LMC7660IM

LMC7660 www.ti.com SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 LMC7660 Switched Capacitor Voltage Converter Check for Samples: LMC7660 FEATURES DESCRIPTION • The LMC7660 is a CMOS voltage converter capable of converting a positive voltage in the range of +1.5V to +10V to the corresponding negative voltage of −1.5V to −10V. The 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. 1 2 • • • • • • • Operation Over Full Temperature and Voltage Range without an External Diode Low Supply Current, 200 μA 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 The LMC7660 uses its built-in oscillator to switch 4 power MOS switches and charge two inexpensive electrolytic capacitors. Block Diagram Pin Configuration 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 1997–2013, Texas Instruments Incorporated LMC7660 SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ABSOLUTE MAXIMUM RATINGS (1) (2) Supply Voltage 10.5V −0.3V to (V+ + 0.3V) for V+ < 5.5V Input Voltage on Pin 6, 7 (3) + (V − 5.5V) to (V+ + 0.3V) for V+ > 5.5V Current into Pin 6 (3) 20 μA Output Short Circuit Duration (V+ ≤ 5.5V) Power Dissipation Continuous (4) PDIP Package 1.4W SOIC Package TJ Max 0.6W (4) 150°C θJA (4) PDIP Package 90°C/W SOIC Package 160°C/W −65°C ≤ T ≤ 150°C Storage Temp. Range Lead Temperature (Soldering, 5 sec.) ESD Tolerance (1) (2) (3) (4) (5) 260°C (5) ± 2000V 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 (1) under Electrical Characteristics for conditions. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. Connecting any input terminal to voltages greater than V+ 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. For operation at elevated temperature, these devices must be derated based on a thermal resistance of θja and Tj max, Tj = TA + θja PD. The test circuit consists of the human body model of 100 pF in series with 1500Ω. ELECTRICAL CHARACTERISTICS (1) Symbol Parameter Conditions Typ LMC7660IN/ LMC7660IM Limit Is V+H Supply Current Supply Voltage Range High V+L (1) (2) (3) 2 (3) RL = ∞ 120 RL = 10 kΩ, Pin 6 Open 3 to 10 Voltage Efficiency ≥ 90% Supply Voltage RL = 10 kΩ, Pin 6 to Gnd. Range Low Voltage Efficiency ≥ 90% (2) Units Limits 200 μA 400 max 3 to 10 V 3 to 10 1.5 to 3.5 1.5 to 3.5 V 1.5 to 3.5 Boldface numbers apply at temperature extremes. All other numbers apply at TA = 25°C, V+ = 5V, Cosc = 0, and apply for the LMC7660 unless otherwise specified. Test circuit is shown in Figure 1 . Limits at room temperature are specified and 100% production tested. Limits in boldface are specified over the operating temperature range (but not 100% tested), and are not used to calculate outgoing quality levels. The LMC7660 can operate without an external diode over the full temperature and voltage range. The LMC7660 can also be used with the external diode Dx, when replacing previous 7660 designs. Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 LMC7660 www.ti.com SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 ELECTRICAL CHARACTERISTICS(1) (continued) Symbol Parameter Conditions Typ LMC7660IN/ LMC7660IM Limit Rout Output Source IL = 20 mA 55 V = 2V, IL = 3 mA 110 Resistance Pin 6 Short to Gnd. Fosc Oscillator (2) Units Limits 100 Ω 120 max 200 Ω 300 max 10 kHz Frequency Peff Power Efficiency RL = 5 kΩ Vo Voltage Conversion RL = ∞ eff 97 99.9 Efficiency Iosc Oscillator Sink or Pin 7 = Gnd. or V+ 95 % 90 min 97 % 95 min 3 μA Source Current Figure 1. LMC7660 Test Circuit Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 3 LMC7660 SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS 4 OSC Freq. vs OSC Capacitance Vout vs Iout @ V+ = 2V Figure 2. Figure 3. Vout vs Iout @ V+ = 5V Supply Current & Power Efficiency vs Load Current (V+ = 2V) Figure 4. Figure 5. Supply Current & Power Efficiency vs Load Current (V+ = 5V) Output Source Resistiance as a Function of Temperature Figure 6. Figure 7. Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 LMC7660 www.ti.com SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unloaded Oscillator Frequency as a Function of Temperature Output R vs Supply Voltage Figure 8. Figure 9. Peff vs OSC Freq. @ V+ = 5V Figure 10. Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 5 LMC7660 SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 www.ti.com APPLICATION INFORMATION CIRCUIT DESCRIPTION The LMC7660 contains four large CMOS switches which are switched in a sequence to provide supply inversion Vout = −Vin. Energy transfer and storage are provided by two inexpensive electrolytic capacitors. Figure 11 shows how the LMC7660 can be used to generate −V+ from V+. When switches S1 and S3 are closed, Cp charges to the supply voltage V+. During this time interval, switches S2 and S4 are open. After Cp charges to V+, S1 and S3 are opened, S2 and S4 are then closed. By connecting S2 to ground, Cp develops a voltage −V+/2 on Cr. After a number of cycles Cr will be pumped to exactly −V+. This transfer will be exact assuming no load on Cr, and no loss in the switches. In the circuit of Figure 11, 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 p− wells of S3 and S4 never become forward biased with respect to either their sources or drains. A substrate logic circuit specifies that these p− wells are always held at the proper voltage. Under all conditions S4 p− well must be at the lowest potential in the circuit. To switch off S4, a level translator generates VGS4 = 0V, and this is accomplished by biasing the level translator from the S4 p− well. An internal RC oscillator and ÷ 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+ = 6.5V. Low voltage operation can be improved if the LV pin is shorted to ground for V+ ≤ 3.5V. For V+ ≥ 3.5V, the LV pin must be left open to prevent damage to the part. 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. The 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: (1) 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: (2) PRECAUTIONS 1. 2. 3. 4. Do not exceed the maximum supply voltage or junction temperature. Do not short pin 6 (LV terminal) to ground for supply voltages greater than 3.5V. Do not short circuit the output to V+. 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 TI LMC7660 has been designed to solve the inherent latch problem. The LCM7660 can operate over the entire supply voltage and temperature range without the need for an output diode. When replacing existing designs, the LMC7660 can be operated with diode Dx. 6 Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 LMC7660 www.ti.com SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 Figure 11. Idealized Voltage Converter TYPICAL APPLICATIONS CHANGING OSCILLATOR FREQUENCY It is possible to dramatically reduce the quiescent operating current of the 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 12). As shown in the Typical Performance Curves the supply current can be lowered to the 10 μA range. This low current drain can be extremely useful when used in μPower 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. SYNCHRONIZING TO AN EXTERNAL CLOCK Figure 13 shows an 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 ÷2 circuit in the 7660, so the pumping frequency will be ½ the external clock frequency. Figure 12. Reduce Supply Current by Lowering Oscillator Frequency Figure 13. Synchronizing to an External Clock Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 7 LMC7660 SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 www.ti.com LOWERING OUTPUT IMPEDANCE Paralleling two or more 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 14. The composite output resistance is: (3) INCREASING OUTPUT VOLTAGE Stacking the LMC7660s is an easy way to produce a greater negative voltage. It should be noted that the input current required for each stage is twice the load current on that stage as shown in Figure 15. 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 −15V from +5V by connecting the second 7660's pin 8 to +5V instead of ground as shown in Figure 16. Note that the second 7660 sees a full 20V and the input supply should not be increased beyond +5V. Figure 14. Lowering Output Resistance by Paralleling Devices Figure 15. Higher Voltage by Cascade Figure 16. Getting −15V from +5V 8 Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 LMC7660 www.ti.com SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 SPLIT V+ IN HALF Figure 17 is one of the more interesting applications for the LMC7660. The circuit can be used as a precision voltage divider (for very light loads), alternately it is used to generate a ½ supply point in battery applications. In the ½ cycle when S1 and S3 are closed, the supply voltage divides across the capacitors in a conventional way proportional to their value. In the ½ 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+/2, across Cp and Cr. In this application all devices are only V+/2, and the supply voltage can be raised to 20V giving exactly 10V at Vout. GETTING UP … AND DOWN The LMC7660 can also be used as a positive voltage multiplier. This application, shown in Figure 18, requires 2 additional diodes. During the first ½ cycle S2 charges Cp1 through D1; D2 is reverse biased. In the next ½ cycle S2 is open and S1 is closed. Since Cp1 is charged to V+ − VD1 and is referenced to V+ through S1, the junction of D1 and D2 is at V+ + (V+ −VD1). 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 19. In the ½ cycle that D1 is charging Cp1, Cp2 is connected from ground to −Vout 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+, while Cp2 is refreshed from V+. Figure 17. Split V+ in Half Figure 18. Positive Voltage Multiplier Figure 19. Combined Negative Converter and Positive Multiplier Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 9 LMC7660 SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 www.ti.com THERMOMETER SPANS 180°C Using the combined negative and positive multiplier of Figure 20 with an LM35 it is possible to make a μPower thermometer that spans a 180°C temperature range. The LM35 temperature sensor has an output sensitivity of 10 mV/°C, while drawing only 50 μA of quiescent current. In order for the LM35 to measure negative temperatures, a pull down to a negative voltage is required. Figure 20 shows a thermometer circuit for measuring temperatures from −55°C to +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 −VOUT It is possible to regulate the output of the LMC7660 and still maintain μPower performance. This is done by enclosing the LMC7660 in a loop with a LP2951. The circuit of Figure 21 will regulate Vout to −5V for IL = 10 mA, and Vin = 6V. For Vin > 7V, the output stays in regulation up to IL = 25 mA. The error flag on pin 5 of the LP2951 sets low when the regulated output at pin 4 drops by about 5%. The LP2951 can be shutdown by taking pin 3 high; the LMC7660 can be shutdown by shorting pin 7 and pin 8. The LP2951 can be reconfigured to an adjustable type regulator, which means the LMC7660 can give a regulated output from −2.0V to −10V dependent on the resistor ratios R1 and R2, as shown in Figure 22, Vref = 1.235V: (4) *For lower voltage operation, use Schottky rectifiers Figure 20. μPower Thermometer Spans 180°C, and Pulls Only 150 μA Figure 21. Regulated −5V with 200 μA Standby Current 10 Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 LMC7660 www.ti.com SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 Vref = 1.235V *Low voltage operation Figure 22. LMC7660 and LP2951 Make a Negative Adjustable Regulator Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 11 LMC7660 SNOSBZ9C – APRIL 1997 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision B (April 2013) to Revision C • 12 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 11 Submit Documentation Feedback Copyright © 1997–2013, Texas Instruments Incorporated Product Folder Links: LMC7660 PACKAGE OPTION ADDENDUM www.ti.com 26-Aug-2022 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) Samples (4/5) (6) LMC7660IM NRND SOIC D 8 95 Non-RoHS & Green Call TI Level-1-235C-UNLIM LMC76 60IM LMC7660IM/NOPB ACTIVE SOIC D 8 95 RoHS & Green SN Level-1-260C-UNLIM LMC7660IMX NRND SOIC D 8 2500 Non-RoHS & Green Call TI Level-1-235C-UNLIM LMC7660IMX/NOPB ACTIVE SOIC D 8 2500 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 LMC76 60IM Samples LMC7660IN/NOPB ACTIVE PDIP P 8 40 RoHS & Green NIPDAU Level-1-NA-UNLIM -40 to 85 LMC 7660IN Samples -40 to 85 LMC76 60IM LMC76 60IM (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of