MAX703 MAXIM | Alldatasheet

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19-0130; Rev 1; 4/94 MAXIM Low-Cost uP Supervisory Circuits with Battery Backup General Description Features = ‘The MAX703 and MAX704 microprocessor (uP) super- @ Battery-Backup Power Switching visory circuits reduce the complexity and number of —_@ Precision Supply-Voltage Monitor components required to monitor power-supply and bat- 4.65V (MAX703} tery functions in uP systems. These devices significantly 4.40V {waxros} NX improve system reliability and accuracy compared to _@ 200ms Reset Pulse Width [.} ICs or discrete components. separate ICs or discrete comp: Debounced TTLYCMOS-Compatible Lx) The MAX703/MAX704 are available in 8-pin DIP and SO Manual-Reset Input packages and provide four functions: 200A Quiescent Current 1) An active-low reset during power-up, power- —_@ 50nA Quiescent Current in Battery-Backup Mode > down, and brownout conditions, ¢ Voltage Monitor for Power-Fall or *< 2) Battery-backup switching for CMOS RAM, CMOS Low-Battery Warning NX pPs, or other low-power logic circuitry. @ 8-Pin DIP and SO Packages ° 3) A 1.25V threshold detector for power-fail warning, @ Guaranteed RESET Assertion to Vcc = 1V AA low-battery detection, or for monitoring a power supply other than +5V. 4) An active-low manual-reset input. Ordering Information The MAX703 and MAX704 differ only in their supply-volt- age monitor levels. The MAX703 generates a reset when PART TEMP. RANGE PIN-PACKAGE | the supply drops below 4.65V, while the MAX704 MAX703CPA OC to 470°C 8 Plastic DIP ] generates a reset below 4.4V. MAX703CSA OC to +70°C 8sO Computers MAX703EPA, 40°C to +85°C 8 Plastic DIP | Controllers MAX703ESA -40°C to +85°C 8SO Intelligent Instruments Ordering Information continued on last page. Automotive Systems * Dice are tested at Ts = +25°C only. Critical uP Power Monitoring ** Contact factory for availability and processing to MiL-STD-883. Typical Operating Circuit Pin Configuration UNREGULATED DC REGULATED +5¥ MICROPROCESSOR] TOP VIEW Rt Veo Tour[ ve = _ = =|" a) na vost Gy * |e) vest viiu | woaae ovo vee(2| “iiing [7 RET BATTERY MAX703. ~ m2 ‘MAX7O4 + cno[a] © MAX704—e) WR vBart eu pri [4 5) PO WR guy Vart—el Vor ~ CMOS RAM DIP/SO E pusseurtor MAAXIAA Maxim Integrated Products 1 Call toll free 1-800-998-8800 for free samples or literature.

Low-Cost uP Supervisory Circuits with Battery Backup ‘SF ABSOLUTE MAXIMUM RATINGS (=) Terminal Voltage (with respect to GND) Rate-of-Rise, Vcc, VBATT 100Viis VBATT 0.3V to 6.0V Plastic DIP (derate 9.09mW/"C above +70°C) 727mW < All Other Inputs (Note 1) -0.3V to (Veg + 0.3V) ‘SO (derate 5.88mW/"C above +70°C) 47imw Input Current CERDIP (derate 8.00mW/'C above +70°C) 640mW \\- aa 200mA Operating Temperature Ranges: VBATT 50mA MAX70_C__ 0°C to +70°C GND . 20mA MAX70_E__ -40°C to +85°C ° Output Current MAX70_MJA .. -55°C to +125°C Vout Short-Circuit Protected for up to 10 sec. ‘Storage Temperature Range . -65°C to +160°C © ss Allother Outputs _ ..20mA Lead Temperature (soldering, 10 sec) +300°C N Note 1: Vg is the greater of Vcc and VBATT. The input voltage limits on PFI and MA may be exceeded if the current into these pins < is limited to less than 10mA. Stosses beyond those ited under ‘Absolute Maxirumn Ratings’ may cause permanent damage tothe device. Thase ae stress ratngs ony. and functional Steraton ofthe device at these or any other conditions beyord those indicated nthe operatonalsectons ofthe specricatons (sal mpled, Exposure © SS ering cnt eee aya ce ay

ELECTRICAL CHARACTERISTICS

PARAMETER [ sympous | __—conDmions [MIN TYP MAX | UNITS: Operating Voltage Range Voc. Vaart (Note 2) ° 56 v Supply Current 200380 (Excluding four) ‘surrer “" [SUPPLY in Battery-Backup Vec = ov, 0.05 4.0 A ie texts out) veRIT = Dav " \\VBATT Standby Current ssyevoo> [tassaec | os oe (Note 3) VBATT + 02V Woo-0 68 Voe0 Vour Output jour = Srv pa oe v lout = SOMA _ Veo-05 _Vcc-0.25 Vourin Battery-Backup Mode [| lout = 250A, Voc < Vpart-0.2V VearT- VearT Battery-Switch Threshold [Poweryp | (Wec-WBarT) || Noe Vast a Battery SwitchoverHysteresis | RESET Threshold Vest v MANO RESET Throshoidtysteresis [fm Ga Vec-45 RESET Ot ve MAX70_C, Vcc = 1V. Vcc falling, Vv iput Vollage Vo. | VBATT = OV1sINK = 50nA MAX70_E/M. Vcc = 1.2V, Vcc falling, 03 _ VBATT = OV, Isink = 100A. — 2. . MAXI

Low-Cost .P Supervisory Circuits with Battery Backup ELECTRICAL CHARACTERISTICS (continued) = [| ___Parameren | symeors | conpmions, SS |miN. |_TYP UNITS High a CO | [WaPusewam [af SSS vv | ft | 8 MR to RESET Dolay [wo 20s MAPul-Up Current [soy 00 25000 | [Printers [voces tao Pts fm | | Se [Prtimeutcuren [Pd es | oor | ts fm] Sou Vox IsQuRCE = 800uA Vveots| | ° put Voltage v Vou Isin = 3.2mA, [| oa A Note 2: Either Vcc or VBATT can go to OV if the other is greater than 2.0V. Note 3: *-" = battery-charging current, "+" = battery-discharging current. Typical Operating Characteristics (Voc = +5V, VBATT = +2.8V, Ta = +25°C, unless otherwise noted.) OUTPUT VOLTAGE vs. OUTPUT VOLTAGE vs. ‘RESET OUTPUT VOLTAGE vs.

5.00 LOAD CURRENT 280 LOAD CURRENT SUPPLY VOLTAGE wv

\\ N Ae AN mai Baio on IN nee «LEN + aan some wot NO Pf INA] FEENEY Pat eeN TLE LT fete | peer, Gal 5 as 5 on sor wal ye ea BERNE Be eN ees ie ae SS an Hl own | | 3055 i] eH LEN LEE] ppt Cr T0208 080 tout (mA) tout (mA) ‘0ms/crv MAX703 POWER-FAILCOMPARATOR POWER-FAIL COMPARATOR RESET RESPONSE TIME RESPONSE TIME RESPONSE TIME ee ee ee me yl bo COIS) Se we neh Perr ™ Cat _ , ov | aan OL eT wel OT aaSeeeeee wisiv 5 s09F ae 4-H _ tT | | 1BV ITH, wi aeeens Ee wcafie a] Ew SSaReeEney COE ov a wr LEE finest ea PCC] ow | ETT HE a wm EE aane id Po COPeere errr} Corr aust ces sco MAXIM lg

3 Pin Description

N 4 pe| | Power-Fail Comparator Input. When PF is less than 1.25V, PFO goes low; otherwise PFO remains high. x Connect PFi to GND or Voc when rat used. Figure 1. Block Diagram Figure 2. Timing Diagram

4 AA AXLAA

Low-Cost uP Supervisory Circuits with Battery Backup Detailed Description part vee = RESET Output ] Ss AP's reset input starts the pP in a known state. When- Se ever the pP is in an unknown state, it should be held in or 2) MM a 4 reset. The MAX703/MAX704 assert reset when Vcc is 3 MAX7O 4 . NX low, preventing code-execution errors during power-up. 1 o 2 r ° power-down, or brownout conditions. ‘upsTRATE ® When VBATT 's 2V or more, RESET is always valid, \\ : — irrespective of Voc. On power-up, as VCC rises, RESET remains low. When Vcc exceeds the reset threshold, an > internal timer holds RESET low for a time equal to the reset x pulse width (typically 200ms); after this interval, RESET vour N goes high (Figure 2). Ifa power-fail or brownout condition occurs (i.e. Voc drops below the reset threshold), RESET CONDITION susz_| sass | ° is asserted. As long as Vcc remains below the reset Voc > Reset Threshold Open Closed A threshoid, the internal timer is continually restarted, causing vi ~ 7 H the RESET output to remainlow. Thus, a brownout condition YES SESE Thresnos and Open | Closed that interrupts a previously initiated reset pulse causes an additional 200ms delay from the end of the last interruption. Veo <ResatTrreshold and | Goseg | Open Power-Fall Comparator ESET WESHOLO = 45 MAKE EET HESIOD 4a ANID The PFI input is compared to an internal reference. If PFI Figure 3. Backup-Battery Switchover Block Diagram is less than 1.25V. PFO goes low. The power-fall com- parator can be used as an undervoltage detector to applied to VBATT (Figure 3). During this time, diode D1 signal a failing power supply. In the Typical Operating (between VBATT and the substrate) conducts current Circuit, an external voltage divider at PFI is used to fom VBATT to Vcc if VBATT 2 (Vcc + 0.6V) monitor the unregulated DC voltage from which the regu- When the battery-backup mode is activated, VBATT con- lated +5V supply is derived nects to VouT. In this mode, the substrate connects to The voltage divider can be chosen so the voltage at PF! VBATT and internal circuitry is powered from the battery falls below 1.25V just before the +5V regulator drops out, (Figure 3). Table 1 shows the status of the PFO is then used as an interrupt to prepare the uP for MAX703/MAX704 inputs and outputs in battery-backup power-down. mode. To conserve power, the power-fail comparator is turned When Voc is below, but within, 1V of BATT. the internal off and PFO is forced low when the MAX703/MAX704 switchover comparator draws about 30HA. Once Vcc enter battery-backup mode. drops to more than 1V below VBATT, the internal . switchover comparator shuts off and the supply current Backup-Battery Switchover _{a\\is to less than 1A In the event of a brownout or power failure, it May DE Table 4, Input and Output Status in Bai . ckuy necessary to oreserve tne contents of RAM. With a put put in Battery-Backup Mode backup battery installed at VBATT, the MAX703/MAX704 SIGNAL STATUS automatically switch RAM to backup power when Vcc fails. Disconnected from Vour As long as Voc exceeds the reset threshold, Vcc con- Vou Connected to VBATT through an internal nects to Vour through a 5Q P-channel MOSFET power fou 60a P-channel MOSFET switch switch, Once VCC falls below the reset threshold, RESET Ce Sto Vour Supply curr - goes low and Vcc or VBATT (whichever is higher) VBATT oer oer eee curt is switches to Vout . Note that VBATT switches to VouT < TpAwhen Ver < = (through an 802 switch) only if Vec is below the reset- RESET | Logic low _ a threshold voltage and VBATT is greater than Vcc. When Power-fail comparator is disabled. Vcc exceeds the reset threshold, it is connected to the Logic low MAX703/MAX704 substrate, regardless of the voltage — [MR | Disabled MAXIM _ 5

| | rapidly charges to within a diode drop of Vcc. However. MAXIM suddenly removed and then reapplied with Vcc = 4.75V. Figure 6. RESET Valid to Ground Circuit Backup Power Sources capacitance vaiues (on the order of 0.1 Farad). When _—‘t the reset threshold. ™ Supercap is a registered trademark of Baknor Industnes.

6 AANA

Figure 7. Adding Hysteresis to the Power-Fail Comparator Figure 8, Monitoring a Negative Voltage the same voltage level (regardless of the reset-threshold VCC voltage, and resistors R1 and R2.

Low-Cost .\\P Supervisory Circuits with Battery Backup t Using the Power-Fail Comparator to S Assert Reset IN.__ in addition to asserting reset at the Vcc reset threshoid specified threshold or when Vcc falls below the reset Seq voltage, reset can also be asserted at the PFI input threshold. For additional noise ejection, place a capacitor threshold voltage. Connect PFO to MR to initiate a reset between PFI and GND & buiso when the monitored supply drops below a user- = Table 3. Maxim uP Supervisory Products be) Nominal Reset” | Watchaot |soex cE lu | Low- Active-| Batt | S Note [Tree Pulse | Timeout’ Battery | Write PowerFail "Reset Watchdos ine “High On. N lumber |Thregnold! width | Period Switch | Protect omparator | Input put | Output Reset Output | (ms) | (sec) : x MAX690A | 465 | 140 | 16 | yes | no yes | no | = no | no | no _| Sweats 465 | *40/agj | 16/acj. | yes | yes [yes | no |" yes | yes | yes yes = | waxeg2a | 240 | 140 [16 | yes | no | yes no | no no | no | no | MAX693A | 440 | 140/ad | 1é/ad) | yes | yes yes so | yes yes | yes | yes [[maxeae | aaj. | 5/ad, | 16/ad), | yes | no] yes | no tyes] yes [yes | yes [Maxeo7 adj. | 39/ad, | 16/adj. | no | yes | yes | no | yes | yes | yes | no |_Max700 | 4.65/ad) { 200 | NA | no | ro | 70 yes no no_| yes | no [max7os_| 465 | 140 NA yes_| no | yes yes 0 no | mo ro | MAX704_| 440 | 140 | NA | yes | no | yes yes | no no | _n0 | no MAX705 a65_[ wo [16 [no [no | yes yes | yes | ro | no | no [wax7oe |" 440 | 140 [1.6 | no. no_| yes { -yes | yes_[ no | no no | max7o7_[ 465 [140 [NA | no [no [yes [yes | no [no | yes | no _| [-max7oa | 4.40 [140 NA | no no | yes yes | no | no | yes | no MAX791 4.65 140 1 es_| yes es es es__| yes | yes | yes i . a Ce] i “ oe) | Maxi232 | 4.50/4.76 | 250 12m | | yes no no | yes | no | maxi259 | NA_| NA | NA | yes | no | yes | no no | no | 10 t no | __Ordering Information (continued) _____———s Chip Topography PART TEMP.RANGE _PIN-PACKAGE_ a __ GE 77am) MAX704CPA oc to +70°C 8 Plastic oP MAX704CSA_ 0'C 10 +70°C 8so Your Veatt MAX704C/D OCw+70C Dice \\ _ MAX704EPA ~40°C to +85°C 8 Plastic DIP Veo< fal i on f MAX704ESA __ 40°C to +85°C __8SO0 _ i uw ert AcSeyT | | MAx70aMJA 55°C 10 +125°C 8CERDIP™ = a a 065" * Dice are tested at Ta = +25°C only. RRR Ba — wo, (1.651) Contact factory for availabyity and processing to MIL-STD-883 SLT RS ne | area NY al fuinae EliNtes t ono PFI PFO SUBSTRATE MUST BE LEFT UNCONNECTED TRANSISTOR COUNT. 573 Maxim cannot assume responsibilty for use of any circuitry othor than circuitry entroly embodied in a Maxim product. No cxcuit patent licenses are enplied. Maxm resorves the ngnt to change ihe crcuitry and specications without notice at any time

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