LMC7660 LMC7660MJ LMC7660IN LMC7660IM C1996 RRD-B30M66 1500X LCM7660 LP2951 - Datasheet Archive

 

General Description Features The LMC7660 is a CMOS voltage converter capable of converting a positive voltage in the range of a 1

 

LMC7660 LMC7660 Switched Capacitor Voltage Converter General Description Features The LMC7660 LMC7660 is a CMOS voltage converter capable of converting a positive voltage in the range of a 1 5V to a 10V to the corresponding negative voltage of b1 5V to b10V The LMC7660 LMC7660 is a pin-for-pin replacement for the industry-standard 7660 The converter features operation over full temperature and voltage range without need for an external diode low quiescent current and high power efficiency The LMC7660 LMC7660 uses its built-in oscillator to switch 4 power MOS switches and charge two inexpensive electrolytic capacitors Y Y Y Y Y Y Y Y Y Operation over full temperature and voltage range without an external diode Low supply current 200 mA max Pin-for-pin replacement for the 7660 Wide operating range 1 5V to 10V 97% Voltage Conversion Efficiency 95% Power Conversion Efficiency Easy to use only 2 external components Extended temperature range Narrow SO-8 Package Block Diagram TL H 9136 ­ 1 Pin Configuration Ordering Information LMC7660 LMC7660 LMC7660MJ LMC7660MJ b55 C s TA s a 125 C LMC7660IN LMC7660IN b40 C s TA s a 85 C LMC7660IM LMC7660IM b40 C s TA s a 85 C TL H 9136 ­ 2 C1996 C1996 National Semiconductor Corporation TL H 9136 RRD-B30M66 RRD-B30M66 Printed in U S A LMC7660 LMC7660 Switched Capacitor Voltage Converter June 1996 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 Input Voltage on Pin 6 7 (Note 2) Power Dissipation (Note 3) Tj Max (Note 3) 10 5V b 0 3V to (V a a 0 3V) ija (Note 3) Storage Temp Range Lead Temp (Soldering 5 sec) ESD Tolerance (Note 8) for V a k 5 5V (V a b 5 5V) to (V a a 0 3V) for V a l 5 5V Current into Pin 6 (Note 2) Output Short Circuit Duration (V a s 5 5V) 20 mA J 0 9W Package N 1 4W M 0 8W 150 C 150 C 150 C 140 C W 90 C W 160 C W b 65 C s T s 150 C 260 C 260 C 260 C g 2000V g 2000V Continuous Electrical Characteristics (Note 4) LMC7660MJ LMC7660MJ Symbol Parameter LMC7660IN LMC7660IN LMC7660IM LMC7660IM Tested Limit (Note 5) Tested Limit (Note 5) Design Limit (Note 6) 120 Conditions 200 400 200 400 mA max Typ Units Limits Is Supply Current RL e % VaH Supply Voltage Range High (Note 7) RL e 10 kX Pin 6 Open Voltage Efficiency t 90% 3 to 10 3 to 10 3 to 10 3 to 10 V VaL Supply Voltage Range Low RL e 10 kX Pin 6 to Gnd Voltage Efficiency t 90% 1 5 to 3 5 1 5 to 3 5 1 5 to 3 5 1 5 to 3 5 V Rout Output Source Resistance IL e 20 mA 55 100 150 100 120 X max V e 2V IL e 3 mA Pin 6 Short to Gnd 110 200 300 200 300 X max 97 Fosc Oscillator Frequency Peff Power Efficiency RL e 5 kX Vo eff Voltage Conversion Efficiency RL e % Iosc Oscillator Sink or Source Current Pin 7 e Gnd or V a 10 99 9 kHz 95 90 95 90 % min 97 95 97 95 % min 3 mA Note 1 Absolute Maximum ratings indicate limits beyond which damage to the device may occur DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions See Note 4 for conditions Note 2 Connecting any input terminal to voltages greater than V a or less than ground may cause destructive latchup It is recommended that no inputs from sources operating from external supplies be applied prior to ``power-up'' of the LMC7660 LMC7660 Note 3 For operation at elevated temperature these devices must be derated based on a thermal resistance of ija and Tj max Tj e TA a ija PD Note 4 Boldface numbers apply at temperature extremes All other numbers apply at TA e 25 C V a e 5V Cosc e 0 and apply for the LMC7660 LMC7660 unless otherwise specified Test circuit is shown in Figure 1 Note 5 Guaranteed and 100% production tested Note 6 Guaranteed over the operating temperature range (but not 100% tested) These limits are not used to calculate outgoing quality levels Note 7 The LMC7660 LMC7660 can operate without an external diode over the full temperature and voltage range The LMC7660 LMC7660 can also be used with the external diode Dx when replacing previous 7660 designs Note 8 The test circuit consists of the human body model of 100 pF in series with 1500X 1500X http www national com 2 TL H 9136 ­ 5 FIGURE 1 LMC7660 LMC7660 Test Circuit Typical Performance Characteristics OSC Freq vs OSC Capacitance Vout vs Iout Supply Current Power Efficiency vs Load Current (V a e 2V) Supply Current Power Efficiency vs Load Current (V a e 5V) Output Source Resistance as a Function of Temperature Unloaded Oscillator Frequency as a Function of Temperature Output R vs Supply Voltage Peff vs OSC Freq V a e 2V Vout vs Iout V a e 5V V a e 5V TL H 9136 ­ 4 3 http www national com The LMC7660 LMC7660 closely approaches 1 and 2 above By using a large pump capacitor Cp the charge removed while supplying the reservoir capacitor is small compared to Cp's total charge Small removed charge means small changes in the pump capacitor voltage and thus small energy loss and high efficiency The energy loss by Cp is E e Cp (V12 b V22) CIRCUIT DESCRIPTION The LMC7660 LMC7660 contains four large CMOS switches which are switched in a sequence to provide supply inversion Vout e b Vin Energy transfer and storage are provided by two inexpensive electrolytic capacitors Figure 2 shows how the LMC7660 LMC7660 can be used to generate bV a from V a When switches S1 and S3 are closed Cp charges to the supply voltage V a During this time interval switches S2 and S4 are open After Cp charges to V a S1 and S3 are opened S2 and S4 are then closed By connecting S2 to ground Cp develops a voltage bV a 2 on Cr After a number of cycles Cr will be pumped to exactly bV a This transfer will be exact assuming no load on Cr and no loss in the switches In the circuit of Figure 2 S1 is a P-channel device and S2 S3 and S4 are N-channel devices Because the output is biased below ground it is important that the pb wells of S3 and S4 never become forward biased with respect to either their sources or drains A substrate logic circuit guarantees that these pb wells are always held at the proper voltage Under all conditions S4 pb well must be at the lowest potential in the circuit To switch off S4 a level translator generates VGS4 e 0V and this is accomplished by biasing the level translator from the S4 p b well An internal RC oscillator and d 2 circuit provide timing signals to the level translator The built-in regulator biases the oscillator and divider to reduce power dissipation on high supply voltage The regulator becomes active at about V a e 6 5V Low voltage operation can be improved if the LV pin is shorted to ground for V a s 3 5V For V a t 3 5V the LV pin must be left open to prevent damage to the part By using a large reservoir capacitor the output ripple can be reduced to an acceptable level For example if the load current is 5 mA and the accepted ripple is 200 mV then the reservoir capacitor can omit approximately be calculated from Is e Cr V E Cr c ripple p-p 4 Fosc dv dt Cr e 0 5 mA e 10 mF 0 5V ms PRECAUTIONS 1) Do not exceed the maximum supply voltage or junction temperature 2) Do not short pin 6 (LV terminal) to ground for supply voltages greater than 3 5V 3) Do not short circuit the output to V a 4) External electrolytic capacitors Cr and Cp should have their polarities connected as shown in Figure 1 REPLACING PREVIOUS 7660 DESIGNS To prevent destructive latchup previous 7660 designs require a diode in series with the output when operated at elevated temperature or supply voltage Although this prevented the latchup problem of these designs it lowered the available output voltage and increased the output series resistance The National LMC7660 LMC7660 has been designed to solve the inherent latch problem The LCM7660 LCM7660 can operate over the POWER EFFICIENCY AND RIPPLE It is theoretically possible to approach 100% efficiency if the following conditions are met 1) The drive circuitry consumes little power 2) The power switches are matched and have low Ron 3) The impedance of the reservoir and pump capacitors are negligibly small at the pumping frequency TL H 9136 ­ 6 FIGURE 2 Idealized Voltage Converter http www national com 4 used in mPower and battery back-up equipment It must be understood that the lower operating frequency and supply current cause an increased impedance of Cr and Cp The increased impedance due to a lower switching rate can be offset by raising Cr and Cp until ripple and load current requirements are met entire supply voltage and temperature range without the need for an output diode When replacing existing designs the LMC7660 LMC7660 can be operated with diode Dx Typical Applications Changing Oscillator Frequency It is possible to dramatically reduce the quiescent operating current of the LMC7660 LMC7660 by lowering the oscillator frequency The oscillator frequency can be lowered from a nominal 10 kHz to several hundred hertz by adding a slow-down capacitor Cosc (Figure 3) As shown in the Typical Performance Curves the supply current can be lowered to the 10 mA range This low current drain can be extremely useful when Synchronizing to an External Clock Figure 4 shows an LMC7660 LMC7660 synchronized to an external clock The CMOS gate overrides the internal oscillator when it is necessary to switch faster or reduce power supply interference The external clock still passes through the d 2 circuit in the 7660 so the pumping frequency will be the external clock frequency TL H 9136 ­ 7 FIGURE 3 Reduce Supply Current by Lowering Oscillator Frequency TL H 9136 ­ 8 FIGURE 4 Synchronizing to an External Clock 5 http www national com Typical Applications (Continued) current required for each stage is twice the load current on that stage as shown in Figure 6A The effective output resistance is approximately the sum of the individual Rout values and so only a few levels of multiplication can be used It is possible to generate b15V from a 5V by connecting the second 7660's pin 8 to a 5V instead of ground as shown in Figure 6B Note that the second 7660 sees a full 20V and the input supply should not be increased beyond a 5V Lowering Output Impedance Paralleling two or more LMC7660 LMC7660's lowers output impedance Each device must have it's own pumping capacitor Cp but the reservoir capacitor Cr is shared as depicted in Figure 5 The composite output resistance is Rout of one LMC7660 LMC7660 Rout e Number of devices Increasing Output Voltage Stacking the LMC7660s is an easy way to produce a greater negative voltage It should be noted that the input TL H 9136 ­ 9 FIGURE 5 Lowering Output Resistance by Paralleling Devices TL H 9136 ­ 10 FIGURE 6A Higher Voltage by Cascade TL H 9136 ­ 11 FIGURE 6B Getting b15V from a 5V http www national com 6 Typical Applications (Continued) Split V a In Half Getting Up Figure 7 is one of the more interesting applications for the LMC7660 LMC7660 The circuit can be used as a precision voltage divider (for very light loads) alternately it is used to generate a supply point in battery applications In the cycle when S1 and S3 are closed the supply voltage divides across the capacitors in a conventional way proportional to their value In the cycle when S2 and S4 are closed the capacitors switch from a series connection to a parallel connection This forces the capacitors to have the same voltage the charge redistributes to maintain precisely V a 2 across Cp and Cr In this application all devices are only V a 2 and the supply voltage can be raised to 20V giving exactly 10V at Vout The LMC7660 LMC7660 can also be used as a positive voltage multiplier This application shown in Figure 8 requires 2 additional diodes During the first cycle S2 charges Cp1 through D1 D2 is reverse biased In the next cycle S2 is open and S1 is closed Since Cp1 is charged to V a b VD1 and is referenced to V a through S1 the junction of D1 and D2 is at V a a (V a bVD1) D1 is reverse biased in this interval This application uses only two of the four switches in the 7660 The other two switches can be put to use in performing a negative conversion at the same time as shown in Figure 9 In the cycle that D1 is charging Cp1 Cp2 is connected from ground to bVout via S2 and S4 and Cr2 is storing Cp2's charge In the interval that S1 and S3 are closed Cp1 pumps the junction of D1 and D2 above V a while Cp2 is refreshed from V a and Down TL H 9136 ­ 12 FIGURE 7 Split V a in Half TL H 9136 ­ 13 FIGURE 8 Positive Voltage Multiplier 7 http www national com Typical Applications (Continued) TL H 9136 ­ 14 FIGURE 9 Combined Negative Converter and Positive Multiplier the LMC7660 LMC7660 in a loop with a LP2951 LP2951 The circuit of Figure 11 will regulate Vout to b5V for IL e 10 mA and Vin e 6V For Vin l 7V the output stays in regulation up to IL e 25 mA The error flag on pin 5 of the LP2951 LP2951 sets low when the regulated output at pin 4 drops by about 5% The LP2951 LP2951 can be shutdown by taking pin 3 high the LMC7660 LMC7660 can be shutdown by shorting pin 7 and pin 8 The LP2951 LP2951 can be reconfigured to an adjustable type regulator which means the LMC7660 LMC7660 can give a regulated output from b2 0V to b10V dependent on the resistor ratios R1 and R2 as shown in Figure 12 Vref e 1 235V R1 Vout e Vref 1 a R2 Thermometer Spans 180 C Using the combined negative and positive multiplier of Figure 10 with an LM35 it is possible to make a mPower thermometer that spans a 180 C temperature range The LM35 temperature sensor has an output sensitivity of 10 mV C while drawing only 50 mA of quiescent current In order for the LM35 to measure negative temperatures a pull down to a negative voltage is required Figure 10 shows a thermometer circuit for measuring temperatures from b55 C to a 125 C and requiring only two 1 5V cells End of battery life can be extended by replacing the up converter diodes with Schottky's Regulating bVout It is possible to regulate the output of the LMC7660 LMC7660 and still maintain mPower performance This is done by enclosing For lower voltage operation use Schottky rectifiers J TL H 9136 ­ 15 FIGURE 10 mPower Thermometer Spans 180 C and Pulls Only 150 mA http www national com 8 Typical Applications (Continued) TL H 9136 ­ 16 FIGURE 11 Regulated b5V with 200 mA Standby Current Vout e Vref 1 Vref e 1 235V a R1 R2 J TL H 9136 ­ 17 Low voltage operation FIGURE 12 LMC7660 LMC7660 and LP2951 LP2951 Make a Negative Adjustable Regulator 9 http www national com http www national com 10 Physical Dimensions inches (millimeters) unless otherwise noted Ceramic Dual-In-Line Package (J) Order Number LMC7660MJ LMC7660MJ NS Package Number J08A 11 http www national com LMC7660 LMC7660 Switched Capacitor Voltage Converter Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Molded Dual-In-Line Package (N) Order Number LMC7660IN LMC7660IN NS Package Number N08E LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or systems which (a) are intended for surgical implant into the body or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user National Semiconductor Corporation 1111 West Bardin Road Arlington TX 76017 Tel 1(800) 272-9959 Fax 1(800) 737-7018 http www national com 2 A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness National Semiconductor Europe Fax a49 (0) 180-530 85 86 Email europe support nsc com Deutsch Tel a49 (0) 180-530 85 85 English Tel a49 (0) 180-532 78 32 Fran ais Tel a49 (0) 180-532 93 58 Italiano Tel a49 (0) 180-534 16 80 National Semiconductor Hong Kong Ltd 13th Floor Straight Block Ocean Centre 5 Canton Rd Tsimshatsui Kowloon Hong Kong Tel (852) 2737-1600 Fax (852) 2736-9960 National Semiconductor Japan Ltd Tel 81-043-299-2308 Fax 81-043-299-2408 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