September 1999
LM2660/LM2661
Switched Capacitor Voltage Converter
General Description
The LM2660/LM2661 CMOS charge-pump voltage converter inverts a positive voltage in the range of 1.5V to 5.5V to the corresponding 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.
Features
nInverts or doubles input supply voltage
nNarrow SO-8 and Mini SO-8 Package
n6.5Ω typical output resistance
n88% typical conversion efficiency at 100 mA
n(LM2660) selectable oscillator frequency: 10 kHz/80 kHz
n(LM2661) low current shutdown mode
Applications
nLaptop computers
nCellular phones
nMedical instruments
nOperational amplifier power supplies
nInterface power supplies
nHandheld instruments
Basic Application Circuits
Voltage Inverter |
Positive Voltage Doubler |
DS012911-3
DS012911-4
Splitting VIN in Half
DS012911-26
Converter Voltage Capacitor Switched LM2660/LM2661
© 1999 National Semiconductor Corporation |
DS012911 |
www.national.com |
LM2660/LM2661
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 |
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LV |
(OUT − 0.3V) to (GND + 3V) |
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FC, OSC |
The least negative of (OUT − 0.3V) |
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or (V+ − 6V) to (V+ + 0.3V) |
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V+ and OUT Continuous Output Current |
120 mA |
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Output Short-Circuit Duration to GND (Note 2) |
1 sec. |
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Package |
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M |
MM |
Power Dissipation |
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(TA = 25ÊC) (Note 3) |
735 mW |
500 mW |
TJ Max (Note 3) |
150ÊC |
150ÊC |
θJA (Note 3) |
170ÊC/W |
250ÊC/W |
Operating Junction |
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Temperature |
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Range |
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−40ÊC to +85ÊC |
Storage Temperature Range |
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−65ÊC to +150ÊC |
Lead Temperature |
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300ÊC |
(Soldering, 10 seconds) |
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ESD Rating |
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2 kV |
Electrical Characteristics
Limits in standard typeface are for TJ = 25ÊC, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: V+ = 5V, FC = Open, C1 = C2 = 150 µF. (Note 4)
Symbol |
Parameter |
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Condition |
Min |
Typ |
Max |
Units |
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V+ |
Supply Voltage |
RL = 1k |
Inverter, LV = Open |
3.5 |
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5.5 |
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Inverter, LV = GND |
1.5 |
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5.5 |
V |
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Doubler, LV = OUT |
2.5 |
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5.5 |
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IQ |
Supply Current |
No Load |
FC = Open (LM2660) |
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0.12 |
0.5 |
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LV = Open |
FC = V+ (LM2660) or |
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1 |
3 |
mA |
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SD = Ground (LM2661) |
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ISD |
Shutdown Supply Current |
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0.5 |
2 |
µA |
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(LM2661) |
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VSD |
Shutdown Pin Input Voltage |
Shutdown Mode |
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2.0 |
(Note 5) |
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V |
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(LM2661) |
Normal Operation |
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0.3 |
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IL |
Output Current |
TA ≤ +85ÊC, OUT ≤ −4V |
100 |
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mA |
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TA > +85ÊC, OUT ≤ −3.8V |
100 |
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ROUT |
Output Resistance (Note 6) |
IL = 100 mA |
TA ≤ +85ÊC |
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6.5 |
10 |
Ω |
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TA > +85ÊC |
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12 |
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fOSC |
Oscillator Frequency (Note 7) |
OSC = Open |
FC = Open |
5 |
10 |
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kHz |
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FC = V+ |
40 |
80 |
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fSW |
Switching Frequency (Note 8) |
OSC = Open |
FC = Open |
2.5 |
5 |
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kHz |
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FC = V+ |
20 |
40 |
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IOSC |
OSC Input Current |
FC = Open |
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±2 |
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µA |
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FC = V+ |
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±16 |
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PEFF |
Power Efficiency |
RL (1k) between V+ and OUT |
96 |
98 |
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RL (500) between GND and OUT |
92 |
96 |
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% |
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IL = 100 mA to GND |
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88 |
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VOEFF |
Voltage Conversion Efficiency |
No Load |
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99 |
99.96 |
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% |
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 85ÊC, 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 PDMax = (TJMax − T A)/θJA, where TJMax is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction-to-ambient thermal resistance of the specified package.
Note 4: In the test circuit, capacitors C1 and C2 are 0.2Ω maximum ESR capacitors. Capacitors with higher ESR will increase output resistance, reduce output voltage and efficiency.
Note 5: In doubling mode, when Vout > 5V, minimum input high for shutdown equals Vout − 3V.
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, fOSC = 2fSW.
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2 |
Test Circuits
DS012911-5
DS012911-6
FIGURE 1. LM2660 and LM2661 Test Circuits
Typical Performance Characteristics (Circuit of Figure 1)
Supply Current vs |
Supply Current vs |
Output Source |
Supply Voltage |
Oscillator Frequency |
Resistance vs Supply |
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Voltage |
DS012911-7
DS012911-8
DS012911-9
Output Source |
Efficiency vs Load |
Output Voltage Drop |
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Resistance vs |
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Current |
vs Load Current |
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Temperature |
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DS012911-11 |
DS012911-12 |
DS012911-10
LM2660/LM2661
3 |
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LM2660/LM2661
Typical Performance Characteristics (Circuit of Figure 1) (Continued)
Efficiency vs |
Output Voltage vs |
Oscillator Frequency |
Oscillator Frequency |
Oscillator Frequency |
vs External |
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Capacitance |
DS012911-13 |
DS012911-14 |
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DS012911-15 |
Oscillator Frequency |
Oscillator Frequency |
Oscillator Frequency |
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vs Supply Voltage |
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vs Supply Voltage |
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vs Temperature |
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(FC = V+) |
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(FC = Open) |
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(FC = V+) |
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DS012911-16 |
DS012911-17 |
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DS012911-18 |
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Oscillator Frequency |
Shutdown Supply |
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vs Temperature |
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Current vs |
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(FC = Open) |
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Temperature |
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(LM2661 Only) |
DS012911-19
DS012911-20
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