National Semiconductor LM2660, LM2661 Technical data

LM2660/LM2661 Switched Capacitor Voltage Converter

September 1999

General Description

The LM2660/LM2661 CMOS charge-pump voltage converter inverts a positive voltage in the range of 1.5V to 5.5V to thecorresponding negative voltage. The LM2660/LM2661 uses two low cost capacitors to provide 100 mA of output current without the cost, size, and EMI related to inductor based converters. With an operating current of only 120 µA and operating efficiency greater than 90%at most loads, the LM2660/LM2661 provides ideal performance for battery powered systems. The LM2660/LM2661 may also be used as a positive voltage doubler.

The oscillator frequency can be lowered by adding an external capacitor to the OSC pin.Also, the OSC pin may be used to drive the LM2660/LM2661 with an external clock. For LM2660, a frequency control (FC) pin selects the oscillator frequency of 10 kHz or 80 kHz. For LM2661, an external shutdown (SD) pin replaces the FC pin. The SD pin can be used to disable the device and reduce the quiescent current to 0.5 µA. The oscillator frequency for the LM2661 is 80 kHz.

Basic Application Circuits

Voltage Inverter

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Features

n Inverts or doubles input supply voltage n Narrow SO-8 and Mini SO-8 Package n 6.5Ω typical output resistance n 88%typical conversion efficiency at 100 mA n (LM2660) selectable oscillator frequency: 10 kHz/80 kHz n (LM2661) low current shutdown mode

Applications

n Laptop computers n Cellular phones n Medical instruments n Operational amplifier power supplies n Interface power supplies n Handheld instruments

Positive Voltage Doubler

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Splitting VINin Half

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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.

Supply Voltage (V+ to GND, or GND to OUT) 6V

LM2660/LM2661

LV (OUT − 0.3V) to (GND + 3V) FC, OSC The least negative of (OUT − 0.3V)

V+ and OUT Continuous Output Current 120 mA Output Short-Circuit Duration to GND (Note 2) 1 sec.

or (V+ − 6V) to (V+ + 0.3V)

Power Dissipation

25˚C) (Note 3) 735 mW 500 mW

Max (Note 3) 150˚C 150˚C

(Note 3) 170˚C/W 250˚C/W

Operating Junction Temperature

Range −40˚C to +85˚C Storage Temperature Range −65˚C to +150˚C Lead Temperature 300˚C

Package

MMM

(Soldering, 10 seconds) ESD Rating 2 kV

Electrical Characteristics

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

Symbol Parameter Condition Min Typ Max Units

V+ Supply Voltage R

Supply Current No Load FC=Open (LM2660) 0.12 0.5

Shutdown Supply Current (LM2661)

Shutdown Pin Input Voltage Shutdown Mode 2.0 (Note 5) (LM2661) Normal Operation 0.3

OUT

OSC

EFF

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: OUT may be shorted to GND for one second 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: In the test circuit, capacitors C age and efficiency.

Note 5: In doubling mode, when V Note 6: Specified output resistance includes internal switch resistance and capacitor ESR. Note 7: For LM2661, the oscillator frequency is 80 kHz. Note 8: The output switches operate at one half of the oscillator frequency, f

Output Current TA≤ +85˚C, OUT ≤ −4V 100

Output Resistance (Note 6) I

Oscillator Frequency (Note 7) OSC=Open FC=Open 5 10

Switching Frequency (Note 8) OSC=Open FC=Open 2.5 5

OSC Input Current FC=Open

Power Efficiency RL(1k) between V+and OUT 96 98

Voltage Conversion Efficiency No Load 99 99.96

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

out

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

150 µF. (Note 4)

1k Inverter, LV=Open 3.5 5.5

Inverter, LV=GND 1.5 5.5 V Doubler, LV=OUT 2.5 5.5

SD=Ground (LM2661)

1 3

0.5 2 µA

+85˚C, OUT ≤ −3.8V 100

100 mA T

≤ +85˚C 6.5 10

+85˚C 12

FC=V+ 40 80

FC=V+ 20 40

FC=V+

(500) between GND and OUT 92 96

100 mA to GND 88

DMax

and C2are 0.2Ω maximum ESR capacitors. Capacitors with higher ESR will increase output resistance, reduce output volt-

5V, minimum input high for shutdown equals V

OSC

JMax−TA

out

−3V.

)/θJA, where T

is the maximum junction temperature, TAis the

JMax

mALV=Open FC=V+ (LM2660) or

Ω

kHz

µA

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Test Circuits

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FIGURE 1. LM2660 and LM2661 Test Circuits

Typical Performance Characteristics

(Circuit of

Figure 1

LM2660/LM2661

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)

Supply Current vs Supply Voltage

Output Source Resistance vs Temperature

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Supply Current vs Oscillator Frequency

Efficiency vs Load Current

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Output Source Resistance vs Supply Voltage

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Output Voltage Drop vs Load Current

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Typical Performance Characteristics (Circuit of

Figure 1

) (Continued)

Efficiency vs Oscillator Frequency

LM2660/LM2661

Oscillator Frequency vs Supply Voltage (FC=V+)

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Output Voltage vs Oscillator Frequency

Oscillator Frequency vs Supply Voltage (FC=Open)

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Oscillator Frequency vs External Capacitance

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Oscillator Frequency vs Temperature (FC=V+)

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Oscillator Frequency vs Temperature (FC=Open)

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Shutdown Supply Current vs Temperature (LM2661 Only)

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