MAA AL/VI +-5V to+10V Voltage Converter ______ (VW Crd General Description Fea tures. = The MAX680 is a monolithic CMOS dual charge @ 95% Voltage Conversion Efficiency > pump voltage converter that provides +10V outputs # 85% Power Conversion Efficiency from an input voltage of +5V, using four external capacitors. The MAX680 provides both a positive @ Wide Voltage Range: +2.0V to +6.0V step-up charge pump to develop +10V from the +5V input and an inverting charge pump to generate the Only Four External Capacitors Required -10V output. The MAX680 includes an on-chip 8kHz @ 500A Supply Current oscillator and all the necessary circuitry (except the four capacitors) to produce both positive and nega- Monolithic CMOS Design tive voltages from a single positive supply. The output source impedances are typically 1509, providing useful output currents up to 10mA. The ______sdaPOrdering Information os9ox low quiescent current and high efficiency make this device suitable for a variety of applications that need CQ PART TEMP. RANGE PACKAGE both positive and negative voltages generated froma MAX680C/D OC to +70C ~s~Diice single supply. MAX680CPA 0C to+70C ~B Lead Plastic DIP Applications MAX6B0CSA 0Cto+70C 8 Lead Small Outline The MAX680 can be used wherever a single positive MAX680EPA -40C to +85C = 8 Lead Plastic DIP supply is available and positive and negative volt- MAXGB0EJA ~40C to +85C 8 Lead CERDIP ages are required. Common applications include the Ky ~ - . generation of +6V from a 3V battery and generation <| AX680ESA 740C to +85C 8 Lead Small Outline of +10V from the standard +5V logic supply for use MAX680MJA -55C to +125C += 8 Lead CERDIP with analog circuitry. Typical applications include: +10V from +5V Logic Supply +6V from a 3V Lithium Cell Handheld Instruments Typical Operating Circuit Battery Operated Equipment Data Acquisition Systems Panel Meters Operational Amplifier Power Supplies +5 LL Ata Pin Configuration Vec . fer Top View Atak v +10 Cl- naxian " e Va C2* MAX680 - -10y ci-[ | | ve te te GND ce+[_| MAXIM | Cit 41k SE MAX680 ce-L_| | Voc ena ana V- GND U L | +5V to +10V Converter MAAN Maxim Integrated Products 6-81 MAXIM is a registered trademark of Maxim Integrated Products.MAX680 +5V tot10V Voltage Converter ABSOLUTE MAXIMUM RATINGS V- Short Circuit Duration Vt Current Vec dv/dT +6.2V Storage Temprature ........... 00.00 eee ee eee -65C to +160C +12V Lead Temperature (Soldering, 10 sec) ...........-..00. +300C -12V Power Dissipation Continuous Plastic DIP (derate 8.33mW/C above +50C) ........ 625mW 75mA Small Outline (derate 6mMW/C above +50C) 1V/us CERDIP (derate 8mW/C above +50C) ............. Stresses above those iistad under Absolute Maximum Ratings may cause parmanent damage to the device. These are stress ratings only, and functional operation of the device at these or any ather conditions above those indicated in the operational! sections of the specifications is not implied. Exposure to absolute maximum ratings conditions for extanded periods may affect device reliability. ELECTRICAL CHARACTERISTICS (Voc = +5V, Ta = +25C, test circuit figure 1, unless noted) | PARAMETER ' SYMBOL CONDITIONS MIN. TYP MAX. | UNITS Voc = 3V, Ta = +25C, Ri = 0.5 1 Vec = 5V, Ta = +25C, RL = @ 1 2 Supply Current lec Voc = 5V, OC = Ta < +70C, RL= 25 mA Voc = SV, -40G < Ta < +85C, RL = 3 | Veo = SV, -55C < Ta +125C, RL = 3 Supply Voltage Range vr MIN. < Ty = MAX. 2.0 15to6.0 6.0 Vv It = 10mA, IL- = OMA, Voc = BV, Ta = +25C 150 250 IL* = 5mA, IL = OMA, Voc = 2.8V, Ta = +25C 180 300 Positive Charge Pump R - IL* = 10mA, IL~ = OMA, Voc = SV, Output Source Resistance our 0C < Ta < +70C 325 2 -40C < Tp < +85C 350 -55C S Ta < +125C 400 IL* = 10mMA, IL- = OMA, Vt = 10V, Ta = +25C 90 150 IL = SMA, IL" = OMA, V* = 5.6V, Ta = +25C 110 175 Negative Charge Pump Rour i," = 10mA, IL- = OMA, Vt = 10V, Output Source Resistance out OC < Ta S$ +70C 200 2 -40C <= Ta = +85C 200 -55C < Ta S$ +125C 250 Oscillator Frequency fosc 4 8 kHz Power Efficiency Perr Ry, = 10kN 85 % Voltage Conversion Loy, vt RL a2 95 99 % Efficiency | EFF V7, RL = ; 90 97 | Typical Operation Characteristics OUTPUT RESISTANCE vs. Voc Vout vs. LOAD CURRENT SUPPLY CURRENT V8. Voc 250 10 20 1-06 = WDpF 200 a = = 15 3 8 = = 150 = z 2 ET B 1 = in = z mee 5 j 3 3 four 06 50 5 0 4 28 36 40 58 60 20 30 40 $0 60 Vee () LOAD CURAENT [mA] Vec () 6-82 MAXIM+5V to+10V Voltage Converter OUTPUT VOLTAGE vs. OUTPUT CURRENT FROM V+ TO V- OUTPUT SOURCE RESISTANCE vs. TEMPERATURE Typical Operation Characteristics OUTPUT RIPPLE vs. OUTPUT CURRENT Ct CA =10pF Ver =5 150 \Wour! () yr OUTPUT SOURCE RESISTANCE ($2) 3 03, C4 = Hpk Rout OUTPUT RIPPLE (mVer - Pxt 0 5 10 -h0 -25 0 OUTPUT CURRENT {mA} From * TO V- Detailed Description All the circuitry needed to implement a voltage quadrupler is contained in the MAX680. Only four external capacitors are needed. These may be inex- pensive polarized electrolytic capacitors with values in the range of 0.1uF to 100pF. Figure 2A illustrates the idealized operation of the positive voltage converter. The on-chip oscillator generates a 50% duty cycle clock signal. During the first half of the cycle, switches S2 and S4 are open, switches S1 and $3 are closed, and the capacitor C1 is charged to the input voltage Voc. During the second half cycle, switches S1 and S3 are open, S2 and S4 are closed, and the capacitor C1 is translated upward by Vcc volts. Assuming ideal switches and no load on C3, charge is transferred onto C3 from C1 such that the voltage on C3 will be 2Vcc, gene- rating the positive supply. Figure 2B illustrates the negative converter. The switches of the negative converter are out of phase from the positive converter. During the second half of the clock cycle, S6 and S8 are open, S5 and S7 are closed, thus charging C2 from V+ (pumped up to 2Vcc by the positive charge pump) to GND. In the first half of the clock cycle, S5 and S7 are open, S6 MAXIM 425 +500 +75 +100 +125 5 10 15 20 TEMPERATURE | C] DUTPUT CURRENT (mal it OR LM Yeo 18 -_<@@ @@ ChE lye Ci- ve * OUT 2 oa oe Rat C2 >= 10, 10uF Tt 8 Vee Nye eno T GND MAXIM iL 6a ts - MAX680 owe 42 5}. tr V- OUT Figure 1. Test Circuit and S8 are closed, and the charge on C2 is trans- ferred to C4, generating the negative supply. The eight switches are CMOS power MOSFETs. Switches $1, S2, S4 and S5 are P-channel devices while switches S3, S6, S7, and S8 are N-channel devices. 6-83 O89SXVNMAX680 +5V tot+10V Voltage Converter Figure 2A. Positive Charge Pump & Cit 82 Vee oo 4 8 oto GND 2 eo 4. We +(Sa, | C= W \3 AL ot 2 Rt- | Ia wl 3 Figure 2. ldealized Voltage Quadrupler Efficiency Considerations Theoretically a charge pump voltage multiplier can approach 100% efficiency under the following condi- tions: The charge pump switches have virtually no offset and extremely low on resistance @ Minimal power is consumed by the drive circuitry The impedances of the reservoir and pump capaci- tors are negligible For the MAX680, the energy loss per clock cycle is the sum of the energy !oss in the positive and nega- tive converters as below: Losstor = Losspos + LoSSNEG = %Cy[(Vt)2 - 2(V")(Voo)] + YeCal(Vt)2 - (V-)2] There will be a substantial voltage difference between (V* - Voc} and Vcc for the positive pump and between V~ and V- if the impedances of the pump capacitors C1 and C2 are high with respect to their respective output loads. Larger values of reservoir capacitors C3 and C4 will reduce output ripple. Larger values of both pump and reservoir capacitors improve the efficiency. Maximum Operating Limits The MAX680 has on-chip zener diodes that clamp Voc to approximately 6.2V, V+ to 12.4V, and V- to -12.4V. Never exceed the maximum supply voltage or excessive current may be shunted by these diodes, potentially damaging the chip. The MAX680 will operate over the entire operating temperature range with an input voltage of 2V to 6V. 6-84 Applications Positive and Negative Converter The most common application of the MAX680 is as a dual charge pump voltage converter which provides positive and negative outputs of two times a positive input voltage. The simple circuit of Figure 3 shows that only four external components are needed, capacitors Ctsand C3 for the positive pump and C2 and C4 for the negative pump. In most applications all four capacitors are low-cost 10uF or 22uF polarized electrolytics. For applications where PC board space is at a premium and low currents are being drawn Cl Se 22uF cl- ve V+ QUT co cz ore ee F od +O Ze Ce x 22pF 3 6 C2- Vec Vec IN 4 5 v- GND [500 MAKIN eno ~ MAX680 V- OUT Figure 3. Positive and Negative Converter MAXIM+5V to+10V Voltage Converter Ci- ve C2+ Ci+ c2- Vee v- OND MAXIM MAX680 Ve OUT 2uF Vcc IW V- OUT Figure 4. Paraileling MAX680s For Lower Source Resistance from the MAX680, 1uF reservoir capacitors may be used for the pump capacitors C1 and C2, with 4.7pF reservoir capacitors C3 and C4. Capacitors C1 and C3 must be rated at 6V or greater, and capacitors C2 and C4 must be rated at 12V or greater. The MAX680 is NOT a voltage regulator; the output source resistance of either charge pump is approxi- mately 150 ohms at room temperature with Vcc at 5V. This means that with an input Vcc of 5V, under light load V* will approach +10V and V- will be at -10V, but BOTH V* and V- will droop towards GND as the current drawn from EITHER V* or V- increases, since the negative converter draws its power from the out- put of the positive converter. To predict the output voltages, treat the chip as two separate converters and analyze them separately. First, the droop of the negative supply (Vprop~) equals the current drawn from V- ~ (IL-) times the source resistance of the negative converter (RS~): Vprop = IL-7 * RS~ Likewise, the droop of the positive supply (Vpropt) equals the current drawn from the positive supply (I_*) times the source resistance of the positive con- verter (RS*), except that the current drawn from the positive supply is the sum of the current drawn by the load on the positive supply (IL*+) plus the current drawn by the negative converter ({L~): Vprop* = IL* x RS* = (IL* + IL7) x RS* The positive output voltage will be: Vt = 2Vcc - Voropt The negative output voltage will be: V- = -(V+ - Vorop) = -(2Vcc - Vorop* - VproP) MAXIM The positive and negative charge pumps are tested and specified separately to provide the separate values of output source resistance for use in the above formulas. When the positive charge pump is tested, the negative charge pump is unloaded, and when the negative charge pump is tested, the positive supply Vt is from an external source, isolating the negative charge pump. The ripple voltage on either output can be calculated by noting that the current drawn from the output is supplied by the reservoir capacitor alone during one half cycle of the clock. This results in a ripple of: Vaippce = lout (1/fpump) (1/CR) For the nominal feump of 8kHz with 10uF reservoir capacitors, the ripple will be 30mV with lout at 5mA. Remember that in most applications, the lout of the positive charge pump is the load current PLUS the current taken by the negative charge pump. Paralieling Devices Paralleling multiple MAX680s reduces the output re- sistance of both the positive and negative converters. The effective output resistance is the output resist- ance of a single device divided by the number of devices. As illustrated in Figure 4, each MAX680 requires separate pump capacitors C1 and C2, but all can share a single set of reservoir capacitors. +5V Regulated Supplies From A Single 3V Battery Figure 5 shows a complete +5V power supply using one 3V battery. The MAX680 provides +6V at V which is regulated to +5V by the MAX666 and -6V which is regulated to -5V by the MAX664. The 6-85 OsoxVWMAX680 +5V to+10V Voltage Converter LOW BATTERY C.. WARNING AT 25 Ls0 LBl SENSE g 2Mn +12y TO +BV main MAX666 4 < 100uF >= al : == wow ic 3 ti E 1 ve e 1.2M0 100.F T tir Maxim Vin Your +6V GHD SON VseT WW 4 F I C2 MAX680 E 100..F = IH tT 10uF > CT] GNO SDN Vser 1OuF = 7 MAXIM MAX664 ba [* ~12y TO -6V Vin Vour | Vout 2 Py ~bV SENSE Figure 5. Regulated +5V and -5V From a Single Battery MAX666 and MAX664 are pre-trimmed at wafer sort and require no external setting resistors, minimizing parts count. The combined quiescent current of the MAX680, MAX663, and MAX664 is less than 500uA, while the output current capability is 5mA. The input ta the MAX680 can vary from 3V to 6V without affect- ing regulation appreciably. With higher input voltage, more current can be drawn from the outputs of the Chip Topography c2+ Ci- vt Ci+ Note: Connect substrate to V* MAX680. With 5V at Voc, 10mA can be drawn from both regulated outputs simultaneously. Assuming 150 ohm source resistance for both converters, with (IL* + IL-) = 20mA, the positive charge pump will droop 3V, providing +7V for the negative charge pump. The negative charge pump will droop another 1.5V due to its 10mA load, leaving -5.5V at V-, sufficient to maintain regulation for the MAX664 at this current. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. Na circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. SU AXLWVI