LM3352
Regulated 200 mA Buck-Boost Switched Capacitor
DC/DC Converter
General Description
The LM3352 is a CMOS switched capacitor DC/DC converter that produces a regulated output voltage by automatically stepping up (boost) or stepping down (buck) the input
voltage. It accepts an input voltage between 2.5V and 5.5V.
The LM3352 is available in three standard output voltage
versions: 2.5V, 3.0V and 3.3V. If other output voltage options
between 1.8V and 4.0V are desired, please contact your
National Semiconductor representative.
The LM3352’s proprietary buck-boost architecture enables
up to 200 mA of load current at an average efficiency greater
than 80%. Typical operating current is only 400 µA and the
typical shutdown current is only 2.5 µA.
The LM3352 is available in a 16-pin TSSOP package. This
package has a maximum height of only 1.1 mm.
The high efficiency of the LM3352, low operating and shutdown currents, small package size, and the small size of the
overall solution make this device ideal for battery powered,
portable, and hand-held applications.
Features
n Regulated VOUT with ± 3% accuracy
n Standard output voltage options: 2.5V, 3.0V and 3.3V
n Custom output voltages available from 1.8V to 4.0V in
100 mV increments
n 2.5V to 5.5V input voltage
n Up to 200 mA output current
n > 80% average efficiency
n Uses few, low-cost external components
n Very small solution size
n 400 µA typical operating current
n 2.5 µA typical shutdown current
n 1 MHz switching frequency (typical)
n Architecture and control methods provide high load
current and good efficiency
n TSSOP-16 package
n Over-temperature protection
Applications
n 1-cell Lilon battery-operated equipment including PDAs,
hand-held PCs, cellular phones
n Flat panel displays
n Hand-held instruments
n NiCd, NiMH, or alkaline battery powered systems
n 3.3V to 2.5V and 5.0V to 3.3V conversion
Typical Operating Circuit
DS101037-1
© 2001 National Semiconductor Corporation
DS101037
www.national.com
LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter
September 1999
LM3352
Connection Diagram
DS101037-2
Top View
TSSOP-16 Pin Package
See NS Package Number MTC16
Ordering Information
Order Number
Package Type
LM3352MTCX-2.5
NSC Package Drawing
Supplied As
MTC16
2.5k Units, Tape and Reel
TSSOP-16
LM3352MTC-2.5
TSSOP-16
MTC16
94 Units, Rail
LM3352MTCX-3.0
TSSOP-16
MTC16
2.5k Units, Tape and Reel
LM3352MTC-3.0
TSSOP-16
MTC16
94 Units, Rail
LM3352MTCX-3.3
TSSOP-16
MTC16
2.5k Units, Tape and Reel
LM3352MTC-3.3
TSSOP-16
MTC16
94 Units, Rail
Pin Description
Pin Number
Name
1
GND
Ground*
Function
2
C3−
Negative Terminal for C3
3
C3+
Positive Terminal for C3
4
C2−
Negative Terminal for C2
5
C2+
Positive Terminal for C2
6
C1−
Negative Terminal for C1
7
C1+
Positive Terminal for C1
8
VOUT
Regulated Output Voltage
9
GND
Ground*
10
VIN
Input Supply Voltage
11
NC
This pin must be left unconnected.
12
GND
13
SD
Ground*
Active Low CMOS Logic-Level Shutdown Input
14
GND
Ground*
15
CFIL
Filter Capacitor; A 1 µF ceramic capacitor is suggested.
16
GND
Ground*
*All GND pins of the LM3352 must be connected to the same ground.
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2
Lead Temperature (Soldering, 5 sec.)
ESD Rating (Note 3)
human body model
machine model
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VOUT Pin
All Other Pins
Power Dissipation (TA = 25˚C)
(Note 2)
TJMAX (Note 2)
θJA (Note 2)
Storage Temperature
260˚C
2 kV
100V
Operating Ratings
−0.5V to 4.5V
−0.5V to 5.6V
Input Voltage (VIN)
Output Voltage (VOUT)
Ambient Temperature (TA) (Note 2)
Junction Temperature (T J) (Note 2)
700 mW
150˚C
150˚C/W
−65˚C to +150˚C
2.5V to 5.5V
1.8V to 4.0V
−40˚C to +85˚C
−40˚C to +125˚C
Electrical Characteristics
Limits in standard typeface are for TJ = 25˚C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: C1 = C2 = C3 = 0.33 µF; CIN = 15 µF; COUT = 33 µF; VIN = 3.5V.
Parameter
Conditions
Min
Typ
Max
Units
LM3352-2.5
Output Voltage (V
OUT)
Efficiency
Output Voltage Ripple
(Peak-to-Peak)
VIN = 3.5V; I
2.463
2.5
2.537
2.8V < VIN < 5.5V;
1 mA < ILOAD < 100 mA
2.425/2.400
2.5
2.575/2.600
3.6V < VIN < 4.9V;
1 mA < ILOAD < 200 mA
2.425/2.400
2.5
2.575/2.600
4.9V < VIN < 5.5V;
1 mA < ILOAD < 175 mA
2.425/2.400
2.5
2.575/2.600
LOAD
= 100 mA
ILOAD = 15 mA
85
ILOAD = 150 mA, VIN = 4.0V
75
ILOAD = 50 mA
C OUT = 33 µF tantalum
75
V
%
mVP-P
LM3352-3.0
Output Voltage (V
OUT)
VIN = 3.5V; I
LOAD
= 100 mA
2.5V < VIN < 5.5V;
1 mA < ILOAD < 100 mA
3.8V < VIN < 5.5V;
1 mA < ILOAD < 200 mA
Efficiency
Output Voltage Ripple
(Peak-to-Peak)
2.955
3.0
3.045
2.910/2.880
3.0
3.090/3.120
2.910/2.880
3.0
3.090/3.120
ILOAD = 15 mA
80
ILOAD = 150 mA, VIN = 4.0V
75
ILOAD = 50 mA
C OUT = 33 µF tantalum
75
V
%
mVP-P
LM3352-3.3
Output Voltage (V
OUT)
Efficiency
Output Voltage Ripple
(Peak-to-Peak)
VIN = 3.5V; I
3.251
3.3
3.349
2.5V < VIN < 5.5V;
1 mA < ILOAD < 100 mA
3.201/3.168
3.3
3.399/3.432
4.0V < VIN < 5.5V;
1 mA < ILOAD < 200 mA
3.201/3.168
3.3
3.399/3.432
LOAD
= 100 mA
ILOAD = 15 mA
90
ILOAD = 150 mA, VIN = 4.0V
80
ILOAD = 50 mA
C OUT = 33 µF tantalum
75
V
%
mVP-P
LM3352-ALL OUTPUT VOLTAGE VERSIONS
Operating Quiescent Current
Measured at Pin VIN;
I LOAD = 0A (Note 4)
Shutdown Quiescent Current
SD Pin at 0V (Note 5)
400
Switching Frequency
SD Input Threshold Low
0.65
2.5V < VIN < 5.5V
3
500
µA
2.5
5
µA
1
1.35
MHz
0.2 VIN
V
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LM3352
Absolute Maximum Ratings (Note 1)
LM3352
Electrical Characteristics
(Continued)
Limits in standard typeface are for TJ = 25˚C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: C1 = C2 = C3 = 0.33 µF; CIN = 15 µF; COUT = 33 µF; VIN = 3.5V.
Parameter
Conditions
Min
Typ
Max
Units
LM3352-ALL OUTPUT VOLTAGE VERSIONS
SD Input Threshold High
2.5V < VIN < 5.5V
SD Input Current
Measured at SD Pin;
SD Pin = VIN = 5.5V
0.8 VIN
V
0.1
1.0
µA
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating conditions.
Note 2: As long as TA ≤ +85˚C, all electrical characteristics hold true for the 3.0V and 3.3V options at all current loads and the 2.5V option at all loads when VIN
≤ 5V. For VIN > 5V with the 2.5V option, the junction temperature rise above ambient is: ∆T = 540IL−23 where IL is in amps. The output current must be derated
at higher ambient temperatures to make sure TJ does not exceed 150˚C when operating the 2.5V option at VIN > 5V.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged
directly into each pin.
Note 4: The VOUT pin is forced to 200 mV above the typical VOUT. This is to insure that the internal switches are off.
Note 5: The output capacitor COUT is fully discharged before measurement.
Typical Performance Characteristics
Unless otherwise specified TA = 25˚C.
VOUT vs. VIN
VOUT vs. VIN
DS101037-4
VOUT vs. VIN
DS101037-5
VOUT vs. VIN
DS101037-6
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DS101037-7
4
Unless otherwise specified TA = 25˚C. (Continued)
VOUT vs. VIN
VOUT vs. VIN
DS101037-8
VOUT vs. VIN
LM3352
Typical Performance Characteristics
DS101037-9
VOUT vs. VIN
DS101037-10
VOUT vs. VIN
DS101037-11
Load Transient Response
DS101037-12
DS101037-14
5
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LM3352
Typical Performance Characteristics
Unless otherwise specified TA = 25˚C. (Continued)
Efficiency vs. VIN
Efficiency vs. VIN
DS101037-20
Efficiency vs. VIN
DS101037-21
Switching Frequency vs. VIN
DS101037-23
DS101037-22
Operating Quiescent
Current vs. VIN
VOUT Ripple vs. COUT
DS101037-30
DS101037-24
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6
Unless otherwise specified TA = 25˚C. (Continued)
VOUT Ripple vs. COUT
VOUT Ripple vs. COUT
DS101037-31
LM3352
Typical Performance Characteristics
DS101037-32
Applications Information
DS101037-3
FIGURE 1. Block Diagram
gains based on inputs from the A/D and the comparator. The
gain signal is sent to the phase generator which then sends
the appropriate timing and configuration signals to the switch
array. This dual loop provides regulation over a wide range of
loads efficiently.
Since efficiency is automatically optimized, the curves for
VOUT vs. VIN and Efficiency vs. VIN in the Typical Performance Characteristics section exhibit small variations. The
reason is that as input voltage or output load changes, the
digital control loops are making decisions on how to optimize
efficiency. As the switch array is reconfigured, small variations in output voltage and efficiency result. In all cases
where these small variations are observed, the part is operating correctly; minimizing output voltage changes and optimizing efficiency.
Operating Principle
The LM3352 is designed to provide a step-up/step-down
voltage regulation in battery powered systems. It combines
switched capacitor circuitry, reference, comparator, and
shutdown logic in a single 16-pin TSSOP package. The
LM3352 can provide a regulated voltage between 1.8V and
4V from an input voltage between 2.5V and 5.5V. It can
supply a load current up to 200 mA.
As shown in Figure 1, the LM3352 employs two feedback
loops to provide regulation in the most efficient manner
possible. The first loop is from VOUT through the comparator
COMP, the AND gate G1, the phase generator, and the
switch array. The comparator’s output is high when VOUT is
less than the reference VREF. Regulation is provided by
gating the clock to the switch array. In this manner, charge is
transferred to the output only when needed. The second
loop controls the gain configuration of the switch array. This
loop consists of the comparator, the digital control block, the
phase generator, and the switch array. The digital control
block computes the most efficient gain from a set of seven
Charge Pump Capacitor Selection
A 0.33 µF ceramic capacitor is suggested for C1, C2 and C3.
To ensure proper operation over temperature variations, an
X7R dielectric material is recommended.
7
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LM3352
choice for low ripple, high frequency applications. However,
the temperature stability of the ceramics is bad, except for
the X7R and X5R dielectric types. High capacitance values
( > 1 µF) are achievable from companies such as
Taiyo-yuden which are suitable for use with regulators. Ceramics are taller and larger than the tantalums of the same
capacitance value.
Filter Capacitor Selection
a) CAPACITOR TECHNOLOGIES
The three major technologies of capacitors that can be used
as filter capacitors for LM3352 are: i) tantalum, ii) ceramic
and iii) polymer electrolytic technologies.
i) Tantalum
Tantalum capacitors are widely used in switching regulators.
Tantalum capacitors have the highest CV rating of any technology; as a result, high values of capacitance can be obtained in relatively small package sizes. It is also possible to
obtain high value tantalum capacitors in very low profile
( < 1.2 mm) packages. This makes the tantalums attractive
for low-profile, small size applications. Tantalums also possess very good temperature stability; i.e., the change in the
capacitance value, and impedance over temperature is relatively small. However, the tantalum capacitors have relatively
high ESR values which can lead to higher voltage ripple and
their frequency stability (variation over frequency) is not very
good, especially at high frequencies ( > 1 MHz).
iii) Polymer Electrolytic
Polymer electrolytic is a third suitable technology. Polymer
capacitors provide some of the best features of both the
ceramic and the tantalum technologies. They provide very
low ESR values while still achieving high capacitance values. However, their ESR is still higher than the ceramics,
and their capacitance value is lower than the tantalums of
the same size. Polymers offer good frequency stability (comparable to ceramics) and good temperature stability (comparable to tantalums). The Aluminum Polymer Electrolytics
offered by Cornell-Dubilier and Panasonic, and the POSCAPs offered by Sanyo fall under this category.
Table 1 compares the features of the three capacitor technologies.
ii) Ceramic
Ceramic capacitors have the lowest ESR of the three technologies and their frequency stability is exceptionally good.
These characteristics make the ceramics an attractive
TABLE 1. Comparison of Capacitor Technologies
Ceramic
Tantalum
Polymer
Electrolytic
ESR
Lowest
High
Low
Relative Height
Low for Small Values ( < 10 µF); Taller for
Higher Values
Lowest
Low
Relative Footprint
Large
Small
Largest
Temperature Stability
X7R/X5R-Acceptable
Good
Good
Frequency Stability
Good
Acceptable
Good
VOUT Ripple Magnitude @ < 50 mA
Low
High
Low
VOUT Ripple Magnitude @ > 100 mA
Low
Slightly Higher
Low
dv/dt of VOUT Ripple @ All Loads
Lowest
High
Low
ii) Input Capacitor (CIN)
b) CAPACITOR SELECTION
The input capacitor CIN directly affects the magnitude of the
input ripple voltage, and to a lesser degree the VOUT ripple.
A higher value CIN will give a lower VIN ripple. To optimize
low input and output ripple as well as size a 15 µF polymer
electrolytic, 22 µF ceramic, or 33 µF tantalum capacitor is
recommended. This will ensure low input ripple at 200 mA
load current. If lower currents will be used or higher input
ripple can be tolerated then a smaller capacitor may be used
to reduce the overall size of the circuit. The lower ESR
ceramics and polymer electrolytics achieve a lower VIN
ripple than the higher ESR tantalums of the same value.
Tantalums make a good choice for small size, very low
profile applications. The ceramics and polymer electrolytics
are a good choice for low ripple, low noise applications
where size is less of a concern. The 15 µF polymer electrolytics are physically much larger than the 33 µF tantalums
and 22 µF ceramics.
i) Output Capacitor (COUT)
The output capacitor COUT directly affects the magnitude of
the output ripple voltage so COUT should be carefully selected. The graphs titled VOUT Ripple vs. COUT in the Typical
Performance Characteristics section show how the ripple
voltage magnitude is affected by the COUT value and the
capacitor technology. These graphs are taken at the gain at
which worst case ripple is observed. In general, the higher
the value of COUT, the lower the output ripple magnitude. At
lighter loads, the low ESR ceramics offer a much lower VOUT
ripple than the higher ESR tantalums of the same value. At
higher loads, the ceramics offer a slightly lower VOUT ripple
magnitude than the tantalums of the same value. However,
the dv/dt of the VOUT ripple with the ceramics and polymer
electrolytics is much lower than the tantalums under all load
conditions. The tantalums are suggested for very low profile,
small size applications. The ceramics and polymer electrolytics are a good choice for low ripple, low noise applications
where size is less of a concern.
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8
Of the different capacitor technologies, a sample of vendors
that have been verified as suitable for use with the LM3352
are shown in Table 2.
(Continued)
iii) CFIL
A 1 µF, XR7 ceramic capacitor should be connected to pin
CFIL. This capacitor provides the filtering needed for the
internal supply rail of the LM3352.
TABLE 2. Capacitor Vendor Information
Manufacturer
Ceramic
Tantalum
Polymer Electrolytic
Tel
Fax
Taiyo-yuden
(408) 573-4150
(408) 573-4159
www.t-yuden.com
Website
AVX
(803) 448-9411
(803) 448-1943
www.avxcorp.com
Sprague/Vishay
(207) 324-4140
(207) 324-7223
www.vishay.com
Nichicon
(847) 843-7500
(847) 843-2798
www.nichicon.com
Cornell-Dubilier (ESRD)
(508) 996-8561
(508) 996-3830
www.cornell-dubilier.com
Sanyo (POSCAP)
(619) 661-6322
(619) 661-1055
www.sanyovideo.com
Reset circuit, such as the LP3470, is recommended if
greater start up loads are expected. Under certain conditions
the LM3352 can start up with greater load currents without
the use of a Power On Reset Circuit (See application note
AN-1144: Maximizing Startup Loads with the LM3352 Regulated Buck/Boost Switched Capacitor Converter).
Maximum Available Output Current
The LM3352 cannot provide 200 mA under all VIN and VOUT
conditions. The VOUT vs VIN graphs in the Typical Performance Characteristics section show the minimum VIN at
which the LM3352 is capable of providing different load
currents while maintaining VOUT regulation. Refer to the
Electrical Characteristics for guaranteed conditions.
Thermal Protection
During output short circuit conditions, the LM3352 will draw
high currents causing a rise in the junction temperature.
On-chip thermal protection circuitry disables the charge
pump action once the junction temperature exceeds the
thermal trip point, and re-enables the charge pump when the
junction temperature falls back to a safe operating point.
Maximum Load Under Start-Up
Due to the LM3352’s unique start-up sequence, it is not able
to start up under all load conditions. Starting with 45 mA or
less will allow the part to start correctly under any temperature or input voltage conditions. After the output is in regulation, any load up to the maximum as specified in the
Electrical Characteristics may be applied. Using a Power On
Typical Application Circuits
DS101037-33
FIGURE 2. Basic Buck/Boost Regulator
9
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LM3352
Filter Capacitor Selection
LM3352
Typical Application Circuits
(Continued)
DS101037-15
FIGURE 3. Low Output Noise and Ripple Buck/Boost Regulator
traces between the capacitors and the IC short and direct.
Use of a ground plane is recommended. Figure 4 shows a
typical layout as used in the LM3352 evaluation board.
Layout Considerations
Due to the 1 MHz typical switching frequency of the LM3352,
careful board layout is a must. It is important to place the
capacitors as close to the IC as possible and to keep the
DS101037-16
FIGURE 4. Typical Layout, Top View (magnification 2.8X)
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10
inches (millimeters) unless otherwise noted
TSSOP-16 Pin Package
For Ordering, Refer to Ordering Information Table
NS Package Number MTC16
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LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter
Physical Dimensions