19-3293, Rev. 0, 3/91 General Description The MAX660 monolithic, charge-pump voltage inverter converts a +1.5V to +5.5V input to a corresponding -1.5V to -5.5V output. Using only two low-cost capacitors, the charge pump's 100mA output replaces switching regulators, eliminating inductors and their associated cost, size, and EMI. Greater than 90% efficiency over most of its load-current range combined with a typical operating current of only 200uA provides ideal pertfor- mance for both battery-powered and board-level voltage conversion applications. The MAX660 can also double the output voltage of an input power supply or battery, providing +9.35V at 100mA from a +5V input A Frequency Control (FC) pin selects either 10kHz or 45kHz 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 MAX660 is a pin-compatible high-current upgrade of the ICL7660. The MAX660 is available in both 8-pin DIP and small outline packages in commercial, extended, and military temperature ranges. Applications Laptop Computers Medical Instruments Interface Power Supplies Handheld Instruments MA AASV CMOS Monolithic Voltage Converter Features @ 0.65V Typ Loss at 100mA Load @ 6.5 Typ Output Impedance @ Pin-Compatible High-Current ICL7660 Upgrade Inverts or Doubles input Supply Voltage @ Selectable Oscillator Frequency: 10kHz/45kHz @ 88% Typ Conversion Efficiency at 100mA (IL to GND) @ 200A Operating Current Ordering Information PART TEMP.RANGE _PIN-PACKAGE MAX660CPA OC to +70C 8 Plastic DIP | MAX660CSA OC to +70C 8S0 MAX660C/D OC to +70C Dice* MAX660EPA -40C to +85C Plastic DIP | MAX660ESA -40C to +85C 8S0 MAX660MJA 55C to + 125C 8 CERDIP * Contact factory for dice specifications. Typical Operating Circuits Operational-Amplifier Power Supplies VN 15VT05 5V 1 8 TFC ve Pin Configuration I caps osc} + 3] AAAXLAA |. 150yF > ~] GND Wke INVERTED " t 4 MAX660 + NEGATIVE TOP VIEW = *F cap- out? VOLTAGE 150 pF VOLTAGE INVERTER SF 4e - 1N5817 Fe [4] 3 | Ve ~ - CAPs [2 | 7 | osc DOUBLED | AMAXIM | 1 8 POSITIVE sno [3] MAX660 [e) WV HFC Ve VOLTAGE cap: [4] is} Our C12 ase? 5) 150uF | CAP 7s 150ue <3] Maxum |. +Vin --# GND MAX660 LV DIP/SO asvTossv =| y 5 LT cap- OUT POSITIVE VOLTAGE DOUBLER = MAAXIsVI Maxim Integrated Products 4-117 JAA AISI is a registered trademark of Maxim Integrated Products : o o> SMAX660 CMOS Monolithic Voltage Converter ABSOLUTE MAXIMUM RATINGS Operating Temperature Ranges: Supply Voltage (V+ to GND, or GND to OUT)... 2.0... +6V MAX660C 8 eee cece ce eee 0C to +70C LV Input Voltage ..............0.. OUT - 0.3V to V+ + 0.3V MAX660E 40C to +85C FC and OSC Input Voltages .......... (the least negative of Te a ncn ga 10 485) MAX660MJA 00. eee -68C to +125C OUT - 0.3V or V+ - GV) to V+ + 0.3V Storage Temperature 65C to +160C OUT and V+ Continuous Output Current......00..... 120mA eg Output Short-Circuit Duration to GND (Note 1) ....... 10 sec. Lead Temperature (Soldering, 10 sec.) ............. +300C Continuous Tota! Power Dissipation (Ta = +70C) Plastic DIP (derate 6.9mW/C above +70C) ....... 552mW SO (derate 5.88mMW/C above +70C) ............ A71imw CERDIP (derate 8.OmW/C above +70C) ......... 640mW 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+ = 5V, C1, C2 = 150pF; test circuit of Figure 1; FC = open; Ta = TMIN to TMA, unless otherwise noted.) (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS Inverter, LV = open 3 6.6 Operating Supply Voltage Ri = 1kQ Inverter, LV = GND 15 .5 Vv Doubler, LV = OUT 2.5 5.5 Supply Current No Load FC = open 02 05 mA FC = V+ 1 3 Ta < +85C, OUT more negative than -4V 100 Output Current 5 - mA Ta > +85C, OUT more negative than -3.8V 100 Output Resistance (Note 3) IL = 100mA Tas +85C 8.5 10 Q Ta > +85C 12 Oscillator Frequency FC = open 10 kHz FC = V+ 45 OSC Input Current Fo = open #1 BA FC =V+ +5 RL = 1kQ connected between V+ and OUT 96 98 Power Efficiency Ri = 500Q connected between OUT and GND 92 96 % IL = 100mA to GND 88 Voltage Conversion Efficiency No Load 99 99.96 % Note 1: [n inverting mode, OUT may be shorted to GND for 10 sec. without damage, but shorting OUT to V+ may damage the device and should be avoided. in doubler mode, shorts of V+ to OUT can be tolerated indefinitely, but the Schottky diode current rating could be exceeded. {n doubler mode, V+ may be shorted to GND for 10 sec. without damage. Note 2: In the test circuit, capacitors C1 and C2 are 150uF, 0.20 maximum ESR, aluminum electrolytics (Maxim part # MAXC001). Capacitors with higher ESR may reduce output voltage and efficiency. Note 3: Specified output resistance is a combination of internai switch resistance and capacitor ESR. See Capacitor Selection section. 4-118 MAXAIsvICMOS Monolithic Voltage Converter Typical Operating Characteristics (All curves are generated using the test circuit of Figure 1 with V+ = 5V, LV = GND, FC = open, and Ta = +25C, unless otherwise noted. The charge-pump frequency is one-haif the oscillator frequency. Test results are also valid for doubler mode with GND = +5V, LV = OUT, and OUT = OV, unless otherwise noted; however, the input voltage is restricted to +2.5V to +5.5V. Ve AAAXIUAA (+5) MAX660 IY Vout 4 C2 [> 150uF Figure 1. MAX660 Test Circuit SUPPLY CURRENT SUPPLY CURRENT OUTPUT VOLTAGE AND EFFICIENCY vs. SUPPLY VOLTAGE vs. OSCILLATOR FREQUENCY vs. LOAD CURRENT, V+ = 5V DOUBLER MODE LV =QUT LV = OPEN SUPPLY CURRENT (1A) SUPPLY CURRENT (A) LV= MAX660 > = ~ oO OUTPUT VOLTAGE (V) EFFICIENCY (%) > a MAX660 0 60 1520 2530 35 40 45 50 55 0.01 0.1 1 10 400 0 20 40 60 8 100 SUPPLY VOLTAGE (V) OSCILLATOR FREQUENCY {kHz} LOAD CURRENT (mA) OUTPUT VOLTAGE DROP OUTPUT VOLTAGE EFFICIENCY vs. LOAD CURRENT s vs. LOAD CURRENT vs. OSCILLATOR FREQUENCY = 5.0 Va = 5.5V 3 ft = NU | S loan = 10mA > 45 Lh | a T z 5 = joan =1ma_ 4 = a 3 / | a 3 = 40 ILoAD = BOmA S = gS | = Ves & & = > Ww ee V+ 25V 2 B35 S ' V+= 1.5V = V+ =5 5V | 2 3.0 h : 0 2 4 6 80 100 5 0 2 8640)~SiBOstiSC 010204 1 2 4 10 20 40 100 LOAD CURRENT (mA) LOAD CURRENT (mA) OSCILLATOR FREQUENCY {kH2) MAXI SI 4-119 O99XVUNMAX660 CMOS Monolithic Voltage Converter Typical Operating Characteristics (continued) EFFICIENCY vs. OUTPUT SOURCE RESISTANCE OUTPUT SOURCE RESISTANCE OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE vs. TEMPERATURE a =1 = Qa Sg g 3 3 z = wo wa J a zB 5 we = 40 a 2 3 V+= 3VDC Ss = 3 iz 3 B 8 5 5 = = 6 ILoaD = 1A 3 2 V+ = 5VDC 60 0 - 4 010204 1 2 4 10 20 40 100 0510 15 20 25 30 3540 45 50 55 -60 -40-20 0 20 40 60 80 100 120140 OSCILLATOR FREQUENCY (kHz) SUPPLY VOLTAGE () TEMPERATURE (C) OSCILLATOR FREQUENCY OSCILLATOR FREQUENCY _ OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE vs. SUPPLY VOLTAGE 7 vs. TEMPERATURE lv LY GROUNDED Lr _ = 4 rat a" zg z LV OPEN 2 = LV OPEN 3 LT 1 =, oS s 6 = 5 30-- z= s 3 5 g = & 5 f FC = OPEN, OSC - OPEN = 29 = fod = = 2 s FC= V+, OSC = OPEN = 4 s = Ss 3 Z 10 3 B 8 0 0 0 10 15 20 2540 35 4045 50 55 10 15 20 25 3035 40 45 50 $5 -60 40-20 0 20 40 60 80 100 120 140 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE () TEMPERATURE ('C) OSCILLATOR FREQUENCY OSCILLATOR FREQUENCY vs. TEMPERATURE vs. EXTERNAL CAPACITANCE 100 g Zo >= > ao oOo = = a a 2 S = = & FC = V4, OSC = = i e 3 So 3 5 FC = OPEN 3 8 0 0.0% 80-40-20 0 20 40 60 80 100 120 140 12 51020 100 500 2000 10000 TEMPERATURE (C) CAPACITANCE (pF) 4-120 IUAXISVICMOS Monolithic Voltage Converter Pin Description FUNCTION PIN | NAME INVERTER DOUBLER Frequency Control for internal oscillator. FC = open, 1 FC fosc = 10kHz typ; FC = V+, fosc = 45kHz typ: FC has no Same as Inverter effect when OSC pin is driven externally. 2 CAP+ | Charge-Pump Capacitor, Positive Terminal Same as Inverter 3 GND Power-Supply Ground Input Power-Supply Positive Voltage !nput 4 CAP- | Charge-Pump Capacitor, Negative Terminal Same as Inverter 5 OUT Output, Negative Voltage Power-Supply Ground Input Low-Voltage Operation input. Tie LV to GND when input voltage 6 LV is less than 3V. Above 3V, LV may be connected to GND or Ie! LV must be tied to OUT for all input voltages. open; when overdriving OSC, LV must be connected to GND. Oscillator Control Input. OSC is connected to an internal 15pF . : 7 osc | capacitor. An extemal capacitor can be added to slow the oscil- ware Bee eck Cee cate logic lator. Care must be taken to minimize stray capacitance. An ex-| Souisics mode @ ontact faclory fo aCe. i ternal oscillator may also be connected to overdrive OSC. : act lactory Tor details. 8 V+ Power-Supply Positive Voltage Input Positive Voltage Output Detailed Description The MAX660 capacitive charge-pump circuit either in- verts or doubles the input voltage. Two external capacitors are needed in the voltage inverting mode, while two capacitors and one diode are needed for the voltage doubling mode (see Typical Operating Circuits). For highest performance, low effective series resistance (ESR) capacitors should be used. See Capacitor Selec- tion section for more details. When using the inverting mode with a supply voltage less than 3V, LV must be connected to GND. This bypasses the internal regulator circuitry and provides best perfor- mance in low-voltage applications. When using the in- verter mode with a supply voltage above 3V, LV may be connected to GND or left open. The part is typically operated with LV grounded, but since LV may be left open, the substitution of the MAX660 for the ICL7660 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 doubler mode. Application Hints Negative Voltage Converter The most common application of the MAX660 is as a charge-pump voltage inverter. The operating circuit MAAI/VI uses only two external capacitors, C1 and C2 (see Typical Operating Circuits). In most applications these are low- cost, low-ESR, 150uF electrolytic capacitors (Refer to Capacitor Selection section). Even though its output is not actively regulated, the MAX660 is very insensitive to load current changes. A typical output source resistance of 6.5Q means that with an input of +5V the output voltage is -5V under light load, and decreases only to -4.35V with a load of 100mA. 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 C2 during one- half of the charge-pump cycle. This introduces a peak- to-peak ripple of: IOUT VRIPPLE = 2(fPUMP) (C2) + lout (ESRc2) For a nominal fpump of S5kHz (one-half the nominal 10kHz oscillator frequency) and C2 = 150uF with an ESR of 0.22, ripple is approximately 9OmV with a 100mA load current. If C2 is raised to 390pF, the ripple drops to 45mvV. 4-121 O99XVWMAX660 CMOS Monolithic Voltage Converter Positive Voltage Doubler The MAX660 operates in the voltage-doubling mode as shown in the Typical Operating Circuit. The external Schottky (1N5817) diode is for start-up only. The no-load output is 2 x VIN and is not reduced by the diode forward drop. Changing Oscillator Frequency Four modes control the MAX660s clock frequency, as listed below: FC osc Oscillator Frequency Open Open 10kHz FC = V+ Open 45kHz Open or See Typical Operating FC = V+ External Capacitor Characteristics Open External Ciock External Clock Frequency When FC and OSC are unconnected (open), the oscil- lator runs at 10kHz typically. When FC is connected to V+, the charge and discharge current at OSC changes from 1.1pA to 5p, thus increasing the oscillator frequen- cy 4.5 times. In the third mode, the oscillator frequency is lowered by connecting a capacitor between OSC and GND. FC can still multiply the frequency by 4.5 times in this mode, but for a lower range of frequencies (see Typical Operating Characterisitics). In the inverter mode, OSC may also be overdriven by an external clock source that swings within 100mV of V+ and GND. 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. Stand- ard logic levels cannot overdrive OSC in voltage doubler mode. Contact factory for details. Note: |n 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 Selec- tion section and Typical Operating Characteristics). insome applications, the 5kHz output ripple frequency may be low enough to interfere with other circuitry. !f 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 one-half the selected oscil- lator frequency. Increasing the clock frequency increases the MAX660's quiescent current, but also allows smaller capacitance values to be used for C1 and C2. Capacitor Selection Three factors (in addition to load current) affect the MAX660 output voltage drop from its ideal value: 4-122 1) MAX660 output resistance 2) Pump (C1) and reservoir (C2) capacitor ESRs 3) C1 and C2 capacitance The voltage drop caused by MAX660 output resistance is the load current times the output resistance. Similarly, the loss in C2 is the load current times C2's ESR. The loss in C1, however, is larger because it handles currents that are greater than the load current during charge- pump operation. The voltage drop due to C1 is therefore about 4 times C1s ESR times the load current. Conse- quently, a low (or high) ESR capacitor has much greater impact on performance for C1 than for C2. Generally, as the pump frequency of the MAX660 in- creases, the capacitance values required to maintain comparable ripple and output resistance diminish proportionately. The curves of Figure 2 show the total circuit output resistance for various Capacitor values (the pump and reservoir capacitors values are equal) and oscillator frequencies. These curves assume 0.250 capacitor ESRs and a 5.25Q MAX660 output resistance, which is why the flat portion of the curve shows a 6.5Q (Ro MAX660 + 4 (ESRC1) + ESRC2) effective output resistance. Note: RO = 5.25Q is used, rather than the typical 6.5Q, because the typical specification inctudes the effect of the ESRs of the capacitors in the test circuit. To reduce the output ripple caused by the charge pump, increase the reservoir capacitor C2 and/or reduce its ESR. Also, the reservoir capacitor must have low ESR if filtering high-frequency noise at the output is important. sw En nn x DZ Ct Sz #2 eo S$ 5 - DP AS = 5kHz 2kHz kHz g 3 ESR = 02502 = FOR BOTH 2 C1 AND C2 & 8 MAX660 OUTPUT 5 SOURCE RESISTANCE 3 ASSUMED TO BE = 5 2502 = 2 oO z = 1 2 4 6810 100 1000 CAPACITANCE (iF) L Figure 2. Total Output Source Resistance vs. C1 and C2 Capacitance (C1 = C2) MVIA KI svCMOS Monolithic Voltage Converter Not all manufacturers guarantee capacitor ESR in the range required by the MAX660. In general, capacitor ESR is inversely proportional to physical size, so larger capacitance values and higher voltage ratings tend to reduce ESR. The capacitors used when testing the MAX660 are MAXC001 150puF aluminum electrolytics available from Maxim. They combine low cost, a guaran- teed maximum ESR of 0.2Q at room temperature, and a low-temperature operating limit of -25C. If operation at lower temperatures is required, certain tantalum capacitors provide good low-temperature ESR, but at added expense. The following is a list of manufacturers who provide low-ESR electrolytic capacitors. MANUFACTURER CAPACITOR CAPACITOR TYPE Ihinois Capacitor RZS Aluminum Electrolytic Mallory TOC &TDL = Tantalum Nichicon PF & PL Aluminum Electrolytic Sprague ora ei Aluminum Electrolytic Sprague ene Tantalum United Chemi-con LXF & SXF Aluminum Electrolytic Cascading Devices To produce larger negative multiplication of the initital supply voitage, the MAX660 may be cascaded as shown in Figure 3. The resulting output resistance is ap- proximately equal to the sum of the individual MAX660 Rout values. The output voltage, where n is an integer representing the number of devices cascaded, is defined by VOUT = -n (VIN). +VIN ~ 8 8 2 AAAXIAA MAX660 Ct : MAX660 "4 5 4 fs Vout 7 Vout = -AVIN Figure 3, Cascading MAX660s to Increase Output Voltage MIA XIsVI Paralieling Devices Paralieling multiple MAX660s reduces the output resis- tance. As illustrated in Figure 4, each device requires its own pump capacitor C1, but the reservoir capacitor C2 serves all devices. The value of C2 should be increased by a factor of n, where nis the number of devices. Figure 4 shows the equation for calculating output resistance. Combined Positive Supply Multiplication and Negative Voltage Conversion This dual function is illustrated in Figure 5. In this circuit, capacitors C1 and C3 perform the pump and reservoir functions respectively for generation of the negative volt- age. Capacitors C2 and C4 are respectively pump and reservoir for the multiplied positive voltage. This circuit configuration, however, leads to higher source impedan- ces of the generated supplies. This is due to the finite impedance of the common charge-pump driver. ____ Rour (of MAX660) UT = (NUMBER OF DEVICES) 2] MAM 2 MAXG6O | fe al +VIN 8 2 = a ; i , D1, 02 = 1N4148 + T cq MAX660 }5 of ae a Vout = -Vin = 4 6 + EE = be Vout = (2Vin) ~ _} 4 Pie (Venn) -(Ve02) C3 T C4 Figure 5. Combined Positive Multiplier and Negative Converter 4-123 O99XVINMAX660 CMOS Monolithic Voltage Converter Chip Topography NOTE: ALL 150uF CAPACITORS ARE MAXCO01, AVAILABLE FROM MAXIM. Figure 6. MAX660 generating 4 +5V regulated output from a ouT 3V Lithium battery. Operates for 16 hours with 4OmA load. 0.072" (1.83mm) 1M 1M AMY VW a iNsat7 OPEN-DRAN L. FC LOW-BATTERY ~ [ | 3 OUTPUT CAP+ 8V/100mA 3 af sty 88 our f a 1502 150 * 150 _ THE ey ipo} + 4 is oD 3V LITHIUM | AAADOLAA MALOOAA GND: 0.114" BATTERY, MAX660 MAX667 nee nan stom DURACELL SET ; (290mm) DL123A osc GND SHON wi 5 7 75 cap. etw Maxim cannol assume responsibility for use of any circuitry other than circuilry 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 lime. 4-124 MMA AISYI