19-0915; Rev 0; 5/66 MAAKIM CMOS Micropower Step-Up Switching Regulator General Description Maxim's MAX630 and MAX4193 CMOS DC-DC regulators are designed for simple, efficient, minimum size DC-DC converter circuits in the 5 milliwatt to 5 Watt range. The MAX630 and MAX4193 provide all control and power handling functions in a compact 8 pin package: a 1.31V bandgap reference, an oscillator, a voltage comiparator, and a 375mA N-channel outout MOSFET. A comparator is also pro- vided for low battery detection. Operating current is only 70uzA and is nearly inde- pendent of output switch current or duty cycle. A logic level input shuts down the regulator to less than 1A quiescent current. Low current operation ensures high efficiency even in low power battery operated systems. The MAX630 and MAX4193 are Features High Efficiency85% Typical @ 704A Typical Operating Current @ 1pA Maximum Quiescent Current @ 2.0 to 16.5V Operation @ 525mA (Peak) Onboard Drive Capability +1.5% Output Voltage Accuracy (MAX630) @ Low Battery Detector @ Compact 8 Pin Mini-DIP and SO Packages @ Pin Compatible With RC4191/2/3 compatible with most battery voltages, operating Ordering information from 2.0V to 16.5V. The devices are pin compatible with the Raytheon PART TEMR RANGE 8 Lead PACKAGE bipolar circuits, Ros ow/2/3, while providing signifi- MAX630CPA oC to +70C =: & Lead Plastic DIP cantly improved efficiency and low voltage operation. MAX630CSA 0C to +70C aL 7 Maxim also manufactures the MAX631, MAX632, and on oad Smal! Cutting MAX633 DC-DC converters which reduce the ex- MAX630CJA OCto+70C BB Lead CERDIP ternal component. count in fixed output 5V, 12V, and MAX630EPA ~40C to +85C 6 Lead Plastic DIP 18V circuits. See Table 2 on the last page of this data MAX630E: 0 ; sheet for a summary of other Maxim DC-DC SA 40C 10 ESC _B Load Small Outline converters. MAX630EJA -40C to+85C = B Lead CERDIP MAX630MJA = -55C to +125C = 8B Lead CERDIP MAX4193C/D OC to+70C ~ Dice Applications MAX4193CPA OC to+70C - 8 Lead Plastic DIP +5V to +15V DC-DC Converters MAX4193CSA 0C to +70C & Lead Small Outline High Efficiency Battery Powered MAX4193CUA OC to +70C. 8 Lead CERDIP DC-DC Converters MAX4193EPA -40C to +85C 8 Lead Plastic DIP +8V to +5V DC-DC Converters MAX4193ESA -40C to +85C = 8 Lead Small! Outline 9V Battery Life Extension MAX4193EJA = -40C to +85C = 8 Lead CERDIP Uninterruptible 5V Power Supplies MAX4193MJA = -55C to +126C = 8 Lead CERDIP. 5mW to 5 Watt Switch-mode Power Supplies Typical Operating Circult Pin Contiguration ~_m Top View . 4 LBR | fe] LBD MAXIM AAAXIM ; MAX630 Br + Cx] waxeao [7 ]re *e out MAX4193 uxL2] [etc i = ano [=| [5] Vs 1 = +V to +15V Converter SVIA AISI Maxim Integrated Products MAXI iS a registered trademark of Maxim Integrated Products. E6GLPXVIN/OEOXVNMAX630/MAX4193 CMOS Micropower Step-Up Switching Regulator ABSOLUTE MAXIMUM RATINGS Supply Voltage ....--. 2. eee ene eee ees Dees ve eunenee 18V Storage Temperature Range ...........-06+ ~65C to +160C Lead Temperature (Soldering, 10 seconds) ........... +300C Operating Temperature Range . MAX630C, MAX4199C 10... .. cece eee eee eee 0C to +70C MAX630E, MAX4193E .... cece cena eens -40C to +85C MAX630M, MAX4193M) wc ee cee eee -55C to +125C Power Dissipation Plastic DIP (derate 6.25mW/C above 50C) ........ 468mW Small Outline (derate 5.88mW/*C above 50C) ...... 44imw CERDIP. (derate 8.33mW/"C above 50C) ......-.4- a3amw Input Voltage (Pins 1, 2, 6, 7) Output Voltage, Ly and LBD : _18V Ly Output Gurrent. tees .. 525mA Peak , LBD Output Current. oS ce cee rece eeee 5OmA Stresses above those listed under Absolute Maximum Alatings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is noe implied. Exposure to absolute maximum ratings conditions for extended periods may affect device reliability. . ELECTRICAL CHARACTERISTICS (+Vg = +6.0V, Ta = +25C, Ig = 5.0uA, unless otherwise noted) MAX630 MAX4193 PARAMETER SYMBOL _ CONDITIONS MIN. TYR MAX.| MIN. TYR MAX. UNITS Operating 2.0 165 | 24 16.5 Supply Voltage Wes Start-up 18 Vv Internal Reference Voltage Vrer 129 1.31 1.33) 1.24 = 1.31 1.38 Vv Switch Current sw V3 = 400mV 76 160 75 150 mA Supply Current (at Pin 5) Ig lg = OmA 70 125 90 wA Efficiency 85 85 % Line Regulation (Note 1) 0.5Vy < Vg < Vy 008 862 0.08 8605 | %Vour Load Regulation {Note 1) Vg = +5, Poa = Oto 150mW.: 02 085 02 05 | %Vour Operating Frequency Range (Note 2) Fo 01 4Q 75 0.17 25 75 kHz Reference Set Interna! - Pulldown Resistance Ric Vg = Vs 0.5 15 10 05 1.5 10 Mo Reference Set Input Voltage Threshold Vic 0.2 0.8 1.3 0.2 0.8 1.3 Vv Switch Current sw Vg = 1.0V 100 100 mA Switch Leakage Current leo V; = 16.5V 0.01 1.0 0.01 5.0 HA Supply Current (Shut Down) Iso I< 0.01nA 0.01 1.0 0.01 5.0 BA Low Battery Bias Current lLer 0.01 10 0.01 10 nA Capacitor Charging Current lox 30 30 hA Cy + Threshold Voltage +Vg - 0.1 +Vg- 0.1 Vv Cy - Threshold Voltage 01 0.1 Vv Veg Input Bias Current lee 0.01 10 0.01 10 nA Low Battery Detector Vz = 0.4V, Output Current leo [yi=qiv 250 600 250600 HA Low Battery Detector Vg = 16.5V, Output Leakage liepo | vy=14V aa 5.0 oot 5.0 | HA Note 1: Guaranteed by correlation with DC pulse measurements. ; Note 2: The operating frequency range is guaranteed by design and verified with sample testing. 2 MAXIM* ELECTRICAL CHARACTERISTICS | (+Vg = +6.0V, Ta = F ull Operating Temperature Range, tc = 5.0uA, unless otherwise noted) CMOS Micropower Step-Up Switching Regulator MAX830 MAX4193 ; PARAMETER SYMBOL CONDITIONS MIN. TYP MAX. |MIN. TYR MAX. UNITS. Supply Voltage +Vg 2.2 16.5 3.6 16.5 Vv Internal Reference Voltage Vaer 1250-13100 (1.37) {12000 1.31 (1.42 Vv Supply Current (Pin 5) Ig Ig = OMA 70 200 90 300 BA Line Regulation (Note 1) 0.5Vour< Vs < Vout 0.2 05 05 1.0 | % Vour Load Regulation (Note 1) Vg = +0.5Vo, PL = 0 to 150mW 0.5 1.0 0.5 1.0 | % Vout . . Ve=Vs Reference Set Internal R OC ST, Ss +70C 0.45 1.6 10: 0.45 16 10 Mo Pulldown Resistance 1e -40C < Ty S +85C 0.4 1.5 10) 0.4 16. 10 55C <= Ty 5 +125C 0.3 15 * 10 0.3 1.5 10 Reference Set Input Voltage Threshold Vic 0.2 0.8 1.3 0.2 08 1.3 v Switch Leakage Current loo Vg = 16.5V 0.1 30 0.1 30 BA Supply Current (Shut Down) Iso Ip < 0.01pA 0.01 10 0.01 30 pA Low Battery Detector _ _ Output Current liso Vg = 0.4V, Vy = 1.1V 250 600 250 600 pA Note 1: Guarantesd by correlation with DC pulse measurements. ! Pin Description PIN NAME FUNCTION PIN NAME FUNCTION 1 LBR | Low Battery Detection Comparator 6 le The MAX630/MAX4193 shuts down when input.The LBD output, pin 8, sinks current this pin is left floating or is driven below when ever this pin is below the low battery 0.2V. For normal operation connect I, detector threshold, typically L.31V. directly to +V, or drive it high with either a CMOS gate or pull-up resistor connected to +Vs, The supply current is typically 2 Cx An external capacitor connected between Ss this terminal and ground sets the 1OnA in the shutdown mode. oscillator f . A7pF = 40KHz. somator irequency. /p OKHaz, 7 Vep The output voltage is set by an external oo. . . resistive divider connected from the 3 Ly This pin drives the external inductor. The converter output to Veg and Ground, The internal N-channel MOSFET which drives MAXB30/MAX4193 will pulse the L, output L, has an output resistance of 4 ohms and whenever the voltage at this terminal is a peak current rating of 525mA. less than 1.31V. 4 GND | Ground. 8 LBD | The Low Battery Detector output is an open drain N-channel MOSFET which 5 +V. The positive supply voltage, from 2.0V to sinks up to 600 uA (typ) whenever the LBR 8 1esv (M AX630). y 9 input, pin 1, is below 1.31V. 61 /XVN/OCOXVNMAX630/MAX4193 CMOS Micropower Step-Up Switching Regulator Lx ON RESISTANCE ve. TEMPERATURE Ltn fal - un Wg = AK A 8 3 i TEMPERATURE (0) 1 Detailed Description The operation of the MAX630 can best be under- stood by examining the voltage regulating loop of Figure 1. R1 and R2 divide the output voltage, which is compared with the 1.3V internal reference by comparator COMP1. When the output voltage is lower than desired, the comparator output goes high and the oscillator output pulses are passed through the NOR gate latch, turning on the output N-channel MOSFET at pin 3, Ly. As long as the output voltage is less than the desired voltage, pin 3 drives the inductor with a series of pulses at the oscillator frequency. Each time the output N-channel MOSFET is turned on, the current through the external coil, L1, in- creases, storing energy in the cail. Each time the output turns off, the voltage across the coil reverses sign and the voltage at Ly rises until the catch diode, D1, is forward biased, delivering power to the output. When the output voltage reaches the desired level, 1.31V x (1 + RA1/R2)}, the comparator output goes low and the inductor is no longer pulsed. Current is then supplied by the filter capacitor, C1, until the output voltage drops below the threshold, and once again Ly is switched on, repeating the cycle. The average duty cycle at Ly is directly proportional to the output current. Output Driver (Lx Pin) The MAX630/MAX4193 output device is a large N-channel MOSFET with an -ON resistance of 4 ohms and a peak current rating of 525mA. One well known advantage that MOSFETs have over TEMPERATURE (C) Typical Operating Characteristics SUPPLY CURRENT ve. SUPPLY VOLTAGE bipolar transistors in switching applications is higher speed, which reduces switching losses and allows the use of smaller, lighter, less costly magnetic com- ponents. Also important is that MOSFETs, unlike bipolar transistors, do not require base current which, in low power DC-DC converters, often ac- counts for a major portion of input power. The operating current of the MAX630 and MAX4193 increases by approximately 1uA/kHz at maximum power output due to the charging current required by the gate capacitance of the Ly output driver (e.g.. 40uA increase at a 40kHz operating frequency). In comparison, equivalent bipolar circuits typically drive their NPN Ly output device with 2mA of base drive, causing the bipolar circuit's operating current to increase by a factor of 10 between no load and full load: Oscillator The oscillator frequency is set by a single external, low cost ceramic capacitor connected to pin 2, Cy. 47pF sets the oscillator to 40kHz, a reasonable.com- promise between lower switching losses at low fre- quencies and reduced inductor size at higher frequencies. Low Battery Detector The low battery detector compares the voltage on LBR with the internal 1.31V reference. The output, LBD, is an open drain N-channel MOSFET. In addi- tion to detecting and warning of a low battery vol- tage, the comparator can also perform other voltage monitoring operations such as power failure detection. MMAXIMMCMOS Micropower Step-Up Switching Regulator __ ANAXKIM +5 INPUT MAX630 LBO 8 LOW BATTERY OUTPUT nM EATTERY PUT sf usr . > (ow iF iaPuT < 34) RB come 2 BK ; wea iW | 3 ul = 470 - Re cy eh * i Wie rae SUL COMP 1 tom + = akhz cc! > ako anu ES SHUTDOWN x ig [6 +-~4 e m Ts wren 1watas Row = 30 Lat BANDGAP co END REFERENCE Nels AND = = BIAS GENERATOR +15V-OUTPUT tt 20m =m 0) = 470uF aay Figure 1. +5V to +15V Converter and Block Diagram External Components Another use of the low battery detector is to lower : Resistors the oscillator frequency when the input voltage goes below a specified level. Lowering the oscillator fre- quency increases the available output power, com- pensating for the decrease in available power caused by reduced input voltage (See Figure 5). Logle Level Shutdown Input The shutdown mode is entered whenever Ic (pin 6) is driven below 0.2V or left floating. When shut down, the MAX630s analog circuitry, oscillator, Ly and L&D outputs are turned off. The device's quiescent current during shutdown is typically 10nA (1nzA max). Bootstrapped Operation In most circuits, the preferred source of +Vg voltage for the MAX630 and MAX4193 is the boosted output voltage. This is often referred to as a bootstrapped operation since the circuit figuratively lifts itself up. The ON resistance of the N-channel Ly output de- creases with an increase in +Vs, however, the device operating -current goes up with +Vg (see typical operating graph, Is vs. +Vg). In circuits with very low output current and input voltages greater than 3V it may be more efficient to connect +Vg directly to the input voltage rather than bootstrap. Since the LBR- and Vrs input bias currents are specified as 10nA maximum, the current in the dividers R1/R2 and R3/R4 (figure 1) may be as low as ipzA without significantly affecting accuracy. Normally R2 and R4 are between 10k ohms and 1M ohm, which sets the current in the voltage dividers in the 1.3yA to 130A range. R1 and R3 can then be calculated as follows: 1OkO<R2<1MQ- R1= RQ x VOUT 1SIV ~ - 1.31V Vip - 131V 10kN<RA4<S1MO AB = Ag x EBT ISIV 1.31V Where Vout is the desired output voltage and Vig is the desired low battery warning threshold. lf the [ (shutdown) input is pulled up through a resistor rather than connected directly to +Vs, the current through the pullup resistor should be a minimum of 4uA with Ic at the input-high threshold of 1.3V: 4+Vg-1.3V < RicS 4nA EGLPXVN/OECOXVNMAX630/MAX4193 CMOS Micropower Step-Up Switching Regulator inductor Value The available output current from a DC-DC voltage boost converter is a function of the input voltage, external inductor value, output voltage and the oper- ating frequency. The inductor must 1) have the correct inductance, 2) be able to handle the required peak currents, and 3) have acceptable series resistance and core losses. If the inductance is too high, the MAX630 will not be able to deliver the desired output power, even with the Lx output on for every oscillator cycle. The available output power can be increased by either decreasing the inductance or the frequency. Re- ducing the frequency increases the on-period of the .Ly output, thereby increasing the peak inductor cur- rent. The available output power is increased since it .i8 proportional to the square of the peak inductor current (Ipx). Letay = WIN Ton)? f MAX " 2 Pout Ll pk? f 2 Vin Ton L since: Pout = and: Ink = Where Pout includes the power dissipated in the catch diode (D1) as well as that in the load. If the inductance is too low, the current at Lx may exceed the maximum rating. The minimum allowed inductor value is expressed by: _ Vin Ton Lain = IMAX Where Iax = |525mA\ (peak Lx current) and Ton is the on-time of the Ly output. The most common MAX630 circuit is a boost mode converter (Figure 1). When the N-channel output device is on, the current linearly rises since: |. i ri[< At the end of the on-time (14s for 40kHz, 55% duty cycle oscillator) the current is: VTon _ 5V x 14us lok T= Gap 7 150MA. The energy in the coil is: L lox? = EE = 5.28, At maximum load this cycle is repeated 40,000 times per second, and the power tranferred through the coil is 40,000x5.25 = 210mW. Since the coil only supplies the voltage above the input voltage, at 15V, the DC-DC converter can supply 210mW/ (15V-5V) = 21mA. The coil provides 210mW and the ' battery directly supplies another 105mW, for a total of 315mW of output power. If the load draws less than 21mA, the MAX630 turns on its output only -often enough to keep the output voltage at a constant 15V. Reducing the inductor value increases the available output current: jower L increases the peak current, thereby increasing the available power. The external inductor required by the MAX630 is readily obtained from a variety of suppliers. (See Table 1). Standard coils are suitable for most applications. Types of inductors Molded Inductors These are cylindrically wound coils which look similar to 1 watt resistors. They have the advantages of low cost and ease of handling, but have higher resistance, higher losses, and lower power handling capability than other types. Potted Toroidal inductors A typical 1mH, 0.82 ohm potted toroidal inductor (Dale TE-3Q4TA) is 0.685 in diameter by 0.385" high and mounts directly onto a printed circuit board - by its leads. Such devices offer high efficiency and mounting ease, but at a somewhat higher cost than molded inductors. Ferrite Cores (Pot Cores} Pot cores are very popular as switch-mode inductors since they offer high performance and ease of design. The coils are generally wound on a plastic bobbin, which is then placed between two pot core sections. A simple clip to hold the core sections together completes the inductor. Smaller pot cores mount directly onto printed circuit boards via the bobbin terminals. Cores come in a wide variety of sizes, often with the center posts ground down to provide an air gap. The gap prevents saturation while accurately defining the inductance per turn squared. Pot cores are suitable for all DC-DC converters, but are usually used in the higher power applications. They are also useful for experimentation since it is easy to wind coils onto the plastic bobbins. Toroidal Cores In volume production the toroidal core offers high performance, low size and weight, and low cost. They are, however, slightly more difficult for proto- typing, in that manually winding turns onto a toroid is more tedious than on the plastic bobbins used MAAXI/M_CMOS Micropower Step-Up Switching Regulator with pot cores. Toroids are more efficient for a given size since the flux is more evenly distributed than in a pot core, where the effective core area differs between the post, side, top and bottom. Since it is difficult to gap a toroid, manufacturers produce toroids using a mixture of ferromagnetic powder (typically iron or Mo-Permalloy powder) and a binder. The permeability is controlled by varying the amount of binder, which changes the effective gap between the ferromagnetic particles. Mo-Permalloy powder (MPP) cores have lower losses and are recom- mended for the highest efficiency, while iron powder cores are lower cost. Table 1. Coil and Core Manufacturers TYPICAL MANUFACTURER PAR DESCRIPTION MOLDED INDUCTORS Daie IHA-104 500,H, 0.5 ohms Nytronics WEE-470 470zH, 10 ohms TRW LL-500 500,yH, 0.75 ohms POTTED TOROIDAL INDUCTORS Dale TE-3Q4TA 1mb, 0.82 ohms TRW MH-1 600yH, 1.9 ohms Torotel Prod. PT 53-18 500nH, 5 ohms, FERRITE CORES AND TOROIOS Tor. Core, Allen Bradley T0451S100A 500nH/T2 Siemans B64290-K38-X38_ | Tor. Core, 4uH/T? " Tor. Core, Magnetics 555130 53nH/T2 " Pot Core, Staekpole 57-3215 14mm x &mm Magnetics G-41408-25 Pot Core, 14x 8, 250nH/T2 Note: This list does not constitute an endorsement by Maxim Integrated Products and is not intended to be a comprehensive list of all manufacturers of these components. Diodes In most MAX630 circuits, the inductor current re- turns to zero before Ly turns on for the next output pulse. This allows the use of slow turn-off diodes. On the other hand, the diode current abrubtly goes from zero to full peak current each time Ly switches off (figure 1, D1). To avoid excessive losses, the diode must therefore have a fast turn-on time. For low power circuits with peak currents Jess than 100mA, signal diodes such as 1N4148s perform well. MAXIM For higher current circuits, or for maximum effi- ciency at low power, the 1N5817 series of Schottky diodes are recommended. Although 1N4001s and other general purpose rectifiers are rated for high currents, they are unacceptable because their slow turn-on time results in excessive losses. Filter Capecitor The output voltage ripple has two components, with approximately 90 phase difference between them. One component is created by the change in the capacitors stored charge with each output pulse. The other ripple component is the product of the capacitors charge/discharge current and its ESR (effective series resistance). With low cost aluminum electrolytic capacitors, the ESR produced ripple is generally larger than that caused by the change in charge. Vesr = !pk x ESR = iy) x ESR (Volts p-p} Where Vjpn is the coil input voltage, L is its induct- ance, f is the oscillator frequency, and ESR is the equivalent series resistance of the filter capacitor. The output ripple resulting from the change in charge on the filter capacitor is: Vga -2 where, Q = tpis x pest Vv and, Ipeak = tcHa x _ Vin(tcHa)(tois) Vaa 2LC Where tcug and tpig are the charge and discharge times for the inductor (1/2f can be used for nominal calculations). Oscillator Capacitor, Cy; The oscillator capacitor, Cy, is a non-critical ceramic or silver mica capacitor. Cx can also be calculated by: _ 2.14 x 10-6 ; - Cint (Cint = SpF, see text) Cx Where f is the desired operating frequency in Hertz, and Cyr is the sum of the stray capacitance on the Cx pin and the internal capacitance of the package. The internal capacitance is typicaly 1pF for the plas- . tic package and 3pF for the CERDIP package. Typical -stray capacitances are about 3pF for normal printed circuit board layouts, but will be significantly higher if a socket is used. EGLOXVWN/OESOXVNMAX630/MAX4193 CMOS Micropower Step-Up Switching Regulator Bypassing and Compensation Since the inductor charging current can be relatively large, high currents can flow through the ground connection of the MAX630/4193. To prevent unwanted feedback, the impedance of the ground path must be as low as possible, and supply bypassing should be used for the device. When large values (>50k) are used for the voltage setting resistors, R1 and R2 of Figure 1, stray capaci- tance at the Veg input can add a lag to the feedback response, destabilizing the regulator, increasing low frequency ripple, and lowering efficiency. This can often be avoided by minimizing the stray capacitance at the Veg node. It can also be remedied by adding a lead compensation capacitor of 100pF to 10nF in parallel with R14 in Figure 1. ___ DC-DC Converter Configurations DC-DC converters come in three. basic topologies: buck, boost, and buck-boost (figure 2). The MAX630 is usually operated in the positive voltage boost circuit, where the output voltage is greater than the input. The boost circuit is used where the input voltage is always less than the desired output and the buck circuit is used where the input is greater than the output. The buck-boost circuit inverts, and can be used with input voltages which are either greater or less than the output: DC-DC converters can also be classified by the control method. The two most common are pulse width modulation (PWM) and pulse frequency modu- lation (PFM). PWM switch-mode power supply ICs (of which current mode control is one variant) are well established in high power off-line switchers. Both PWM and PFM circuits contro! the output voltage by varying duty cycle. In the PWM circuit the frequency is held constant and the width of each pulse is varied. In the PFM circuit, the pulse width is held constant and duty cycle is controlled by changing the puise repetition rate. The MAX630 refines the basic PFM by employing a constant frequency oscillator. Its output MOSFET is switched on when the oscillator is high and the output voltage is lower than desired. If the output voltage is higher than desired, the MOSFET output is disabled for that oscillator cycle. This pulse skipping varies the average duty cycle, and thereby controls the output voltage. Note that, unlike the PWM ICs which use an op-amp as the control element, the MAX630 uses a compara- tor to compare the output voltage to an onboard reference. This reduces the number of external components, and operating current. BOOST CONVERTER Li 7 7 gn [J enn BUCK CONVERTER . rm Ie > |ver * cron | Nour < Meany Lyf BUCK-BOOST CONVERTER fo 1 . CONTROL A Vaart E SECTION [Mauri < OR > Yaarr it -lh Figure 2. DC-DC Converter Configurations Typical Applications +5V to +15V DC-DC Converter Figure 1 shows a simple circuit which generates +15V at approximately 20mA from a +5V input. The MAX630 has a +1.5% reference accuracy, so the output voltage has an untrimmed accuracy of +3.5% if R1 and R2 are 1% resistors. Other output voltages can also be selected by changing the feedback resistors. Capacitor Cy sets the oscillator frequency (ype -AOkH2), while C1 limits output ripple to about 5Omv. With a low cost molded inductor, the circuit's effi- ciency is about 75%, but an inductor with lower series resistance such as the Dale TE3Q4TA in- creases efficiency to around 85%. A key to high efficiency is that the MAX630 itself is powered from the +15V output. This provides the onboard N-channel output device with 15V gate drive, lowering its ON resistance to about 4 ohms. When +5V power is first applied, current flows through L1 and D1, supplying the MAX630 with 4.4V for startup. MAXLVICMOS Micropower Step-Up Switching Regulator +S5V to + 15V DC-DC Converter The circuit in Figure 3 is similar to that of Figure 1 except that two more windings are added to the inductor. The 1408 (14mm x 8mm) pot core specified is an IEC standard size available from many manufacturers (see Table 1). The -15V output is semi-regulated, typically varying from -13.6V to -14.4V as tne *18V load current changes from no load to 20mA. +5V 2 Mn ey ss Ic + V5 Veg l 26a0 | maxi L MAX630 = 2 tx Cx 1 L | GND aI9F 4 LT Lexo__uo t = 4 8 = 13:3 - t+ one 220 H PRIMARY = 14x 8 mm POT CORE ALL DIODES 1N4148 | Figure 3. +5V to +15V Converter 2% Watt 3V to SV DC-DC Converter Some systems, although battery powered, need high currents for short periods, and then shutdown to a low power state. The extra circuitry of Figure 4 is designed to meet these high current needs. Operat- ing in the buck-boost or flyback mode, the circuit converts -3V to +5V. The left side of the figure is similar to Figure 1, and supplies 15V for the gate drive of the external power MOSFET. This 15V gate drive ensures that the external device is completely turned on and has Jow ON resistance. The right side of Figure 4 is a -3V to +5V buck-boost converter. This circuit has the advantage that-when the MAX630 is turned off the output voltage falls to OV, unlike the standard boost circuit where the output voltage is Vgat7-0.6V when the converter is shutdown. When shutdown, this circuit uses less than 10uA, with most of the current being the leakage current of the power MOSFET. The inductor and output filter capacitor values have been selected to accomodate the increased .power levels. With the values indicated, this circuit can supply up to 500mA at 5V, with an efficiency of 85%. Since the left side of the circuit powers only the right hand MAX630, the circuit will start up with battery voltages as low as 1.5V, independent of the loading on the +5V output. 2 10ka 6 15 3 q4x MAX630 le Ns MAKIM $ 250K A We SHUTOOWN agako < MAXIM ; Vs MAX630 \ralb- re VFB i om z aS +8V AT OSA ,; ye + I I | | 3 ly Ic | | | | | | | | 5 2 &% io . wv 4 LITHIUM | 176 4069 CELL AIpF atk B o> 4 | -av L_ SECTION 1 SECTION 2 J Figure 4. High Power 3V to 5V Converter with Shutdown _ MAXIM EGLPXVN/OESXVNMAX630/MAX4193 CMOS Micropower Step-Up Switching Regulator +3V Battery to +5V DC-DC Converter A common power supply requirement involves con- version of a 2.4 or 3V battery voltage to a 5V logic supply. The circuit in figure 5 converts 3V to 5V at 40mA with 85% efficiency. When Ic (pin 6) is driven low, the output voltage will be the battery voltage minus the drop across diode D1. The optional circuitry using C1, R3, and R4 lowers the oscillator frequency when the battery voltage falls to 2.0V. This lower frequency maintains the output power capability of the circuit by increasing the peak inductor current, compensating for the reduced battery voltage. Ly 47048 INatas Lr LTV p+} t +5V OUT w> 4, 3 = ATIF 15 9 l $ 2akn x I = 5 = i ipa 5 3, MAXIM Ic shen 7 4 = he MAX630 \rq : > 4mke eo cx NO $, 2 2 = | 2 | > 200kn i) L Figure 5. 3V to 5V Converter with Low-Batiery Frequency Shift Uninterruptable +5V Supply In Figure 6 the MAX630 provides a continuous supply of regulated +5V, with automatic switch-over between line power and battery backup. When the line powered input voitage is at +5V, it provides 4.4V to the MAX630 and trickle charges the battery. If the line powered input falls below the battery voltage, the 3.6V battery supplies power to the MAX630, which boosts the battery voltage up to +5V, thus maintaining a continuous supply to the uninter- ruptable +5V bus. Since the +5V output is always supplied through the MAX630, there are no power spikes or glitches during power transfer. The MAX630's low battery detector monitors the line powered +5V, and the LBD output can be used to shut down unnecessary sections of the system during power failures. Alternatively, the low battery detector could monitor the Nicad battery voltage and provide warning of power loss when the battery is nearly discharged. 10 LINE POWERED +5 INPUT UNINTERRUPTABLE san | '4o0! 470, 1N58I7 OUTPUT 18817 3 ae A70uF 1 . , Ly av | 2nd 4/8 = NicAD =" Ty 6 . BATTERY LBR \cf | = 3 MAXIM 3 Kn loan, MAX630 7 q L LBO Vra = ont ox ton 4 2L > tf gm 1 POWER FAIL Figure 6. Uninterruptable +5V Supply Unlike battery backup systems that use 9V batteries, this circuit does not need +12 or +15V to recharge the battery. Consequently, it can be used to provide +5V backup on modules or circuit cards which only have 5V available. 9V Battery Life Extender Figure 7's circuit provides a minimum of 7V until the 9V battery voltage falls to less than 2V. When the battery voltage is above 7V the MAX630's Ic pin is low, putting it into the shutdown mode which draws only 10nA. When the battery voltage falis to 7V, the MAX8212 Voltage Detectors output goes high, enabling the MAX630. The MAX630 then main- tains the output voltage at 7V even as the battery voltage falls below 7V. The low battery detector (LBD) is used to decrease the oscillator frequency when the battery voltage falls to 3V, thereby increas- ing the output current capability of the circuit. Note that this circuit (with or without the MAX8212) can be used to provide 5V from 4 aikaline cells. The initial voltage is approximately 6V, and the output is maintained at 5V even when the battery voltage falls to less than 2V. MAXICMOS Micropower Step-Up Switching Regulator 1.0m# eur 87000 > LYYY\_p} ; BATTERY = | us + 3 5 2 1M T av = : T 3 3 ly h = 3 24M 8 3 13Mn eh , $ Ma toma. \ ANA ? HYST LBR maxim maxim i, MAX8212 OUT MAX630 ta [2 af THRESHOL | , e Simo 3 sun 3 Kn LBo cx eno 3 1 ano 7 ; 7 5 100pF J | i * = a ame Figure 7. Battery Life Extension Down To 3V In Dual Tracking Regulator A MAX634 Inverting Regulator is combined with and R4. Both regulators are set to maximize output a MAX630 in Figure 8 to provide a dual tracking power at low battery voltage by reducing the oscillator +15V output from a 9V battery. The reference for the frequency, via LBR, when Vgatt falls to 72V. -15V output is derived from the positive output via R3 ~ : Ro na INPUT, $V.BATTERY 100k 100k. y wad 500uH Insta NEG OUT FVYY\_ pot POS OUT -12, 15mA ~T_* Ter +12, 45mA 7 25004 we. , m $ T 330uF + 5 |s_|7 |6 5 30 OS 1 = Ly Vea Vner +s fi, e} ts ud, ~ GND lc Veo MAXIM $ RS MAXIM q MAX634 y WOK 4 MAX630 $s 1 ENO 21 by leo UR f= | Cy LBD LBA Er on = 2 je ft 100pF = 150nF | Ti #8 | 7 = VO. == 4mpF Low I EGLPXVW/OESXVUN Figure 8. 12V Dual Tracking Regulator MAXIM 1MAX630/MAX4193 CMOS Micropower Step-Up Switching Regulator Table 2. Maxim DC-DC Converters 0.070" (1.7emm) DEVICE DESCRIPTION INPUT VOLTAGE OUTPUT VOLTAGE COMMENTS ICL7660 Charge Pump Voltage Inverter 1.5V to 10V Vin Not regulated MAX4193 | DC-DC Boost Converter 2.4V to 16.5V Vout > Vin RC4193 2nd source MAX630 DC-DC Boost Converter 2.0V to 16.5V Vout > Vin improved RC4191 2nd source MAX631 DC-DC Boost Converter 1.5V to 5.6V +5V Only 2 external components MAX632 DC-DC Boost Converter 1.5V to 12.6V +12V Only 2 external components MAX633 DC-DC Boost Converter 1.5V to 15.6V +15V Only 2 external components MAX4391 DC-DC Voltage Inverter 4V to 16.5V up to -20V RC4391 2nd source MAX634 DC-DC Voltage Inverter 2.3V to 16.5V up to -20V improved RC4391 2nd source MAX635 DC-DC Voltage Inverter 2.3V to 16.5V -5V Only 3 external components MAX636 DC-DC Voltage Inverter 2.3V to 16.5V -12V Only 3 external components MAX637 DC-DC Voltage Inverter 2.3V to 16.5V -15V Only 3 external components MAX638 DC-DC Voltage Stepdown 3V to 16.5V Vout < Vin Only 3 external components MAX641 High Power Boost Converter 1.5V to 5.6V +8V Drives external MOSFET MAX642 High Power Boost Converter 1.5V to 12.6V +12V Drives external MOSFET MAX643 High Power Boost Converter 1.5V to 15.6V +16V Drives external MOSFET Chip Topography ____C#Packkaaging Information LEAD #1 | 0150-0158 018) -0.205 0.228 - 0.244 (S810 - 4013) (4507 - 5.207) (6.797 - C198) - Oa (osse =045n I =>] foe POR asc G,188 - 0.197 ( - 3 0014 - 0.022 (0358 - 0555) o.p04 - 0.008 | (otc? - 0.203) ta 3-6 0.063 - 0.069 [1.600 - 1.753) 0.007 - 0.009 (0176 - 0.228) B Lead Small Outline (SA) Oia = 170C/W yc = 80C/W See MAXIM Databook for additional package information. 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, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 12 1994 Maxim Integrated Products Printed USA MAXIM js a registered trademark of Maxim Integrated Products.