CMOS Monolithic Voltage Converter

Transcription

1 9-9; Rev. ; 9/9 CMOS Monolithic Voltage Converter General escription The monolithic, charge-pump voltage inverter converts a +.V to +.V input to a corresponding -.V to -.V output. Using only two low-cost capacitors, the charge pump s ma output replaces switching regulators, eliminating inductors and their associated cost, size, and EMI. Greater than 9% efficiency over most of its load-current range combined with a typical operating current of only µa provides ideal performance for both battery-powered and boardlevel voltage conversion applications. The can also double the output voltage of an input power supply or battery, providing +9.V at ma from a +V input. A frequency control (FC) pin selects either khz typ or khz typ (khz min) operation to optimize capacitor size and quiescent current. The oscillator frequency can also be adjusted with an external capacitor or driven with an external clock. The is a pincompatible, high-current upgrade of the ICL7. The is available in both -pin IP and smalloutline packages in commercial, extended, and military temperature ranges. For ma applications, consider the / pin-compatible devices (also available in ultra-small µ packages). Applications Laptop Computers Medical Instruments Interface Power Supplies Hand-Held Instruments Operational-Amplifier Power Supplies Pin Configuration TOP VIEW FC CAP+ GN CAP- CAP- 7 OSC LV OUT Features Small Capacitors.V Typ Loss at ma Load Low µa Operating Current.Ω Typ Output Impedance Guaranteed R OUT < Ω for C = C = µf Pin-Compatible High-Current ICL7 Upgrade Inverts or oubles Input Supply Voltage Selectable Oscillator Frequency: khz/khz % Typ Conversion Efficiency at ma (I L to GN) Ordering Information PART TEMP. RANGE PIN-PACKAGE CPA C to +7 C Plastic IP CSA C to +7 C SO C/ C to +7 C ice* EPA - C to + C Plastic IP ESA - C to + C SO MJA - C to + C CERIP *Contact factory for dice specifications. Typical Operating Circuits C µf to µf C µf to µf +V IN.V TO.V FC CAP+ OSC GN LV CAP- GN 7 OUT VOLTAGE INVERTER FC CAP+ OSC LV OUT 7 +V IN.V TO.V INVERTE NEGATIVE VOLTAGE OUTPUT C µf to µf OUBLE POSITIVE VOLTAGE OUTPUT C µf to µf IP/SO POSITIVE VOLTAGE OUBLER Maxim Integrated Products For free samples & the latest literature: or phone --99-

2 ABSOLUTE IMUM RATINGS Supply Voltage ( to GN, or GN to OUT)...+V LV Input Voltage...(OUT -.V) to ( +.V) FC and OSC Input Voltages...The least negative of (OUT -.V) or ( - V) to ( +.V) OUT and Continuous Output Current...mA Output Short-Circuit uration to GN (Note )...sec Continuous Power issipation (T A = +7 C) Plastic IP (derate 9.9mW/ C above + 7 C)...77mW SO (derate.mw/ C above +7 C)...7mW CERIP (derate.mw/ C above +7 C)...mW Operating Temperature Ranges C... C to +7 C E...- C to + C MJA...- C to + C Storage Temperature Range... - to + C Lead Temperature (soldering, sec)... + C Note : OUT may be shorted to GN for sec without damage, but shorting OUT to may damage the device and should be avoided. Also, for temperatures above + C, OUT must not be shorted to GN or, even instantaneously, or device damage may result. Stresses beyond those listed under Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS ( = V, C = C = µf, test circuit of Figure, FC = open, T A = T to T, unless otherwise noted.) (Note ) PARAMETER CONITIONS TYP UNITS Inverter, LV = open.. Operating Supply Voltage R L = kω Inverter, LV = GN.. V oubler, LV = OUT.. Supply Current No load FC = open, LV = open.. FC =, LV = open ma Output Current T A + C, OUT more negative than -V T A > + C, OUT more negative than -.V ma T A + C, C = C = µf, FC = (Note ) Output Resistance (Note ) I L = ma T A + C, C = C = µf.. Ω T A + C Oscillator Frequency FC = open FC = khz OSC Input Current FC = open ± FC = ± µa R L = kω connected between and OUT 9 9 Power Efficiency R L = Ω connected between OUT and GN 9 9 % IL = ma to GN Voltage-Conversion Efficiency No load Note : In the test circuit, capacitors C and C are µf,.ω maximum ESR, aluminum electrolytics. Capacitors with higher ESR may reduce output voltage and efficiency. See Capacitor Selection section. Note : Specified output resistance is a combination of internal switch resistance and capacitor ESR. See Capacitor Selection section. Note : The ESR of C = C.Ω. Guaranteed by correlation, not production tested. %

3 Typical Operating Characteristics All curves are generated using the test circuit of Figure with =V, LV = GN, FC = open, and T A = + C, unless otherwise noted. The charge-pump frequency is one-half the oscillator frequency. Test results are also valid for doubler mode with GN = +V, LV = OUT, and OUT = V, unless otherwise noted; however, the input voltage is restricted to +.V to +.V. C FC CAP+ OSC GN LV 7 I S (+V ) CAP- OUT R L C I L V OUT Figure. Test Circuit SUPPLY CURRENT vs. SUPPLY VOLTAGE - SUPPLY CURRENT vs. OSCILLATOR FREQUENCY - -. OUTPUT VOLTAGE AN EFFICIENCY vs. LOA CURRENT, = V -A SUPPLY CURRENT (µa) LV = OUT LV = OPEN LV = GN SUPPLY CURRENT (ma). OUTPUT VOLTAGE (V) ICL7 ICL7 EFF. V OUT 9 7 EFFICIENCY (%) SUPPLY VOLTAGE (V).. -. LOA CURRENT (ma) EFFICIENCY (%) 9 7 EFFICIENCY vs. LOA CURRENT =.V =.V =.V =.V =.V LOA CURRENT (ma) - OUTPUT VOLTAGE ROP FROM SUPPLY (V) OUTPUT VOLTAGE ROP vs. LOA CURRENT =.V =.V 7 9 LOA CURRENT (ma) =.V =.V =.V - OUTPUT VOLTAGE (V) OUTPUT VOLTAGE vs. OSCILLATOR FREQUENCY I LOA = ma I LOA = ma I LOA = ma. -

4 Typical Operating Characteristics (continued) EFFICIENCY (%) EFFICIENCY vs. OSCILLATOR FREQUENCY I LOA = ma I LOA = ma I LOA = ma.. OSCILLATOR FREQUENCY vs. EXTERNAL CAPACITANCE FC = FC = OPEN OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE LV = GN FC =, OSC = OPEN FC, OSC = OPEN LV LV = = OPEN OPEN SUPPLY.. VOLTAGE. (V).... SUPPLY VOLTAGE (V) OSCILLATOR FREQUENCY vs. TEMPERATURE FC =, OSC = OPEN, RL = Ω -7 - OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE LV = GN FC = OPEN, OSC = OPEN LV = OPEN..... SUPPLY VOLTAGE (V) OSCILLATOR FREQUENCY vs. TEMPERATURE FC = OPEN, OSC = OPEN R L = Ω -A -. CAPACITANCE (pf) TEMPERATURE ( C) TEMPERATURE ( C) OUTPUT SOURCE RESISTANCE (Ω) OUTPUT SOURCE RESISTANCE vs. SUPPLY VOLTAGE SUPPLY VOLTAGE (V) - OUTPUT SOURCE RESISTANCE (Ω) OUTPUT SOURCE RESISTANCE vs. TEMPERATURE C, C = µf ALUUM ELECTROLYTIC CAPACITORS R L = Ω =.V TEMPERATURE ( C) =.V =.V - OUTPUT SOURCE RESISTANCE (Ω) OUTPUT SOURCE RESISTANCE vs. TEMPERATURE C, C = µf OS-CON CAPACITORS R L = Ω =.V =.V TEMPERATURE ( C) =.V -

5 CURRENT (ma) CURRENT (ma) OUTPUT CURRENT vs. CAPACITANCE: V IN = +.V, V OUT = -V FC = OSC = OPEN CAPACITANCE (µf) OUTPUT CURRENT vs. CAPACITANCE: V IN = +.V, V OUT = -.7V FC = OSC = OPEN CAPACITANCE (µf) CHART - CHART - Pin escription CURRENT (ma) CURRENT (ma) OUTPUT CURRENT vs. CAPACITANCE: V IN = +.V, V OUT = -.V FC = OSC = OPEN CAPACITANCE (µf) OUTPUT CURRENT vs. CAPACITANCE: V IN = +.V, V OUT = -.V FC = OSC = OPEN CAPACITANCE (µf) CHART - CHART - PIN NAME NAME INVERTER FUNCTION OUBLER FC Frequency Control for internal oscillator, FC = open, f OSC = khz typ; FC =, f OSC = khz typ (khz min), FC has no effect when OSC pin is driven externally. Same as Inverter CAP+ Charge-Pump Capacitor, Positive Terminal Same as Inverter GN Power-Supply Ground Input Power-Supply Positive Voltage Input CAP- Charge-Pump Capacitor, Negative Terminal Same as Inverter OUT Output, Negative Voltage Power-Supply Ground Input LV Low-Voltage Operation Input. Tie LV to GN when input voltage is less than V. Above V, LV may be connected to GN or left open; when overdriving OSC, LV must be connected to GN. LV must be tied to OUT for all input voltages. 7 OSC Oscillator Control Input. OSC is connected to an internal pf capacitor. An external capacitor can be added to slow the oscillator. Take care to minimize stray capacitance. An external oscillator may also be connected to overdrive OSC. Same as Inverter; however, do not overdrive OSC in voltage-doubling mode. Power-Supply Positive Voltage Input Positive Voltage Output

6 etailed escription The capacitive charge-pump circuit either inverts or doubles the input voltage (see Typical Operating Circuits). For highest performance, low effective series resistance (ESR) capacitors should be used. See Capacitor Selection section for more details. When using the inverting mode with a supply voltage less than V, LV must be connected to GN. This bypasses the internal regulator circuitry and provides best performance in low-voltage applications. When using the inverter mode with a supply voltage above V, LV may be connected to GN or left open. The part is typically operated with LV grounded, but since LV may be left open, the substitution of the for the ICL7 is simplified. LV must be grounded when overdriving OSC (see Changing Oscillator Frequency section). Connect LV to OUT (for any supply voltage) when using the doubling mode. Applications Information Negative Voltage Converter The most common application of the is as a charge-pump voltage inverter. The operating circuit uses only two external capacitors, C and C (see Typical Operating Circuits). Even though its output is not actively regulated, the is very insensitive to load current changes. A typical output source resistance of.ω means that with an input of +V the output voltage is -V under light load, and decreases only to -.V with a load of ma. Output source resistance vs. temperature and supply voltage are shown in the Typical Operating Characteristics graphs. Output ripple voltage is calculated by noting the output current supplied is solely from capacitor C during Table. Single-Output Charge Pumps one-half of the charge-pump cycle. This introduces a peak-to-peak ripple of: V RIPPLE = I OUT + I OUT (ESR C ) (f PUMP ) (C) For a nominal f PUMP of khz (one-half the nominal khz oscillator frequency) and C = µf with an ESR of.ω, ripple is approximately 9mV with a ma load current. If C is raised to 9µF, the ripple drops to mv. Positive Voltage oubler The operates in the voltage-doubling mode as shown in the Typical Operating Circuit. The no-load output is x V IN. Other Switched-Capacitor Converters Please refer to Table, which shows Maxim s chargepump offerings. Changing Oscillator Frequency Four modes control the s clock frequency, as listed below: FC OSC Oscillator Frequency Open Open khz FC = Open khz Open or External See Typical Operating FC = Capacitor Characteristics Open External External Clock Frequency Clock When FC and OSC are unconnected (open), the oscillator runs at khz typically. When FC is connected to, the charge and discharge current at OSC changes from.µa to.µa, thus increasing the oscillator 9 ICL7 ICL7 Package SOT - SOT - Op. Current (typ, ma) Output Ω (typ) Pump Rate (khz).. SO-, µ. at khz,. at khz,. at khz SO-, µ. at khz,. at khz,. at khz SO-, µ...,,,,, Input (V). to.. to.. to.. to.. to.. to SO-. at khz, at khz SO-.. to SO-, µ.. to

7 frequency eight times. In the third mode, the oscillator frequency is lowered by connecting a capacitor between OSC and GN. FC can still multiply the frequency by eight times in this mode, but for a lower range of frequencies (see Typical Operating Characteristics). In the inverter mode, OSC may also be overdriven by an external clock source that swings within mv of and GN. Any standard CMOS logic output is suitable for driving OSC. When OSC is overdriven, FC has no effect. Also, LV must be grounded when overdriving OSC. o not overdrive OSC in voltage-doubling mode. Note: In all modes, the frequency of the signal appearing at CAP+ and CAP- is one-half that of the oscillator. Also, an undesirable effect of lowering the oscillator frequency is that the effective output resistance of the charge pump increases. This can be compensated by increasing the value of the charge-pump capacitors (see Capacitor Selection section and Typical Operating Characteristics). In some applications, the khz output ripple frequency may be low enough to interfere with other circuitry. If desired, the oscillator frequency can then be increased through use of the FC pin or an external oscillator as described above. The output ripple frequency is onehalf the selected oscillator frequency. Increasing the clock frequency increases the s quiescent current, but also allows smaller capacitance values to be used for C and C. Capacitor Selection Three factors (in addition to load current) affect the output voltage drop from its ideal value: ) output resistance ) Pump (C) and reservoir (C) capacitor ESRs ) C and C capacitance The voltage drop caused by output resistance is the load current times the output resistance. Similarly, the loss in C is the load current times C s ESR. The loss in C, however, is larger because it handles currents that are greater than the load current during charge-pump operation. The voltage drop due to C is therefore about four times C s ESR multiplied by the load current. Consequently, a low (or high) ESR capacitor has a much greater impact on performance for C than for C. Generally, as the pump frequency of the increases, the capacitance values required to maintain comparable ripple and output resistance diminish proportionately. The curves of Figure show the total circuit TOTAL OUTPUT SOURCE RESISTANCE (Ω) khz khz khz khz khz khz khz CAPACITANCE (µf) output resistance for various capacitor values (the pump and reservoir capacitors values are equal) and oscillator frequencies. These curves assume.ω capacitor ESR and a.ω output resistance, which is why the flat portion of the curve shows a.ω (R O + (ESR C ) + ESR C ) effective output resistance. Note: R O =.Ω is used, rather than the typical.ω, because the typical specification includes the effect of the ESRs of the capacitors in the test circuit. In addition to the curves in Figure, four bar graphs in the Typical Operating Characteristics show output current for capacitances ranging from.µf to µf. Output current is plotted for inputs of.v (V-%) and.v (.V-%), and allow for % and % output droop with each input voltage. As can be seen from the graphs, the.ω series resistance limits increases in output current vs. capacitance for values much above 7µF. Larger values may still be useful, however, to reduce ripple. To reduce the output ripple caused by the charge pump, increase the reservoir capacitor C and/or reduce its ESR. Also, the reservoir capacitor must have low ESR if filtering high-frequency noise at the output is important. Not all manufacturers guarantee capacitor ESR in the range required by the. In general, capacitor ESR is inversely proportional to physical size, so larger capacitance values and higher voltage ratings tend to reduce ESR. -fig ESR =.Ω FOR BOTH C AN C OUTPUT SOURCE RESISTANCE ASSUME TO BE.Ω Figure. Total Output Source Resistance vs. C and C Capacitance (C = C) 7

8 The following is a list of manufacturers who provide low-esr electrolytic capacitors: Manufacturer/ Series Phone Fax Comments AVX TPS Series () 9-9 () - AVX TAG Series () 9-9 () - Matsuo 7 Series (7) 99-9 (7) 9-9 Sprague 9 Series Sanyo MV-GX Series Sanyo CV-GX Series Nichicon PL Series United Chemi-Con (Marcon) () -9 () - (9) - (9) - (9) - (9) - (7) -7 (7) -79 Low-ESR tantalum SMT Low-cost tantalum SMT Low-cost tantalum SMT Aluminum electrolytic thru-hole Aluminum electrolytic SMT Aluminum electrolytic thru-hole Low-ESR tantalum SMT (7) 9- (7) 9-97 Ceramic SMT TK (7) 9-7 (7) 9- Ceramic SMT Cascading evices To produce larger negative multiplication of the initial supply voltage, the may be cascaded as shown in Figure. The resulting output resistance is approximately equal to the sum of the individual R OUT values. The output voltage, where n is an integer representing the number of devices cascaded, is defined by V OUT = -n (V IN ). Paralleling evices Paralleling multiple s reduces the output resistance. As illustrated in Figure, each device requires its own pump capacitor C, but the reservoir capacitor C serves all devices. The value of C should be increased by a factor of n, where n is the number of devices. Figure shows the equation for calculating output resistance. R OUT = R OUT (of ) n (NUMBER OF EVICES) +V IN C "" +V IN Cn "n" V OUT C "" Cn "n" R L Cn C V OUT = -nv IN C Figure. Cascading s to Increase Output Voltage Figure. Paralleling s to Reduce Output Resistance

9 Combined Positive Supply Multiplication and Negative Voltage Conversion This dual function is illustrated in Figure. In this circuit, capacitors C and C perform the pump and reservoir functions respectively for generation of the negative voltage. Capacitors C and C are respectively pump and reservoir for the multiplied positive voltage. This circuit configuration, however, leads to higher source impedances of the generated supplies. This is due to the finite impedance of the common charge-pump driver. +V IN µf M V LITHIUM BATTERY URACELL LA M OPEN-RAIN LOW-BATTERY OUTPUT LBI V/mA IN OUT µf 7 7 LBO k µf SET GN SHN M k C, = N C V OUT = -V IN NOTE: ALL µf CAPACITORS ARE C, AVAILABLE FROM IM. Figure. generates a +V regulated output from a V lithium battery and operates for hours with a ma load. C C V OUT = (V IN ) - (V F ) - (V F ) Figure. Combined Positive Multiplier and Negative Converter 9

10 Chip Topography FC CAP+ GN OSC LV." (.mm) CAP- OUT.7" (.mm) TRANSISTOR COUNT = 9 SUBSTRATE CONNECTE TO.

11 CMOS Monolithic Voltage Converter Package Information IM A A A A B B C E E e ea eb L INCHES MILLIMETERS Plastic IP PLASTIC UAL-IN-LINE PACKAGE (. in.) IM PKG. P P P P P N INCHES MILLIMETERS PINS C A A E E ea eb A B B - A L e -A IM A A B C E e H L INCHES MILLIMETERS -A Narrow SO SMALL-OUTLINE PACKAGE (. in.) IM INCHES MILLIMETERS PINS.7. L - H E e A A C.mm.in. B

12 Package Information (continued) A L Q e B B L E E - C IM A B B C E E e L L Q S S INCHES MILLIMETERS S S CERIP CERAMIC UAL-IN-LINE PACKAGE (. in.) IM PINS INCHES MILLIMETERS A Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, San Gabriel rive, Sunnyvale, CA 9 () Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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