19-0106; Rev 1; 7/93 MA AMAALM Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring General Description The MAX8213 and MAX8214 contain four precision volt- age comparators capable of monitoring undervoltage and overvoltage conditions for both positive and negative supplies. Accurate trip-point setting is facilitated by the internal 1.25V reference. Not only is trip-level accuracy guaranteed to +1% over the commercial temperature range, but the trip levels of all channels are guaranteed to match each other within 1%. A fifth comparator channel monitors microprocessor voltages and generates delayed reset signals. The MAX8213 has open-drain outputs, while active pull-up outputs are in- corporated in the MAX8214. Applications Microprocessor Voltage Monitoring Precision Battery Monitoring Over/Under/Window Voltage Detection Industrial Controllers Appliances Telephones Portable Computers Mobile Radios Portable Instruments Automotive and Industrial Equipment Pin Configuration Features @ +1% Guaranteed Trip-Level Accuracy over Commercial Temp. Range @ 4 Precision Comparators Plus Auxiliary Comparator @ Built-In Hysteresis @ Internal 1.25V Reference with 0.75% Initial Accuracy +1% Guaranteed Trip-Level Matching Between Channels over Commercial Temp. Range @ Wide Supply Range: 2.7V to 11V Controlled Comparator Response for Glitch Immunity @ 33.A Max Supply Current Over Temp. Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX8213ACPE OC to +70C 16 Plastic DIP MAX8213BCPE 0C to +70C 16 Plastic DIP Ordering information continued on last page. Typical Operating Circuit 6 CELL STAGK I 1% = Nt 215k - BATT DEAD Oi% _|-_ AAAXLAA MAX8214 IN2 OuTe COW VOLTS TOP VIEW oi , | IN3+ 150k, OUTS veer [a] He] vo ait IN: a FULL CHARGE INt [2] AAAXIAA [15] MS 221k, 0.1% = ute wos] Maxeoid fa) vn 35k ours IN3+ [| Ha] oure LITHIUM 0.1% IN4- BICRUE an BATTERY : na- [5 fia] ous = = DIN Nae [6] iia] outa = DOUT; Ind- [7 | 1] BOUT a oN [8 9] GND [et o a 1.25V VREF REFERENCE DIP/SO MAAXIAA Maxim integrated Products Call toll free 1-800-998-8800 for free samples or literature. PLESXVW/ELCSXUWMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring ABSOLUTE MAXIMUM RATINGS VDD tO GND 2.0.00. eee -0.3V, +12V Digital Input Voltage toGND ............ -0.3V, (VoD + 0.3V) VREFtoGND ......... 0. cece eee -0.3V, (VDD + 0.3V) VouTto GND ..... 0.6. eee -0.3V, (VpD + 0.3V) Continuous Power Dissipation (Ta = +70C) Plastic DIP (derate 10.53mW/C above +70C) ...... 842mW SO (derate 8.70mW/"C above +70C) ............. 696mWw CERDIP (derate 10.00mW/C above +70C) ........ 800mwW Operating Temperature Ranges: MAX821__C__ MAX821__F__ MAX821__MJE -58C to +125C -65C to +165C Storage Temperature Range Lead Temperature (soldering, 10sec) bette +300C 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 (Vpp = 5V, GND = OV, Ta = +25C, unless otherwise noted.) PARAMETER | CONDITIONS MIN TYP MAX | UNITS POWER SUPPLY Positive Supply Voltage MAK621_ a7 4 Range (Note 1) TA = TMIN to TMAX MAG ae 2.85 11 V Positive Supply Current TA = TMIN to TMAX 16 33 HA REFERENCE OUTPUT Ta = 425C MAX821_A -0.75 0.75 MAX821_B -1.50 1.50 MAX821_AC -1.00 1.00 Reference Variation MAX821_BC 72.00 2.00 % Referred to 1.25V Ta = Tanto Tuax MAX821_AE -1,25 1.25 MAX821_BE -2,.50 2.50 MAX821_AM -1.50 1.50 MAX821_BM -3.00 3.00 Reference Load TA = TMIN to TMAX 40 HA Load Regulation 10 pV/pA Line Regulation 0.005 SN Output Tempco 15 ppm/C COMPARATOR INPUTS Ta = 425C MAX821_A -0.90 0.90 MAX821_B -1.50 1.50 MAX821_AC -1.00 1.00 Comparators IN1-IN4 ; MAX821_BC -2.00 2.00 Trip Level with Respect VIN decreasing % MAX821_AM -1.50 1.50 MAX821_BM -3.00 3.00 MAXIMFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring ELECTRICAL CHARACTERISTICS (continued) (VoD = 5V, GND = OV, Ta = +25C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX | UNITS | MAX821_AC -1.00 1.00 MAX821_BC -2.00 2.00 Comparators IN2-IN4 MAX821_AE -1.25 1.25 3 orp Lev wath Respect Vin decreasing Ta = TMIN to TMAX MAX821_BE 250 250 % MAX821_AM | -1.50 1.50 I | MAX821_BM | -2.50 2.50 : | -MAX821_A 15 15 Ta = +25C | MAX821_B 25 25 | maxe21_Ac 2.0 2.0 Comparator DIN MAX821_BC -3.0 3.0 Trip Level with VIN decreasing % Respect to 1.25V MAX821_AE -2.5 2.5 TA = TmIN to TMAX MAX821_BE -3.0 3.0 MAX821_AM -3.0 3.0 MAX821_BM -3.5 3.5 Compara NINA i 17 we | my Hysteresis Tempco 30 | pvfC Input Bias Current 15 10 nA Input Voltage Change for O41 my Complete Output Change | | upper timit Voo - 2V pout Common-Mode IN3, IN4 (Note 3) = 20 3 BE V COMPARATOR OUTPUTS Vop = 5Y, ISiInk = 2mA TL 0.11 0.30 Voo = 5V, Isink = 5mA 0.28 0.75 Voltage Output Low Ta = TMIN to TMAX Vop = 1.6V. ISInK = 0.2mA 004 0.30 Vv Vopb = 1.0V, ISINK = 0.1mA 0.10 Voltage Output High Vob = 5V; ISOURCE = 1MA (MAX8214) Vop-0.4 Vpp-0.15 vi | Leakage Current Off state (MAX8213) [ 1.0 pA MODE SELECT INPUT Leakage Current [- ma 1.0 | HA DYNAMIC SPECIFICATIONS Comparator Response 30mV overdrive 20 ys Note 1: For lower voltage range operation, see Figure 22. Note 2: Each of the comparators has one input tied to VREF. Note 3: Vee equals approximately 0.45V at +250C. The temperature coefficient of Vae equals approximately -2.2mv/C. MA AXIAA PLESXVW/ELZ8XVWMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring COMPARATOR INPUT BIAS CURRENT vs. SUPPLY VOLTAGE 20 Vint = 2V Vin- = REF Ta= 425C INPUT BIAS CURRENT (nA) Ss 0 12 3 4 5 6 7 8 9 10 Vop (V) REFERENCE VOLTAGE vs. TEMPERATURE 1.25172 1.251 Vop = 5V REFERENCE LOAD = OmA 1.25064 1 VREF (V) 1.24902 1 55 -35 -15 5 TEMPERATURE (C) 25 45 65 85 105 125 SUPPLY CURRENT vs. SUPPLY VOLTAGE Ta= Ta=+125C Ip (HA) 123 4 5 6 7 8 9 10 11 12 Vpo (V) INPUT BIAS CURRENT (nA) = uw wo oe > Vou (V} COMPARATOR INPUT BIAS CURRENT vs. TEMPERATURE Vint = 2V Vin- = REF Vop = 5V 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) REFERENCE VOLTAGE vs. REFERENCE SOURCE CURRENT Vese A= +125C 1.250 1.248 1.246 1.244 1.242 1.240 1.238 1.236 1.234 0 25450 75 100 125 150 REFERENCE SOURCE CURRENT (11A) OUTPUT VOLTAGE vs. OUTPUT SINK CURRENT Ta=4125C | Ta=425C | Ta=-55C 1.50 1.25 1.00 0.75 0.50 0.25 0 25 8 11 14:17 20 23 26 29 32 35 OUTPUT SINK CURRENT (mA) 1.2486 = uy 1.2485 ac = 4.2484 Typical Operating Characteristics REFERENCE VOLTAGE vs. SUPPLY VOLTAGE 1.2490 1.2489 1.2488 1.2487 Ta= REFERENCE LOAD = OmA 1.2483 1.2482 1,2481 4.2480 253 4 5 6 7 8 9 0 12 Von {V) REFERENCE VOLTAGE vs. SUPPLY VOLTAGE 1.249 1.287 1.245 = wp 1.248 z Ta=-55C REFERENCE LOAD = OmA 1.241 1.239 1.237 18 20 22 24 26 28 30 32 Vpo () MAX8214 Vo - Von vs. OUTPUT SOURCE CURRENT 1.75 Tas+ Ta=425C Ta=-55C 1.50 1.25 = 1.00 = 2 075 => 0.50 0.25 0 01 23 45 6 7 8 9 10 1112 13 OUTPUT SOURCE CURRENT (mA) MAXIMFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring Typical Operating Characteristics (continued) OUTPUT VOLTAGE vs. SUPPLY VOLTAGE COMPARATOR RESPONSE (see Figure 23.) WITH 30mV OVERDRIVE SUPPLY VOLTAGE COMP [eeeeiemmenaaed OUTPUT COMP fi INPUT QUTPUT VOLTAGE COMPARATOR RESPONSE COMPARATOR RESPONSE WITH 50mV OVERDRIVE WITH 100m OVERDRIVE COMP OUTPUT COMP INPUT Pin Description PIN NAME FUNCTION 1 VREF Output of the Internal 1.25V Reference 23 IN1. IN2 Noninverting Inputs of Comparators 1 and 2. The inverting inputs of these comparators are tied to the ' ' internal reference. Noninverting Inputs of Comparators 3 and 4. The inverting inputs of these comparators are available 4.6 INS+, IN4+ external to the device. po 5,7 IN3-, IN4- inverting inputs of Comparators 3 and 4 Noninverting Input of the Auxiliary Comparator. The trip-level accuracy of this comparator is less 8 DIN than that of the other four comparators; otherwise it is identical. Its inverting input is tied to the inter- nal reference. 9 GND Power-Supply Ground MAXIAA PLESXVW/E LCSXVNMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring Pin Description (continued) | PIN NAME FUNCTION 10 DOUT Output of the Auxiliary Comparator S % Sure, Ours: Outputs of the Four High-Accuracy Comparators Mode Select. Input determining the polarity of the signal appearing at OUT1 and OUT2. A high level 15 MS inverts the comparator outputs, whereas a low level does not. Connecting MS to VREF causes OUT2 to be inverted, while OUT7 is not. 16 VoD Power-Supply Positive Voltage Input Detailed Description MS Block Diagram IN3+ IN4+ IN4- DINJ Figure 1. MAX8213/MAX8214 Block Diagram The MAX8213/MAX8214 contain five comparators. The comparator with its output labeled DOUT is distinguisned from the other four in that its trip point is not as accurate. The inverting inputs of this comparator, as well as those of comparators 1 and 2, are connected to the internal 1.25V reference (see Figure 1). Both inputs of comparators 3 and 4 are available external to these devices, allowing threshold levels to be set by the user at either the inverting or noninverting inputs. The MAX8213's comparators have open-drain outputs, and the outputs of the MAX8214 are actively driven both high and low: this is the only difference between the two devices. Thus the MAX8213 is suitable for driving LEDs or for circuits where the outputs need to be wire-ORed (see the Typical Applications section). Among other applica- tions, the MAX8214 comparator outputs are useful for driving both TTL and CMOS digital circuitry. The Mode Select (MS) pin determines the polarity of OUT1 and OUT2. Table 1 shows the state of the comparator outputs in the three possible modes of operation when the noninvert- ing input voltage exceeds that of the inverting input. If the inverting input exceeds the noninverting input, then invert the outputs shown in the table. When operating in the mode where MS is connected to the VREF pin, OUT1 is not inverted, while OUT2 is inverted. This mode of operation is useful when constructing window com- parator circuits (see the Typical Applications section). Basic Overvoltage and Undervoltage Detection Circuits When the valtage on one comparator input is at or near the voltage on the other input, ambient noise generally causes the comparator output to oscillate. The most common way to eliminate this problem is through hysteresis. When the two comparator input voltages are equal, hysteresis causes one comparator input voltage to move quickly past MAXIMFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring TABLE 1. MAX8213/MAX8214 Comparator Outputs when Noninverting Input Exceeds Inverting Input MS OUT1 OUT2 OUT3 OUT4 DOUT LOW 1 1 1 1 1 HIGH 0 0 1 1 1 VREF 1 0 1 1 1 +5V as T O41 pF +Vs1 INt Vop OUT! }- MAAXIIA T MAX8213/ - MAX8214 ia IN2 OUT2 f +Vs3 ee IN3(+ OR -) OUT3 F Ws4 ESE | IN4(+0R -} ouT4 - Figure 2. Alternative Means for Reducing impedance Level Seen at Inputs MAAXIAA MAX8213/ MAX8214 t 0.AmF Figure 3. Additional Supply- Voltage Filtering MAMXILAA the other, thus taking the input out of the region where oscillation occurs. Standard comparators require that hysteresis be added through the use of external resistors; these resistors are not necessary when using the MAX8213 and MAX8214 because hysteresis is built into these devices. The addition of hysteresis to a comparator creates two trip points, one for the input voltage rising and one for the input voltage falling. When the voltage at a MAX8213/ MAX8214 noninverting input falls, the threshold at which the compa- rator switches equals the voltage on the comparators invert- ing input. However, when the voltage at the noninverting input rises, the threshold equals the voltage at the inverting input plus the amount of hysteresis voltage built into the part. The trip pointis somewhat more accurate when the hysteresis voltage is not part of the threshold voltage, because the tolerance of the hysteresis specification adds to that of the trip point (and to the tolerance of the reference, if used). Ifa comparators inverting input is used to monitor a signal, then, when the input voltage falls, the threshold equals the voltage on the noninverting input minus the hysteresis voltage; when the inputvoltage rises, the threshold simply equals the voltage on the noninverting input. One input of each comparator must be within the Input Common-Mode Range (see the Electrical Characteristics) when a comparison is made (i.., the threshold voltage must be within this range). Any voltage is allowable on the other input prior to the comparison, as long as this voltage does not violate the input absolute maximum rating. Only comparators 3 and 4 are specified for this parameter because the thresh- old level of the other comparators is preset to the internal reference voltage. Immunity to high-speed glitches has been provided by controlling the response time of the comparators. The 5us to 20us response time ensures that very fast glitches are ignored, Application Hints Eliminating Output Oscillation Although hysteresis is built into these devices, output oscillation problems are still possible. One way these problems occur is when the output of a comparator couples back to its inverting input through stray board capacitance. Make sure the board trace leading from a comparator output does not pass near its inverting input (or vice versa). Also, reducing the amount of resistance connected to the comparator inputs reduces the suscep- tibility of the inputs to picking up output signals. In most cases, using input resistor values on the order of 100kQ creates no problem. Since use of lower resistor values increases the supply current, another approach is to bypass the input resistors as shown in Figure 2, although this slows the circuit's response. VLZSXVW/E L2SXUNMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring I vrer = Von RIA N81 2) Nt ws (2 ei MAXIM - pon = MAX8214 4 +V2 3 IN2 OUT! F R2B : our2 [13_ R3A = r +Vs3 IN3+ 12 Ena ; ours | = >] IN3- 11 outs J R4A 6 +54 IN4+ ere 7 1 INd- 8 co DIN GND Ts +5V Our lis es Uvrer Yoo Asi Aw- 2 Ms st 3 Nt = aa Mey MAXUM wise AA La yy MANETS ras RIA ~ | 4 +Vs3 IN3 out! rao 5 = $77 INB- ouT2 RdA p ee: | IN4s ouT3 RB? | 7 11 = * IN4- OUT4 8 e{ON ow 19 Figure 4. Quad Undervoitage Detector Oscillation problems can also occur due to brief refer- ence-voltage variation caused by abrupt supply-voltage changes. At minimum, a0.1LF supply bypass capacitor should be used. This bypassing can be supplemented by adding a 1kQ resistor (or larger if necessary, bearing in mind the device supply current) as pictured in Figure 3. When the voltage supplying the part is also the one being monitored, this 1kQ resistor is sometimes required. See the section Monitoring the Voltage Powering the MAX8213/MAX8214. In addition to decoupling the power supply, bypass VREF to GND if supply-voltage variations are severe. The optimal bypass value typically lies between 0.01pF to 1pF. When the MAX8213 is required to sink larger currents (i.., when smaller value pull-up resistors are used), oscillation problems are more likely to occur. To minimize power consumption and optimize stability, use the largest value pull-up resistor feasible for the output drive re- quired. When lower value pull-up resistors are used, lower values for the resistors connected to the inputs can help alleviate oscillation problems. Unused Inputs When comparators within the MAX8213/MAX8214 are not used, tie the unused inputs to either the positive supply or ground. This prevents noise generation due to the comparator outputs switching from one logic state to another when noise is present at the inputs. When either 8 Figure 5. Quad Undervoitage Detector with LED Indicators comparator 3 or 4 is not used, tie one input of the comparator to the positive rail and the other to ground. Tying both inputs of the same comparator to the same potential may still allow input noise to cause unwanted output switching. Typical Applications Undervoitage Detectors Both the MAX8213 and MAX8214 can be configured to detect when a monitored voltage has dropped below a particular level. In many applications, the MAX8214 is easier to use than the MAX8213 because it requires no external components at its outputs (Figure 4). However, the open-drain outputs of the MAX8213 make it more amenable to certain situations, such as when turning on LEDs during an undervoltage condition (see Figure 5). A low at a comparator output indicates an undervoltage condition and causes the associated LED to light. An alternative way to connect the LEDs is shown in Figure 6: this inverts the operation of the LEDs, making the circuit an overvoltage detector. Since LEDs often require sev- eral milliamps, it may be necessary to follow some of the suggestions listed in the Application Hints section to avoid oscillation problems. Figure 7 shows the MAX8213 outputs wired together so that a low output signal occurs when any of the four monitored voltages goes below a preset value. MAXIMFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring +5V a Tie O4MF Wvrer Vp RIA +Vs1 21 int ws [2 mB MAXIM - R2A = MAX8213 +Vg2 IN2 Our 28 RIA ~ Fe 4 IN3+ ouT2 R3B L |5) ng. RAA +54 I nas ours RAB] 1 | IN4- 1" yon guy ours ; } 13 : ig OME VREF Yop RIA Net 2 wn ws g RIB MNMAXLM ~ i MAX6213 Rea = 3 14 +Vs2 IN2 oun RIB OE , ran = ouT2 +V53 4 IN3+ 42 3 8 5 ouT3 = Ti oura |" RAA 6 4Vg4. AW IN4s 2 | i IN4- DIN GND t9 Figure 6. Overvoltage Detection by Using Alternative LED Connection Figure 8 illustrates the operation of these three un- dervoltage detection circuits. The direction of the input voltage determines at which of two trip points the com- parator switches. Thus the diagram includes arrows that indicate whether the input voltage is rising or falling. The formulas allow the determination of trip- point voltages for specified resistors, and facilitate the calculation of the appropriate resistor ratios for partic- ular trip points. The MAX8213/MAX8214 comparator outputs correctly display a low level down to a 0.8V typical supply volt- age. This is useful in undervoltage applications where the monitored power supply is also the supply con- nected to the VDD pin. See the section Monitoring the Voltage Powering the MAX8213/MAX8214. Overvoltage Detectors Figure 9's circuit allows the detection of overvoltage conditions. Thus, when a particular input voltage rises above a preset trip level, the corresponding compara- tor output goes low. The means of driving LEDs for undervoltage detectors, shown in Figures 6 and 7, also apply to overvoltage detectors constructed using MAX8213s. The waveforms and formulas of Figure 10 apply to MAX8213 as well as MAX8214 circuits. MAMXLAA Figure 7. Single LED Indicating Undervoltage Condition on Any of Four Channels OUTPUT VOLTAGE VALUES: INPUT VOLTAGE VIRIP1 --------K-- VTRIPA = VTRIP2 = Vtrip2 - I 1 GND --------- l Voo ee GND TQ DETERMINE THE TRIP VOLTAGES FROM PARTICULAR RESISTOR RA VIH (1 + | RA (WH + Vwvsr) [ + | fore TQ CALCULATE THE REQUIRED RESISTOR RATIOS FOR PARTICULAR TRIP VOLTAGES: RA _ ViRIPt RB TH RA Vine RB VTH + VHYST NOTE: VHS THE VOLTAGE ON THE INVERTING PIN OF EACH COMPARATOR. 7 RA ; | vs ( + 73 | Figure 8. Undervoltage Detector Waveforms and Formulas PLZSXVW/ELZSXVUNMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring +6V ' ip OL | vrer 00 RIA +Vs1 w 2 IN1 MS 15 RIB rat |, MAXG214 4 +82 ~W IN2 OuT1;- ras 3 + QUT2 F P) ING 12 R3A 5 OUT3 -} V3 W\4 IN3- 1" ga 5 OUT4 - = IN4+ R4A 7 +Vs4 IN4- A4B 8 = DIN GND - La Vv pa 6 O.1pF x vreF = V0 2 OotprT | | 7 RA - ws MAXLZA ) Ws ww 2) int MAX8213- gyri | 14 R2 3} ino our2}43 OUTPUT a ~ 4) nae 5] IN3- [4 Figure 11. Window Detector (Vs) OUTPUT VOLTAGE FOR COMPARATORS 1, 2, & THE FOR COMPARATORS 1, 2, THE AUXILARY COMPARATOR, TO AUXILARY COMPARATOR, TO DETERMINE THE TRIP VOLTAGES CALCULATE THE REQUIRED FROM PARTICULAR RESISTOR RESISTOR RATIOS FOR PARTICULAR aA TRIP 'VOLTAGES: IP Vrrip1 = VTH ( i RB Vm -1 RA RA __Vrne__, Wrip2 = (vm + Versr) ( + 33] RB VrH-+ Vuyst FOR COMPARATORS 3 & 4, TO ncurses, GLEN HE FROM PARTICULAR RESISTOR RESISTOR RATIOS FOR PARTICULAR VALUES: wa aA Viney Vieiet = (vm - Vist) ( + | RB WH-VaysT RA _ Vine _ Virtr2 = VTH ( + | RB VI NOTE: Vii IS THE VOLTAGE ON THE INVERTING PINS OF COMPARATORS 1 AND 2, AND IS THE VOLTAGE ON THE NONINVERTING PINS OF COMPARATORS 3 AND 4. Virip4 . COMP. ape a SE INPUT VOLTAGE (Vs) ( + a" | VIRIP2 ---27<~----- don-n on bom R ron * COMPT apy \- ' (Vavsr #3 ( hi i] GND --4-------- 4 - + 1 ' I Yoo 1 OUTPUT VOLTAGE GND Le TO DETERMINE THE TRIP VOLTAGES TO CALCULATE THE REQUIRED FROM PARTICULAR RESISTOR VALUES: RESISTOR RATIOS FOR PARTICULAR TRIP VOLTAGES: V = Vi 14+ _R3_ TRIPT = VTHI TT + Bo po R2_ Wines (VTH1) { RI Vinips (VtH2) 2 _ Mone (Vt + VST) Ri Virip2 (VTH2 + VHYST2) R3_ Virus (Vrript Vii) Ri Vinipa (V2) Vira = (vr + Varsre) ( + es *) R3_ Viripa (Vinipe - Wt VHysT1) Ri Wanip2 (WrH2 + Vista) Virie2 = (vet +1 We Virip3 = VTH2 ( ae NOTE: Viw1 AND Vie ARE THE VOLTAGES ON THE INVERTING INPUTS OF COMPARATOR 1 AND COMPARATOR 2, RESPECTIVELY (BOTH ARE EQUAL TO THE REFERENCE VOLTAGE IN THIS CASE). Figure 10. Overvoltage Detector Waveforms and Formulas Figure 12. Window Detector Waveforms and Formulas MAAXILAAFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring Window Detectors The circuit pictured in Figure 11 illustrates how two comparators can be configured to detect when a voltage level is between two trip voltages. The combination of comparator 1, which is configured as an undervolitage detector, and comparator 2, which is set up as an over- voltage detector, creates the voltage window. Note that the input voltage curve of Figure 12 is different than those shown for the undervoltage and overvoltage circuits. This curve shows input voltage transitions from inside to out- side the window (left part of curve) and from outside to inside the window (right part of curve); the curve below shows the output voltage waveform for these two situa- tions. For values of R4 below about 10k, output oscillation may occur unless VREF is bypassed with 0.01pF. Monitoring Negative Voltages Undervoltage, overvoltage, and window-detector circuits can be made to monitor negative voltages, as shown in Figures 13, 15, and 17. This technique balances the pull-up effect of the reference with the pull-down effect of the negative voltage being monitored. It is possible that the comparator inputs will go more than 0.3V below ground when using these circuits. Despite the fact that this violates one of the device absolute maximum ratings, itis not a problem if the current that flows through the input resistor is limited to 1_mA. When the comparator inputs are taken below ground, the input clamps at approximately -0.3V; thus, when the quantity |-Vs + 0.31 is divided by the input resistor, the quotient should be less than 1mA. When building these circuits, remember that the reference output current capability is limited (see the Electrical Characteristics). Figure 13 shows a dual negative un- dervoltage detector, Figure 15 a dual negative overvolt- age detector, and Figure 17 a negative voltage window detector. Microprocessor Reset Circuit with Time Delay It is often necessary to reset a microprocessor when its supply voltage drops below a certain level. The circuit pictured in Figure 19 generates a low output when the monitored voltage drops below the threshold set by R1 and R2. Additionally, this output remains low for 200ms after the supply voltage goes above the threshold. Mi- croprocessor reset circuits typically include this feature because it gives the microprocessor time to be fully reset after power has been restored, and allows any capacitors in associated circuitry time to charge. The waveforms and formulas for this cifcuit are shown in Figure 20. Although the function for the time delay appears negative, the calculated time delay will be positive since the natural log will have a negative value. +5V O.1MF 16 t 1 15 qvrep = 00 MS 4 IN RIBS R2B MAXIMA M, 12 SY MAKB2T ah? 4 " a INS uray 1A vst 5 ing- 6 +J IN4+ ROA 1 -Vs2 WW IN4- oN eno aL ee) Figure 13. Dual Negative Undervoltage Detector INPUT VOLTAGE OUTPUT VOLTAGE ViRIP2 = -VHYST RA Virip1 =VREF 5 RB TO DETERMINE THE TRIP VOLTAGES FROM PARTICULAR RESISTOR VALUES: 14 f8 RB ViriP1 .---------- 420 -- NL ------- +++, ! [ves | VtalP2 <7 ------ peeeee nee e eee ye 1 TRIP VOLTAGES: RA WRI RA RB VREF VREF =~ RB RA _ -Virip2 Vyst RB Vuyst + VREF TO CALCULATE THE REQUIRED RESISTOR RATIOS FOR PARTICULAR 1458 RB Figure 14. Dual Negative Undervoltage Detector Waveforms and Formulas " MAXIMA PLESXUVW/ELZ8XUWMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring +5V O.AuF + 16 = 1 VREF Vo ws} 2) int RIBS R2B | _ Maram , lino MAX8214 RIA Vet AV ings 5) ing. ours 2. Vg eh inn outa 7 , TIN 8 o DIN GND + t9 5V * OApF E 16 = 1 vrer VOD ws 21 int Res maxim 3} iyo MAX8213 41 Ng 5 INS- ours } 2 se R2 8} Inde oura OUTPUT = 7) INa- R3 8} DIN GND ['3 Vg ~ Figure 15. Dual Negative Overvoitage Detector VirIPt--= INPUT VOLTAGE (Vs) Vinip2--------->x<-- Vop: OUTPUT VOLTAGE GND TO DETERMINE THE TRIP VOLTAGES. FROM PARTICULAR RESISTOR VALUES: RA RA ViriPt = VHYST ( + a VREF 7B = RA Virip2 = VREF FB TQ CALCULATE THE REQUIRED RESISTOR RATIOS FOR PARTICULAR TRIP VOLTAGES: RA _ Viript VHysT RB Vuyst VREF RA ViRip2 RB VREF GND -------------------------------- Vint Soon : compa nl J vevst? qTRIpP2-- | KW -------------------54-- - R3 INPUT VOLTAGE 143 _ Vs R1+R2 COMP 3 ViRIP3 4 - . VrRiPa Vywsty as ' [+ At ) Vop OUTPUT VOLTAGE GND TO DETERMINE THE TRIP VOLTAGES FROM TO CALCULATE THE REQUIRED PARTICULAR RESISTOR VALUES: RESISTOR RATIOS FOR R3 R3 PARTICULAR TRIP VOLTAGES: Virlpt = VTH4 1+ar Re Ro | Riek +Re +R2 RS Virier Vina Viap2= (vm - Vast) 148 RY + RQ Vina VREF Ri +R2 vrer 2 R3___ Virip2 VTHa + VHvsT4 R1+R2 R1+R2 0 VtHaVuysta VREF Virip3 = (Vis + Vist ) i+ a] Rt _ tua + VaysTs ~ VREF R2+R3 R2+R3 Vrrip3 VrH3 -VHysT3 ~ VREF _ Rt Rt __VtH3- VREF R2 +R, R2+R R2+R3 Vtripa V Vipipa = VHB ( + fi *} VREF es * TRIPA NTH NOTE: Vii IS THE VOLTAGE ON THE INVERTING INPUT OF COMPARATOR 3. VtHa IS THE VOLTAGE ON THE NONINVERTING INPUT OF COMPARATOR 4. IN THIS CASE, RS _ vper. VH3 = VTHa = Re +P5 Figure 16. Dual Negative Overvoitage Detector Waveforms and Formulas 12 Figure 18. Negative Voltage Window Detector Waveforms and Formulas MAXIMAFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring +5V na 16 O41 pF LT 1 Voo 15 vReF MS} R = 680k +VS 2 Nt Ro MAXIM 3) yy MAKE213 oy |14 RI A i + ING 5} ing. 18) inde 7 IN4- 8 10 ___ DIN cup DOT RESET tg CT wr +5\, R3 S 2 16 Ot ar 1 VoD 5 VREF Mse4 R = 680k 2 IN| AAAXIAA Re MAX8213 3 14 | IN2 OuT1 R L Ll ina, 5} 3. LFF nas 7 ina 8 10 DIN @ND DOUT| RESET = 9 C T ip rigure 19. Microprocessor Reset Circuit with 200ms Time elay ViRIP2---- INPUT VOLTAGE Vint GND---------- outpuT = Yoo VOLTAGE (OUT!) ~~ GND Vop ate OUTPUT VOLTAGE (DOUT) GND TO DETERMINE THE TRIP VOLTAGES TO CALCULATE THE REQUIRED FROM PARTICULAR RESISTOR RESISTOR RATIOS FOR PARTICULAR 5 mo TRIP VOLTAGE: _ R2 R2_ Vin Vrapi=VtH] 1+ pe . RI Va Virip2= (va + Vast) [ + ri R2_ Varo R1 Vi4+ Vayst MH toy=-F0 a t NOTE: Vu IS THE VOLTAGE AT THE INVERTING PIN OF THE TWO COMPARATORS. IN THIS CASE IT IS EQUAL TO THE INTERNAL REFERENCE VOLTAGE. Figure 20. Microprocessor Reset with Time Delay Waveforms and Formulas MA MXLAA Figure 21. Microprocessor Reset Circuit Monitoring Its Own Supply Voltage Monitoring the Voltage Powering the MAX8213/MAX8214 Itis often desirable to monitor the voltage that is powering the MAX8213 and MAX8214. In general, when operated this way, these circuits are more prone to output oscilla- tion. Of the application hints suggesting how to eliminate oscillation problems, most important in this case is the addition of the series supply resistor (see the Application Hints section). In general, reducing input resistor values and output current levels minimizes the possibility of oscillations. Sometimes a reference bypass capacitor may also be needed. Many of these circuits have no oscillation problems and do not require a series supply resistor (R3) or reference bypass capacitor. Pictured in Figure 21 is the microprocessor reset circuit of Figure 19, but with the supply being monitored also powering the MAX8213. The waveforms and equations of Figure 20 also apply to this circuit. The MAX8213/MAX8214 comparator outputs correctly display a low level down to a 0.8V typical supply voltage. This is useful in undervoltage applications where the monitored power supply is also the supply connected to the VDD pin. PLESXVW/ELZSXUWNMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring SUPPLY VOLTAGE = 1k T O.AyF vReF VoD R3 R2 MAAXLA 60k MAX8213 IN3+ IN3- OUT3 RA 40k ms VS. 15k 10k 2k = O.1pF Voo MS MAXIMA MAX8213 ourt VS a 180k Figure 22. Undervoltage Monitoring with Supplies as Low as 2.25V for Full Military Temperature Range. R3, R4 divide the ref- erence to create 0.5V at IN3-. R71, R2 are used to set the trip level. This current will trip when supply voltage reduces to F2 osy(t + rd Auxiliary Comparator The auxiliary comparator is noninverting and can be used in microprocessor reset circuits such as those shown in Figures 19 and 21. Alternatively it can be used to monitor positive voltage levels, but it is less accurate than the other four comparators. Lower Supply Voltage Operation The lower supply voltage limit is controlled by the mini- mum voltage required for the internal reference voltage generator and by the common-mode range of the com- parators. Cold temperature in both cases sets the lower limit. The reference voltage is usable to 2.1V for commercial temperature, and to 2.25V for extended and military temperature range devices. The common-mode range required for the comparators is 2VBE from the supply voltage. 2VBE is roughly 1.55V at -55C. Comparators 1, 2, and DIN require at least 2.85V for military temperature range operation, since one input of the comparator is tied to the reference voltage. However, comparators 3 and 4 have uncommitted inputs and by comparing input volt- ages to a fraction of the reference voltage (for example 40%, as shown in Figure 22), operation down to 2.25V is possible for the military temperature range and 2.1V for the commercial temperature range. 14 Figure 23. Undervoltage Monitoring for 3.3V Supplies. Circuit trips at 3.125V. After OUT1 goes low, the "0" level is maintained typically down to 0.8V. See Typical Operating Characteristics section. _ Ordering Information (continued) PART TEMP. RANGE PIN-PACKAGE MAX8213ACSE 0C to +70C 16 Narrow SO MAX8213BCSE 0C to +70C 16 Narrow SO MAX8213BC/D 0C to +70C Dice * MAX8213AEPE -40C to +85C 16 Plastic DIP MAX8213BEPE -40C to +85C 16 Plastic DIP MAX8213AESE -40C to +85C 16 Narrow SO MAX8213BESE -40C to +85C 16 Narrow SO MAX8213AMJE -55C to +125C 16 CERDIP MAX8213BMJE -68C to +125C 16 CERDIP MAX8214ACPE 0C to +70C 16 Plastic DIP MAX8214BCPE 0C to +70C 16 Plastic DIP MAX8214ACSE 0C to +70C 16 Narrow SO MAX8214BCSE 0C to +70C 16 Narrow SO MAX8214BC/D OC to +70C Dice * MAX8214AEPE -40C to +85C 16 Plastic DIP MAX8214BEPE -40C to +85C 16 Plastic DIP MAX8214AESE -40C to +85C 16 Narrow SO MAX8214BESE -40C to +85C 16 Narrow SO MAX8214AMJE -55C to +125C 16 CERDIP MAX8214BMJE -55C to +125C 16 CERDIP * Dice are specified at Ta = +25C. MA AXLAAFive Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring Chip Topography MAX8213/MAX8214 (1. ares mm) MAX8213/MAX8214 TRANSISTOR COUNT: 352; SUBSTRATE CONNECTED TO Vpp. MAAXLAA 15 PELESXVW/ELZSXUWMAX8213/MAX8214 Five Universal Voltage Monitors - Complete Microprocessor Voltage Monitoring Package Information (continued) 0.780 MAX TaBr2| | LEAD #1 280 2 omg T | 0.030 = 0.110 ggy egen 10 F ae 0.025 + 0.015 VUUUUOUU oor = 018 oll 0.300 - 0.320 (7.620 - 6.126) O00 typ _ 0.020 (1.016) (0.508) 0.130 + 0.005 e102 (3302 = 6.127) iyi ar- f = Maoh a 0.020 0.125 {6.506 MIN -+l. fa175) MIN 0.018 = 0.003 +0025 (0457 = 0.076) 0.100 = O10 a =itis O15 (2540 + 0.254) (azss UBS) 16 Lead Plastic DIP B yn = 1385C/W 8) = 65C/W ois - 0.158 bit) = 0.205 0.228 - 0.244 3.810 - 4.013) (4.587 5.207] (5.791 - 6. LEAD ( f 5.207] (5.791 - 6.198) 036 - 0.457) | {1.270} BSC ro 0,385 - 0.304_ (0.381) (9.779 - 10.007) Te 0.586) eae ~ Ae 0.009 0.004 - 0.008 j0.1 78 - 0.229) j0.102 0.203) 16 Lead Small Outline Oj, = 110C/W Byc = 60C/W 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. 16 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 1992 Maxim Integrated Products Printed USA AAAXIAA is a registered trademark of Maxim Integrated Products.