Datasheet LM3352MTCX-3.3, LM3352MTCX-3.0, LM3352MTCX-2.5, LM3352MTC-3.0, LM3352MTC-2.5 Datasheet (NSC)

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 and3.3V.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 mAof 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 V

OUT

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

September 1999

LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter

© 1999 National Semiconductor Corporation DS101037 www.national.com

Connection Diagram

Ordering Information

Order Number Package Type NSC Package Drawing Supplied As

LM3352MTCX-2.5 TSSOP-16 MTC16 2.5k Units, Tape and Reel
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 Function

1 GND Ground

*

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
8V

OUT

Regulated Output Voltage

9 GND Ground

*

10 V

IN

Input Supply Voltage
11 NC This pin must be left unconnected.
12 GND Ground

*

13 SD Active Low CMOS Logic-Level Shutdown Input
14 GND Ground

*

15 C

FIL

Filter Capacitor;A1µFceramic capacitor is suggested.
16 GND Ground

*

*

All GND pins of the LM3352 must be connected to the same ground.

DS101037-2

Top View

TSSOP-16 Pin Package

See NS Package Number MTC16

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

V

OUT

Pin −0.5V to 4.5V
All Other Pins −0.5V to 5.6V
Power Dissipation (T

A

= 25˚C)

(Note 2) 700 mW

T

JMAX

(Note 2) 150˚C

θ

JA

(Note 2) 150˚C/W

Storage Temperature −65˚C to +150˚C

Lead Temperature (Soldering, 5 sec.) 260˚C
ESD Rating (Note 3)

human body model
machine model

2kV

100V

Operating Ratings

Input Voltage (VIN) 2.5V to 5.5V
Output Voltage (V

OUT

) 1.8V to 4.0V

Ambient Temperature (T

A

) (Note 2) −40˚C to +85˚C

Junction Temperature (T

J

) (Note 2) −40˚C to +125˚C

Electrical Characteristics

Limits in standard typeface are for T

J

=

25˚C, and limits in boldface type apply over the full operating temperature range. Unless

otherwise specified: C

1

=

C

2

=

C

3

=

0.33 µF; C

IN

=

15 µF; C

OUT

=

33 µF; V

IN

=

3.5V.

Parameter Conditions Min Typ Max Units

LM3352-2.5

Output Voltage (V

OUT

)V

IN

= 3.5V; I

LOAD

= 100 mA 2.463 2.5 2.537

V

2.8V

<

V

IN

<

5.5V;

1mA

<

I

LOAD

<

100 mA

2.425/2.400 2.5 2.575/2.600

3.6V

<

V

IN

<

4.9V;

1mA

<

I

LOAD

<

200 mA

2.425/2.400 2.5 2.575/2.600

4.9V

<

V

IN

<

5.5V;

1mA

<

I

LOAD

<

175 mA

2.425/2.400 2.5 2.575/2.600

Efficiency I

LOAD

=15mA 85

%

I

LOAD

= 150 mA, VIN= 4.0V 75

Output Voltage Ripple
(Peak-to-Peak)

I

LOAD

=50mA

C

OUT

= 33 µF tantalum

75 mV

P-P

LM3352-3.0

Output Voltage (V

OUT

)V

IN

= 3.5V; I

LOAD

= 100 mA 2.955 3.0 3.045

V

2.5V

<

V

IN

<

5.5V;

1mA

<

I

LOAD

<

100 mA

2.910/2.880 3.0 3.090/3.120

3.8V

<

V

IN

<

5.5V;

1mA

<

I

LOAD

<

200 mA

2.910/2.880 3.0 3.090/3.120

Efficiency I

LOAD

=15mA 80

%

I

LOAD

= 150 mA, VIN= 4.0V 75

Output Voltage Ripple
(Peak-to-Peak)

I

LOAD

=50mA

C

OUT

= 33 µF tantalum

75 mV

P-P

LM3352-3.3

Output Voltage (V

OUT

)V

IN

= 3.5V; I

LOAD

= 100 mA 3.251 3.3 3.349

V

2.5V

<

V

IN

<

5.5V;

1mA

<

I

LOAD

<

100 mA

3.201/3.168 3.3 3.399/3.432

4.0V

<

V

IN

<

5.5V;

1mA

<

I

LOAD

<

200 mA

3.201/3.168 3.3 3.399/3.432

Efficiency I

LOAD

=15mA 90

%

I

LOAD

= 150 mA, VIN= 4.0V 80

Output Voltage Ripple
(Peak-to-Peak)

I

LOAD

=50mA

C

OUT

= 33 µF tantalum

75 mV

P-P

LM3352-ALL OUTPUT VOLTAGE VERSIONS

Operating Quiescent Current Measured at Pin V

IN

;

I

LOAD

= 0A (Note 4)

400 500 µA

Shutdown Quiescent Current SD Pin at 0V (Note 5) 2.5 5 µA
Switching Frequency 0.65 1 1.35 MHz
SD Input Threshold Low 2.5V

<

V

IN

<

5.5V 0.2 V

IN

V

SD Input Threshold High 2.5V

<

V

IN

<

5.5V 0.8 V

IN

V

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Electrical Characteristics (Continued)

Limits in standard typeface are for T

J

=

25˚C, and limits in boldface type apply over the full operating temperature range. Un-

less otherwise specified: C

1

=

C

2

=

C

3

=

0.33 µF; C

IN

=

15 µF; C

OUT

=

33 µF; V

IN

=

3.5V.

Parameter Conditions Min Typ Max Units

LM3352-ALL OUTPUT VOLTAGE VERSIONS

SD Input Current Measured at SD Pin;

SD Pin = V

IN

= 5.5V

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 T

A

≤ +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 V

IN

>

5V with the 2.5V option, the junction temperature rise above ambient is: ∆T=540IL−23 where ILis in amps. The output current must be derated at

higher ambient temperatures to make sure T

J

does not exceed 150˚C when operating the 2.5V option at V

IN

>

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 di-
rectly into each pin.

Note 4: The V

OUT

pin is forced to 200 mV above the typical V

OUT

. This is to insure that the internal switches are off.

Note 5: The output capacitor C

OUT

is fully discharged before measurement.

Typical Performance Characteristics Unless otherwise specified T

A

=

25˚C.

V

OUT

vs. V

IN

DS101037-4

V

OUT

vs. V

IN

DS101037-5

V

OUT

vs. V

IN

DS101037-6

V

OUT

vs. V

IN

DS101037-7

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Typical Performance Characteristics Unless otherwise specified T

A

=

25˚C. (Continued)

V

OUT

vs. V

IN

DS101037-8

V

OUT

vs. V

IN

DS101037-9

V

OUT

vs. V

IN

DS101037-10

V

OUT

vs. V

IN

DS101037-11

V

OUT

vs. V

IN

DS101037-12

Load Transient Response

DS101037-14

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Typical Performance Characteristics Unless otherwise specified T

A

=

25˚C. (Continued)

Efficiency vs. V

IN

DS101037-20

Efficiency vs. V

IN

DS101037-21

Efficiency vs. V

IN

DS101037-22

Switching Frequency vs. V

IN

DS101037-23

Operating Quiescent
Current vs. V

IN

DS101037-24

V

OUT

Ripple vs. C

OUT

DS101037-30

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Typical Performance Characteristics Unless otherwise specified T

A

=

25˚C. (Continued)

Applications Information

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 V

OUT

through the comparator

COMP, the AND gate G

1

, the phase generator, and the

switch array. The comparator’s output is high when V

OUT

is

less than the reference V

REF

. 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

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.Thisdual loop provides regulation over a wide range of
loads efficiently.

Since efficiency is automatically optimized, the curves for
V

OUT

vs. VINand Efficiency vs. VINin 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.

Charge Pump Capacitor Selection

A0.33 µF ceramic capacitor is suggested for C1, C2 and C3.
To ensure proper operation over temperature variations, an
X7R dielectric material is recommended.

V

OUT

Ripple vs. C

OUT

DS101037-31

V

OUT

Ripple vs. C

OUT

DS101037-32

DS101037-3

FIGURE 1. Block Diagram

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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).

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

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.

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 tech-

nologies.

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
V

OUT

Ripple Magnitude

@

<

50 mA Low High Low

V

OUT

Ripple Magnitude

@

>

100 mA Low Slightly Higher Low

dv/dt of V

OUT

Ripple@All Loads Lowest High Low

b) CAPACITOR SELECTION

i) Output Capacitor (C

OUT

)

The output capacitor C

OUT

directly affects the magnitude of

the output ripple voltage so C

OUT

should be carefully se-

lected. The graphs titled V

OUT

Ripple vs. C

OUT

in the Typical
Performance Characteristics section show how the ripple
voltage magnitude is affected by the C

OUT

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 C

OUT

, the lower the output ripple magnitude. At

lighter loads, the low ESR ceramics offer a much lower V

OUT

ripple than the higher ESR tantalums of the same value. At
higher loads, the ceramics offer a slightly lower V

OUT

ripple
magnitude than the tantalums of the same value. However,
the dv/dt of the V

OUT

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.

ii) Input Capacitor (C

IN

)

The input capacitor C

IN

directly affects the magnitude of the

input ripple voltage, and to a lesser degree the V

OUT

ripple.

A higher value C

IN

will give a lower VINripple. 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 V

IN

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.

www.national.com 8

Filter Capacitor Selection (Continued)

iii) C

FIL

A 1 µF, XR7 ceramic capacitor should be connected to pin
C

FIL

. This capacitor provides the filtering needed for the in-

ternal supply rail of the LM3352.

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

.

TABLE 2. Capacitor Vendor Information

Manufacturer Tel Fax Website

Ceramic Taiyo-yuden [phone] [phone] www.t-yuden.com

AVX [phone] [phone] www.avxcorp.com

Tantalum Sprague/Vishay [phone] [phone] www.vishay.com

Nichicon [phone] [phone] www.nichicon.com

Polymer Electrolytic Cornell-Dubilier (ESRD) [phone] [phone] www.cornell-dubilier.com

Sanyo (POSCAP) [phone] [phone] www.sanyovideo.com

Maximum Available Output Current

The LM3352 cannot provide 200 mA under all VINand V

OUT

conditions. The V

OUT

vs VINgraphs in the Typical Perfor-

mance Characteristics section show the minimum V

IN

at
which the LM3352 is capable of providing different load cur­rents while maintaining V

OUT

regulation. Refer to the Electri-

cal Characteristics for guaranteed conditions.

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 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

).

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.

Typical Application Circuits

DS101037-33

FIGURE 2. Basic Buck/Boost Regulator

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Typical Application Circuits (Continued)

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 traces

between the capacitors and the IC short and direct. Use of a
ground plane is recommended.

Figure 4

shows a typical lay-

out as used in the LM3352 evaluation board.

DS101037-15

FIGURE 3. Low Output Noise and Ripple Buck/Boost Regulator

DS101037-16

FIGURE 4. Typical Layout, Top View (magnification 2.8X)

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Physical Dimensions inches (millimeters) unless otherwise noted

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can be reasonably expected to cause the failure of
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TSSOP-16 Pin Package

For Ordering, Refer to Ordering Information Table

NS Package Number MTC16

LM3352 Regulated 200 mA Buck-Boost Switched Capacitor DC/DC Converter

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.