150°C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
VIN = 2.7V to 5V, CFLY = 0.22µF, CIN = COUT = 10µF, TMIN to TMAX unless otherwise specified. (Note 2)
SYMBOL PARAMETER
VIN
Input Voltage
VOUT
Output Voltage
ICC
fOSC
VIH
VIL
IIH
IIL
tON
Operating Supply Current
Shutdown Supply Current
Output Ripple
Efficiency
Switching Frequency
SHDN Input Threshold
CONDITIONS
●
2.7V ≤ VIN ≤ 5V, IOUT ≤ 10mA
3V ≤ VIN ≤ 5V, IOUT ≤ 20mA
2.7V ≤ VIN ≤ 5V, IOUT = 0mA, SHDN = 0V
2.7V ≤ VIN ≤ 3.6V, IOUT = 0mA, SHDN = VIN
3.6V < VIN ≤ 5V, IOUT = 0mA, SHDN = VIN
VIN = 3V, IOUT = 10mA
VIN = 3V, IOUT = 10mA
Oscillator Free Running
●
●
●
VOUT Turn-On Time
5.0
5.0
6
0.005
VSHDN = VIN
VSHDN = 0V
VIN = 3V, IOUT = 0mA
MAX
5
5.2
5.2
15
1
2.5
70
82
700
●
SHDN Input Current
TYP
(0.7)(VIN)
●
The ● denotes specifications which apply over the specified temperature
range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
2
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●
MIN
2.7
4.8
4.8
●
●
0.4
–1
–1
1
1
1
UNITS
V
V
V
µA
µA
µA
mVP-P
%
kHz
V
V
µA
µA
ms
Note 2: C grade device specifications are guaranteed over the 0°C to 70°C
temperature range. In addition, C grade device specifications are assured
over the – 40°C to 85°C temperature range by design or correlation, but
are not production tested.
LTC1522
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TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage vs Input Voltage
Efficiency vs Input Voltage
250
IOUT = 10mA
TA = 25°C
IOUT = 10mA
COUT = 10µF
80
5.05
TA = 70°C
5.00
TA = 0°C
TA = 25°C
70
60
50
4.95
4.90
2.5
3.0
4.0
4.5
3.5
INPUT VOLTAGE (V)
3.0
4.0
4.5
3.5
INPUT VOLTAGE (V)
No Load Input Current
vs Input Voltage
5.2
OUTPUT VOLTAGE (V)
8
TA = 25°C
TA = 0°C
5
4
2.5
4.0
4.5
3.5
INPUT VOLTAGE (V)
5.0
3.0
4.0
4.5
3.5
INPUT VOLTAGE (V)
Load Transient Response
IOUT
0mA TO 10mA
10mA/DIV
5.1
VOUT
AC COUPLED
50mV/DIV
5.0
VIN = 2.7V
4.9
4.8
0
VIN = 3V
40
60
20
OUTPUT CURRENT (mA)
1522 G04
5.0
1522 G03
VIN = 3.3V
3.0
COUT = 22µF
0
2.5
5.0
TA = 25°C
CFLY = 0.1µF
COUT = 6.8µF
IOUT = 0mA
6
COUT = 10µF
Typical Output Voltage
vs Output Current
9
TA = 70°C
COUT = 6.8µF
100
1522 G02
1522 G01
7
COUT = 3.3µF
150
50
40
2.5
5.0
IOUT = 10mA
CFLY = 0.1µF
TA = 25°C
200
VRIPPLE P-P (mV)
EFFICIENCY (%)
OUTPUT VOLTAGE (V)
5.10
INPUT CURRENT (µA)
Output Ripple vs Input Voltage
90
5.15
VIN = 3V
COUT = 10µF
500µs/DIV
1522 G06
80
1522 G05
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PIN FUNCTIONS
NC (Pin 1): No Connect.
C – (Pin 5): Flying Capacitor, Negative Terminal.
VIN (Pin 2): Input Supply Voltage. Bypass VIN with a
≥ 3.3µF low ESR capacitor.
GND (Pin 6): Ground.
VOUT (Pin 3): 5V Output Voltage (VOUT = 0V in Shutdown).
Bypass VOUT with a ≥ 3.3µF low ESR capacitor.
SHDN (Pin 7): Active High CMOS Logic-Level Shutdown
Input. Drive SHDN low to enable the DC/DC converter. Do
not float.
C + (Pin 4): Flying Capacitor, Positive Terminal.
NC (Pin 8): No Connect.
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LTC1522
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BLOCK DIAGRAM
VIN
CIN
10µF
SHDN
+
S2A
+
S1A
+
C
1µA
CFLY
0.22µF
S2B
S1B
CLOCK 2
CHARGE PUMP
COUT
10µF
COMP1
CLOCK 1
C–
VOUT
+
CONTROL
LOGIC
–
VREF
LTC1522 BD
CHARGE PUMP SHOWN IN DISCHARGE CYCLE
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APPLICATIONS INFORMATION
Operation
The LTC1522 uses a switched capacitor charge pump to
boost VIN 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 COMP1. When the charge pump is enabled, a 2-phase,
nonoverlapping clock controls the charge pump switches.
Clock 1 closes the S1 switches which enables the flying
capacitor to charge up to the VIN voltage. Clock 2 closes
the S2 switches that stack CFLY in series with VIN and
connect the top plate of CFLY to the output capacitor at
VOUT. This sequence of charging and discharging continues at a free-running frequency of 700kHz (typ) until the
output has risen to the upper trip point of COMP1 and the
charge pump is disabled. When the charge pump is
disabled, the LTC1522 draws only 4µA (typ) from VIN
which provides high efficiency at low load conditions.
In shutdown mode, all circuitry is turned off and the part
draws only leakage current 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
4
high is applied to the SHDN pin. The SHDN pin should not
be floated; it must be driven with a logic high or low.
Short-Circuit/Thermal Protection
During short-circuit conditions, the LTC1522 will draw
between 100mA and 200mA from VIN causing a rise in
the junction temperature. On-chip thermal shutdown
circuitry disables the charge pump once the junction
temperature exceeds ≈ 160°C, and reenables the charge
pump once the junction temperature falls back to ≈ 145°C.
The LTC1522 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
(< 0.5Ω) 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 (aluminum capacitors are not recommended
because of their high ESR). If the input source impedance
is very low, CIN may not be needed. Increasing the size of
COUT to 10µF or greater will reduce output voltage ripple.
LTC1522
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APPLICATIONS INFORMATION
A ceramic capacitor is recommended for the flying capacitor with a value in the range of 0.1µF to 0.22µF. Note that
a large value flying cap (> 0.22µF) will increase output
ripple unless COUT is also increased. For very low load
applications, CFLY may be reduced to 0.01µF to 0.047µF.
This will reduce output ripple at the expense of efficiency
and maximum output current.
LTC1522
3
VOUT
LTC1522
3
VOUT
+
15µF
TANTALUM
1µF
CERAMIC
3.9Ω
+
10µF
TANTALUM
+
VOUT
5V
10µF
TANTALUM
1522 F01
Output Ripple
Normal LTC1522 operation produces voltage ripple on the
VOUT pin. Output voltage ripple is required for the LTC1522
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 50mVP-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. A large flying capacitor (> 0.22µF) also increases
ripple for the same reason. Large output current load and/
or a small output capacitor (< 10µF) results in 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 1).
VOUT
5V
Figure 1. Output Ripple Reduction Techniques
In low load or high VIN applications, smaller values for
CFLY may be used to reduce output ripple. A smaller flying
capacitor (0.01µF to 0.047µF) delivers 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.
Inrush Currents
During normal operation, VIN will experience current transients in the 50mA to 100mA range whenever the charge
pump is enabled. During start-up, these inrush currents
may approach 250mA. For this reason, it is important to
minimize the source resistance between the input supply
and the VIN pin. Too much source resistance may result in
regulation problems or even prevent start-up.
Ultralow Quiescent Current (IQ = 2.1µA)
Regulated Supply
The LTC1522 contains an internal resistor divider (refer to
the Block Diagram) that draws only 1µA (typ) from VOUT.
During no-load conditions, the internal load causes a
droop rate of only 100mV per second on VOUT with
COUT = 10µF. Applying a 2Hz to 100Hz, 95% to 98% duty
cycle signal to the SHDN pin ensures that the circuit of
Figure 2 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 3a) is
approximately equal to (VOUT)(1µA)/(VIN)(Efficiency).
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LTC1522
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APPLICATIONS INFORMATION
1
VIN
2.7V TO 5V
2
+
10µF
3
+
10µF 4
NC
NC
VIN
SHDN
LTC1522
VOUT
GND
C+
C–
8
7
FROM MPU
SHDN PIN WAVEFORMS:
6
5
LOW IQ MODE (2Hz TO 100Hz, 95% TO 98% DUTY CYCLE) VOUT LOAD ENABLE MODE
IOUT ≤ 100µA
(IOUT = 100µA TO 20mA)
0.22µF
1522 F02
VOUT
5V ±4%
Figure 2. Ultralow Quiescent Current (<2.1µA) Regulated Supply
1000
MAXIMUM SHDN OFF TIME (ms)
SUPPLY CURRENT (µA)
6.0
4.0
2.0
0.0
2.0
SHDN ON PULSE WIDTH = 200µs
COUT = 10µF
100
10
1
3.0
4.0
INPUT VOLTAGE (V)
5.0
1522 F03a
1
10
100
OUTPUT CURRENT (µA)
1000
1522 F03b
Figure 3a. No-Load ICC vs Input Voltage for Circuit in Figure 3
Figure 3b. Maximum SHDN OFF Time vs Output Load Current
for Ultralow IQ Operation
The LTC1522 must be out of shutdown for a minimum
duration of 200µs to allow enough time to sense the output
and keep it in regulation. A 2Hz, 98% duty cycle signal will
keep VOUT in regulation under no-load conditions. 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 3b). 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 2.1µA.
Each time the LTC1522 comes out of shutdown, the part
delivers a minimum of one clock cycle worth of charge to
the output. Under high VIN (> 3.3V) and/or low IOUT (< 10µA)
conditions, this behavior may cause a net excess of charge
to be delivered to the output capacitor if a high frequency
signal is used on the SHDN pin (e.g., 50Hz to 100Hz).
Under such conditions, VOUT will slowly drift positive and
may even go out of regulation. To avoid this potential
problem in the low IQ mode, it is necessary to switch the
part in and out of shutdown at the minimum allowable
frequency (refer to Figure 3b) for a given output load.
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LTC1522
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APPLICATIONS INFORMATION
General Layout Considerations
Due to the high switching frequency and high transient
currents produced by the LTC1522, careful board layout
is a must. A clean board layout using a ground plane and
CIN
+
VIN
1
short connections to all capacitors will improve performance and ensure proper regulation under all conditions
(refer to Figure 4).
8
2
7
SHDN
LTC1522
VOUT
3
6
4
5
+
COUT
GND
CFLY
1522 F04
Figure 4. Suggested Component Placement for LTC1522
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PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.034 ± 0.004
(0.86 ± 0.102)
8
7 6
5
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
TYP
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.118 ± 0.004**
(3.00 ± 0.102)
0.192 ± 0.004
(4.88 ± 0.10)
MSOP (MS8) 1197
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* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
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2 3
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)
0.053 – 0.069
(1.346 – 1.752)
0.008 – 0.010
(0.203 – 0.254)
0.004 – 0.010
(0.101 – 0.254)
8
7
6
5
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)
TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
SO8 0996
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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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LTC1522
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TYPICAL APPLICATION
Programmable 5V/3V SIM Interface Supply for GSM Cellular Phones
D1
Q1
3V
R1
470k
A
1
2
B
+
TRUTH TABLE
A B
V CC
0
0 NOT USED
0
1
3V
1
0
5V
1
1 SHUTDOWN
7
NC
NC
VIN
VOUT
LTC1522
SHDN
GND
10µF 4 C +
GSM
CONTROLLER
C–
8
3
+
6
10µF
VCC = 5V OR 3V
(SEE TRUTH TABLE)
D1 = BAS70-05
Q1 = Si6943DQ
5
0.22µF
VCC
RST
LEVEL SHIFT
CLK
SIM CARD
I/O
GND
1522 TA03
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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20mA Switched Capacitor Converter for Up to 20V Inputs
Includes Micropower Shutdown (8µA)
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5V to 12V Regulated Switched Capacitor Converter
Up to 30mA at Regulated Output
LTC1514/15
Step-Up/Step-Down Switched Capacitor DC/DC Converters
VIN 2V to 10V, VOUT is Fixed or Adjustable, IOUT to 50mA
LTC1516
Micropower, Regulated 5V Charge Pump DC/DC Converter
IOUT = 20mA (VIN ≥ 2V), IOUT = 50mA (VIN ≥ 3V)
LTC1517-5
Micropower, Regulated 5V Charge Pump DC/DC Converter
LTC1522 Without Shutdown and Packaged in SOT-23
LTC1555/56
SIM Power Supply and Level Translator
Step-Up/Step-Down SIM Power Supply and Level Translators
LTC660
100mA CMOS Voltage Converter
5V to – 5V Conversion with Low Voltage Loss
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900
FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com
1522f LT/TP 0198 4K • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 1997