User's Guide
SNVA014C–November 1999–Revised April 2013
AN-1142 LM2661/3/4 Evaluation Board
1 Introduction
The LM2661, LM2663, and LM2664 are part of a family of CMOS charge-pump voltage converters
(Table 3). Each uses two small capacitors to achieve voltage inversion or voltage doubling without the
cost, size, and EMI of inductor based converters. Each device has a shutdown feature and the LM2661
and LM2663 also provide the ability to run the clock oscillator from an external source. You may also slow
the clock with an external capacitor on the LM2661 and LM2663. The small size and low profile of these
circuits makes them attractive for cellular phones, laptop computers, Op Amp power supplies, interface
power supplies, medical instruments, PDAs, and handheld instruments.
The LM2661 comes in SOIC-8 and VSSOP-8 packages and requires only an extra diode to double the
input voltage and provide up to 100mA of output current. It has a typical efficiency of 88% at 100mA
output and a typical output resistance of 6.5 Ω. This circuit typically draws only 500 nA of supply current in
shutdown mode and 120 µA when operating. The internal oscillator frequency is 80 kHz and the input
voltage range is +2.5 V to +5.5 V . The LM2661 is also capable of inverting an input voltage from +1.5 V
to +5.5 V when used in a different configuration.
The LM2663 comes in a SOIC-8 package and inverts the input voltage to provide up to 200mA of output
current. It has a typical efficiency of 86% at 200 mA output and a typical output resistance of 3.5 Ω. This
circuit draws only 10 µA of supply current in shutdown and 300 µA when operating. The internal oscillator
frequency is 150 kHz and the input voltage range is +1.5 V to +5.5 V . The LM2663 is also capable of
doubling an input voltage from +2.5 V to +5.5 V when used in a different configuration.
The LM2664 comes in a SOT23-6 package and inverts the input voltage to provide up to 40 mA of output
current. It has a typical efficiency of 91% at 40 mA output and a typical output resistance of 12 Ω. This
circuit draws only 1 µA of supply current in shutdown and 220 µA when on. The oscillator frequency is 160
kHz and the input voltage range is +1.8 V to +5.5 V (1)
Figure 1 contains the schematic for each circuit used.
A silkscreen for the evaluation board is shown in Figure 2.
A listing of the products used is shown in Table 1.
A listing of the switched capacitor family is given in Table 3.
(1) Maximum input voltage for any input on this evaluation board is +5.5 V.
All trademarks are the property of their respective owners.
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Discussion and Component Selection
Figure 1. Schematics
2 Discussion and Component Selection
On this evaluation board, the LM2661 is used in the doubling configuration. This configuration uses only
two capacitors and one diode. There is a manual shutdown jumper designated as J1 included. The
internal oscillator is used with a frequency of 80 kHz. In doubling mode, the oscillator frequency can only
be modified using an external capacitor and cannot be driven by an external clock. The Schottky diode D1
is needed only for start-up but should be able to handle the current required to charge the output capacitor
(I=C*dV/dt). An MBR0520LT1 20 V, 0.5A diode is used on this board. Capacitor selection is very
important. The capacitors chosen determine the output voltage ripple as well as the output resistance
(Equation 1 and Equation 2). From these equations it is easy to see how capacitor value and ESR help
determine the output resistance and output voltage ripple. For this circuit Taiyo-Yuden type 22µF ceramic
capacitors are used (Model EMK432BJ226MM). These capacitors are used because of their low ESR as
well as stable temperature and frequency characteristics. Therefore, they enhance the parts performance.
Tantalum and ceramic capacitors and other values may be used as well to fit different performance, size,
or cost requirements. Universal pads have been put on the evaluation board so that the capacitors can be
replaced with those of a different size.
The LM2663 is configured as an inverter on this board. A manual shutdown is included and designated J2.
The internal oscillator frequency of 150 kHz is used. The capacitor selection here is important as well
since the output resistance and voltage ripple equations are the same as they are for the LM2661
(Equation 1 and Equation 2). This circuit runs at a higher frequency than the LM2661 so smaller capacitor
values can be used. For this circuit Taiyo-Yuden type 10µF ceramic capacitors are used (Model
JMK316BJ106ML-T). Once again the low ESR and stable characteristics of these capacitors are the
reasons they were chosen. Other types and sizes of capacitors may be used here as well for different
performance, size, or cost requirements.
The LM2664 is also used as an inverter on this board. A manual shutdown designated as J3 is included.
The LM2664 does not have an adjustable frequency; it is fixed at 160 kHz. This circuit has the same
equations for output resistance and output voltage ripple as the previous two circuits and the capacitor
selection is once again important (Equation 1 and Equation 2). Taiyo Yuden multi-layer ceramic chip 3.3
µF capacitors are used for this circuit (Model LMK316BJ335ML-T). These capacitors are chosen for their
low ESR (measured ≊25 mΩ) and small (1206) case size. They show the high performance of the
LM2664 as well as the small size for the complete circuit. The output voltage ripple was measured to be
less than 75mV peak to peak with a 40 mA load. Again other types and sizes of capacitors may be used
for different performance and/or size requirements.
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Discussion and Component Selection
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In these equations C2is always the output capacitor of the circuit.
(1)
where RSW is the sum of the ON resistance of the internal switches. RSW is typically 1.4 Ωfor the LM2661,
0.9 Ωfor the LM2663, and 4 Ωfor the LM2664.
(2)
Figure 2. Silkscreen
4AN-1142 LM2661/3/4 Evaluation Board SNVA014C–November 1999–Revised April 2013
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Discussion and Component Selection
Table 1. Components List
Designator Part Type Manufacturer and Model No Footprint Description
U1 LM2661 Texas Instruments VSSOP-8 Charge-pump voltage converter
D1 Diode Motorola (MBR0520LT1) SOD123 20 V, 0.5A Start-up diode
C1 22µF Taiyo-Yuden 1206 Low ESR charge-pump capacitor,
(EMK432BJ226MM) MLCC
C2 22µF Taiyo-Yuden 1206 Low ESR charge-pump capacitor,
(EMK432BJ226MM) MLCC
U2 LM2663 Texas Instruments SO-8 Charge-pump voltage converter
C3 10µF Taiyo-Yuden 1206 Low ESR charge-pump capacitor,
(JMK316BJ106ML-T) MLCC
C4 10µF Taiyo-Yuden 1206 Low ESR charge-pump capacitor,
(JMK316BJ106ML-T) MLCC
U3 LM2664 Texas Instruments SOT23-6 Charge-pump voltage converter
C5 3.3µF Taiyo Yuden 1206 Low ESR charge-pump capacitor,
(LMK316BJ335ML-T) MLCC
C6 3.3µF Taiyo Yuden 1206 Low ESR charge-pump capacitor,
(LMK316BJ335ML-T) MLCC
VIN1, VIN2, Headers (36 posts Amphenol (842-800-272-015) 0.1" spacing Connectors for input voltage, output
VIN3, J1, J2, per strip) Newark stock # 87F6830 voltage, and ON/OFF jumpers (2/3
J3, J4 strip used, 22 posts used, 19 actual
pins used per board)
J1, J2, J3 Shunts Circuit Assembly Corp. (CA-02SJC-B) Shunts for ON/OFF jumpers, shorts 2
Newark stock # 90F9279 pins, 3 shunts used per board
Table 2. Contact Information
Texas Instruments www.ti.com 1-800-272-9959
Motorola www.mot.com 1-800-521-6274
Taiyo Yuden www.T-Yuden.com 1-800-348-2496
Newark www.Newark.com 1-800-298-3133
Table 3. Switched Capacitor Family
ROIOUT VIN Shut Freq. Freq.
Product Function (Ω) (mA) Range fOSC kHz IQ(µA) down Control Sync Package
LM2660 −VIN or 2 VIN 6.5 100 1.5 to 5.5 10/80 120/400 No Yes Yes VSSOP-8,
SOIC-8
LM2661 −VIN or 2 VIN 6.5 100 1.5 to 5.5 80 1000 Yes No Yes VSSOP-8,
SOIC-8
LM2662 −VIN or 2 VIN 3.5 200 1.5 to 5.5 20/150 300/1300 No Yes Yes SOIC-8
LM2663 −VIN or 2 VIN 3.5 200 1.5 to 5.5 150 1300 Yes No Yes SOIC-8
LM2664 −VIN 12 40 1.8 to 5.5 160 220 Yes No No SOT23-6
LM2665 2 VIN 12 40 1.8 to 5.5 160 550 Yes No No SOT23-6
LM3350 3/2 VIN or 2/3 VIN 4.2/1.8 50 1.5 to 5.5 1600 3750 Yes No No VSSOP-8
LM3351 3/2 VIN or 2/3 VIN 4.2/1.8 50 1.5 to 5.5 400 1110 Yes No No VSSOP-8
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