Datasheet LM2665M6, LM2665M6X Datasheet (NSC)

LM2665
Switched Capacitor Voltage Converter

LM2665 Switched Capacitor Voltage Converter

November 1999

General Description

The LM2665 CMOS charge-pump voltage converter oper­ates asa voltage doubler for an input voltage in the range of
+2.5V to +5.5V. Two low cost capacitors and a diode
(needed during start-up) are used in this circuit to provide up
to 40 mA of output current. The LM2665 can also work as a
voltage divider to split a voltage in the range of +1.8V to
+11V in half.

The LM2665 operates at 160 kHz oscillator frequency to re­duce output resistance and voltage ripple. With an operating
current of only650 µA (operating efficiency greaterthan 90
with most loads) and 1µA typical shutdown current, the
LM2665 provides ideal performance for battery powered
systems. The device is in SOT-23-6 package.

Basic Application Circuits

Voltage Doubler

Splitting Vinin Half

Features

n Doubles or Splits Input Supply Voltage
n SOT23-6 Package
n 12Ω Typical Output Impedance
n 90%Typical Conversion Efficiency at 40 mA
n 1µA Typical Shutdown Current

Applications

n Cellular Phones
n Pagers

%

n PDAs
n Operational Amplifier Power Suppliers
n Interface Power Suppliers
n Handheld Instruments

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© 1999 National Semiconductor Corporation DS100049 www.national.com

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

LM2665

please contact theNational Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage (V+ to GND, or GND to OUT) 5.8V
SD (GND − 0.3V) to (V+ +

V+ and OUT Continuous Output Current 50 mA
Output Short-Circuit Duration to GND (Note 2) 1 sec.

0.3V)

Continuous Power
Dissipation (T

T

(Note 3) 150˚C

JMax

θ

(Note 3) 210˚C/W

JA

Operating Junction

=

25˚C)(Note 3)

A

−40˚ to 85˚C

Temperature Range
Storage Temperature Range −65˚C to +150˚C
Lead Temp. (Soldering, 10 seconds) 300˚C
ESD Rating 2kV

Electrical Characteristics

Limits in standard typeface are for T
less otherwise specified: V+=5V, C

Symbol Parameter Condition Min Typ Max Units

V+ Supply Voltage 2.5 5.5 V
I

Q

I

SD

V

SD

I

L

R

SW

R

OUT

f

OSC

f

SW

P

EFF

V

OEFF

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: OUTmay be shorted to GND for onesecond without damage. However, shorting OUT to V+ may damage the device and should be avoided.Also, for tem­peratures above 85˚C, OUT must not be shorted to GND or V+, or device may be damaged.

Note 3: The maximum allowable power dissipation is calculated by using P
ambient temperature, and θ

Note 4: Inthetestcircuit, capacitors C
voltage and efficiency.

Note 5: The minimum input high for the shutdown pin equals 40%of V+.
Note 6: The maximum input low of the shutdown pin equals 20%of V+.
Note 7: Specifiedoutputresistance includes internal switch resistance and capacitor ESR. See thedetails in the application information for positive voltage doubler.
Note 8: The output switches operate at one half of the oscillator frequency, f

Supply Current No Load 650 1250 µA
Shutdown Supply Current 1 µA
Shutdown Pin Input Voltage Shutdown Mode 2.0

Output Current 40 mA
Sum of the R

internal MOSFET switches

ds(on)

Output Resistance (Note 7) I
Oscillator Frequency (Note 8) 80 160 kHz
Switching Frequency (Note 8) 40 80 kHz
Power Efficiency RL(1.0k) between GND and

Voltage Conversion Efficiency No Load 99 99.96

is the junction-to-ambient thermal resistance of the specified package.

JA

=

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

J

=

=

C

3.3 µF. (Note 4)

1

2

(Note 5)

Normal Operation 0.8

(Note 6)

of the four

and C2are 3.3 µF, 0.3Ω maximum ESR capacitors. CapacitorswithhigherESRwillincreaseoutput resistance, reduce output

1

=

I

40 mA 3.5 8 Ω

L

=

40 mA 12 25 Ω

L

OUT

=

I

40 mA to GND 90

L

DMax

OSC

=

=

(T

JMax−TA

2f

SW

)/θJA, where T

.

86 93

is the maximum junction temperature, TAis the

JMax

600 mW

V

%

%

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Test Circuit

FIGURE 1. LM2665 Test Circuit

Typical Performance Characteristics

LM2665

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(Circuit of Figure 1, V+=5V unless otherwise specified)

Supply Current vs
Supply Voltage

Output Source
Resistance vs Supply
Voltage

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Supply Current vs
Temperature

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Output Source
Resistance vs
Temperature

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Typical Performance Characteristics (Circuit of Figure 1, V+

specified) (Continued)

LM2665

=

5V unless otherwise

Output Voltage Drop
vs Load Current

Oscillator Frequency vs
Supply Voltage

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Efficiency vs
Load Current

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Oscillator Frequency vs
Temperature

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Shutdown Supply
Current vs
Temperature

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Connection Diagram

6-Lead SOT (M6)

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Actual Size

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Top View With Package Marking

Ordering Information

Order Number Package

Number

LM2665M6 MA06A SO4A (Note 9) Tape and Reel (1000 units/rail)

LM2665M6X MA06A SO4A (Note 9) Tape and Reel (3000 units/rail)

Note 9: The first letter ″S″ identifies the part as a switched capacitor converter. The next two numbers are the device number. The fourth letter ″A″ indicates the
grade. Only one grade is available. Larger quantity reels are available upon request.

Package

Marking

Supplied as

Pin Description

Pin Name Function

Voltage Doubler Voltage Split

1 V+ Power supply positive voltage input. Positive voltage output.
2 GND Power supply ground input Same as doubler
3 CAP− Connect this pin to the negative terminal of the

charge-pump capacitor

4 SD Shutdown control pin, tie this pin to ground in normal

operation.

5 OUT Positive voltage output. Power supply positive voltage

6 CAP+ Connect this pin to the positive terminal of the

charge-pump capacitor.

Same as doubler.

Same as doubler.

input
Same as doubler

LM2665

Circuit Description

The LM2665 contains four large CMOS switches which are
switched in a sequence to double the input supply voltage.
Energy transfer and storageare provided byexternal capaci­tors. Figure 2 illustrates the voltage conversion scheme.
When S
age V+. During this time interval, switches S
open. In the next time interval, S
same time, S
age V+ and the voltage across C
age when there is no load. The output voltage drop when a
load is added is determined by the parasitic resistance (R

s(on)

and the charge transfer loss between capacitors. Details will
be discussed in the following application information section.

and S4are closed, C1charges to the supply volt-

2

and S4are open; at the

and S3are closed, the sum of the input volt-

1

2

gives the 2V+ output volt-

1

and S3are

1

of the MOSFET switchesand the ESR ofthe capacitors)

-

d

FIGURE 2. Voltage Doubling Principle

Application Information

Positive Voltage Doubler

The main application of the LM2665 is to double the input
voltage. The range of the input supply voltage is 2.5V to

5.5V.
The output characteristics ofthis circuit canbe approximated

by an ideal voltage source in series with a resistance. The

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Application Information (Continued)

voltage source equals 2V+. The output resistance R

LM2665

function of the ON resistance of the internal MOSFET
switches, the oscillator frequency, the capacitance and ESR
of C

and C2. Since the switching current charging and dis-

1

charging C
effect of the ESR of the pumping capacitor C
plied by four in the output resistance. The output capacitor
C

2

equal to the output current, therefore, its ESR only counts
once in the output resistance. A good approximation of R
is:

is approximately twice as the output current, the

1

is charging and discharging at a current approximately

out

will be multi-

1

is a

out

Split V+ in Half

Another interesting application shown in the Basic Applica­tion Circuits is using the LM2665 as a precision voltage di­vider. . This circuit can be derived from the voltage doubler
by switching the input andoutput connections. In the voltage
divider,the input voltage applies across the OUTpin and the
GND pin (which arethe power rails forthe internal oscillator),
therefore no start-up diode is needed. Also, since the
off-voltage across each switchequals V
can be raised to +11V.

Shutdown Mode

A shutdown (SD) pin is available to disable the device and
reduce the quiescent current to 1 µA. In normal operating
mode, the SD pin is connected to ground.The device can be
brought into the shutdown mode by applying to the SD pin a

where RSWis the sum of the ON resistance of the internal
MOSFET switches shown in Figure 2.

The peak-to-peak output voltage ripple is determined by the
oscillator frequency, the capacitance and ESR of the output
capacitor C

:

2

voltage greater than 40%of the V+ pin voltage.

Capacitor Selection

As discussed in the

Positive Voltage Doubler

output resistance and ripple voltage are dependent on the
capacitance and ESR values of the external capacitors. The
output voltage dropis the loadcurrent times the output resis­tance, and the power efficiency is

High capacitance, low ESR capacitors can reduce both the
output resistance and the voltage ripple.

The Schottky diode D
nal oscillator circuit uses theOUT pin and the GNDpin. Volt­age across OUT andGND must be largerthan 1.8V to insure
the operation of the oscillator. During start-up, D
charge up the voltage at the OUT pin to start the oscillator;
also, it protects the device from turning-on its own parasitic
diode and potentially latching-up. Therefore, the Schottkydi­ode D

should have enough current carrying capability to

1

charge the output capacitor at start-up, as well as a low for­ward voltage to prevent the internal parasitic diode from

is only needed for start-up. The inter-

1

is used to

1

Where IQ(V+) is the quiescent power loss of the IC device,

2

and I

R

is the conversion loss associated with the switch

L

out

on-resistance, the two external capacitors and their ESRs.
The selection of capacitors is based on the specifications of

the dropout voltage (which equals I
age ripple, and the converter efficiency. Low ESR capacitors
(Table 1) are recommended to maximize efficiency, reduce
the output voltage drop and voltage ripple.

turning-on. A Schottky diode like 1N5817 can be used for
most applications. If the input voltage ramp is less than 10V/
ms, a smaller Schottky diode like MBR0520LT1 can be used
to reduce the circuit size.

Low ESR Capacitor Manufacturers

Manufacturer Phone Capacitor Type

Nichicon Corp. (708)-843-7500 PL & PF series, through-hole aluminum electrolytic
AVX Corp. (803)-448-9411 TPS series, surface-mount tantalum
Sprague (207)-324-4140 593D, 594D, 595D series, surface-mount tantalum
Sanyo (619)-661-6835 OS-CON series, through-hole aluminum electrolytic
Murata (800)-831-9172 Ceramic chip capacitors
Taiyo Yuden (800)-348-2496 Ceramic chip capacitors
Tokin (408)-432-8020 Ceramic chip capacitors

/2, the input voltage

in

), the output volt-

outRout

section, the

Other Applications

Paralleling Devices

Any number ofLM2665s can beparalleled to reduce the out­put resistance. Each device must have its own pumping ca­pacitor C
shown in Figure 3. The composite output resistance is:

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, while only one outputcapacitor C

1

is needed as

out

Other Applications (Continued)

FIGURE 3. Lowering Output Resistance by Paralleling Devices

Cascading Devices

Cascading the LM2665sis an easyway to produce a greater
voltage (A two-stage cascade circuit is shown in Figure 4).

The effective output resistance is equal to the weighted sum
of each individual device:

=

1.5R

R

out

out_1+Rout_2

LM2665

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Note that, the increasing of the number of cascading stages
is pracitically limited since it significantly reduces the effi­ciency, increases the output resistance and output voltage
ripple.

FIGURE 4. Increasing Output Voltage by Cascading Devices

Regulating V

OUT

It is possible to regulate the output of the LM2665 by use of
a low dropout regulator (such as LP2980-5.0). The whole
converter is depicted in Figure 5.

A different output voltage is possible by use of LP2980-3.3,
LP2980-3.0, or LP2980-adj.

>

2V

V

out_min+Vdrop_max

in_min

<

in_max

V

out_max+Vdrop_min

2V

FIGURE 5. Generate a Regulated +5V from +3V Input Voltage

Note that, the following conditions must be satisfied simulta­neously for worst case design:

(LP2980) + I

(LP2980) + I

out_maxxRout_max

out_minxRout_min

(LM2665)

(LM2665)

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Physical Dimensions inches (millimeters) unless otherwise noted

LM2665 Switched Capacitor Voltage Converter

6-Lead Small Outline Package (M6)

NS Package Number MA06A

For Order Numbers, refer to the table in the ″Ordering Information″ section of this document.

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