19-2440; Rev 2; 10/02 Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay Applications Portable Equipment Features ♦ Monitor System Voltages from 1.6V to 5V ♦ Capacitor-Adjustable Reset Timeout Period ♦ Low Quiescent Current (1.6µA typ) ♦ Three RESET Output Options Push-Pull RESET Push-Pull RESET Open-Drain RESET ♦ Guaranteed Reset Valid to VCC = 1V ♦ Immune to Short VCC Transients ♦ Small 4-Pin SC70, 4-Pin SOT143, and 5-Pin SOT23 Packages ♦ MAX6340 Pin Compatible with LP3470 ♦ MAX6424/MAX6425 Pin Compatible with NCP300–NCP303, MC33464/MC33465, S807/S808/S809, and RN5VD ♦ MAX6426 Pin Compatible with PST92XX Battery-Powered Computers/Controllers Ordering Information Automotive Medical Equipment Intelligent Instruments PART TEMP RANGE MAX6340UK_ _-T -40°C to +125°C 5 SOT23-5 PIN-PACKAGE MAX6421XS_ _-T -40°C to +125°C 4 SC70-4 Embedded Controllers MAX6421US_ _-T -40°C to +125°C 4 SOT143-4 Critical µP Monitoring MAX6422XS_ _-T -40°C to +125°C 4 SC70-4 Set-Top Boxes MAX6422US_ _-T -40°C to +125°C 4 SOT143-4 Computers MAX6423XS_ _-T -40°C to +125°C 4 SC70-4 MAX6423US_ _-T -40°C to +125°C 4 SOT143-4 MAX6424UK_ _-T -40°C to +125°C 5 SOT23-5 MAX6425UK_ _-T -40°C to +125°C 5 SOT23-5 MAX6426UK_ _-T -40°C to +125°C 5 SOT23-5 Pin Configurations TOP VIEW VCC 1 4 RESET (RESET) 3 SRT MAX6421X MAX6422X MAX6423X GND 2 SC70 Note: The MAX6340/MAX6421–MAX6426 are available with factory-trimmed reset thresholds from 1.575V to 5.0V in approximately 0.1V increments. Insert the desired nominal reset threshold suffix (from Table 1) into the blanks. There are 50 standard versions with a required order increment of 2500 pieces. Sample stock is generally held on standard versions only (see Standard Versions Table). Required order increment is 10,000 pieces for nonstandard versions. Contact factory for availability. All devices are available in tape-and-reel only. Typical Operating Circuit appears at end of data sheet. ( ) ARE FOR THE MAX6422 Pin Configurations continued at end of data sheet. Selector Guide appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX6340/MAX6421–MAX6426 General Description The MAX6340/MAX6421–MAX6426 low-power microprocessor supervisor circuits monitor system voltages from 1.6V to 5V. These devices perform a single function: they assert a reset signal whenever the VCC supply voltage falls below its reset threshold. The reset output remains asserted for the reset timeout period after VCC rises above the reset threshold. The reset timeout is externally set by a capacitor to provide more flexibility. The MAX6421/MAX6424 have an active-low, pushpull reset output. The MAX6422 has an active-high, push-pull reset output and the MAX6340/MAX6423/ MAX6425/MAX6426 have an active-low, open-drain reset output. The MAX6421/MAX6422/MAX6423 are offered in 4-pin SC70 or SOT143 packages. The MAX6340/MAX6424/MAX6425/MAX6426 are available in 5-pin SOT23-5 packages. MAX6340/MAX6421–MAX6426 Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (TA = +70°C) 4-Pin SC70 (derate 3.1mW/°C above +70°C) ..............245mW 4-Pin SOT143 (derate 4mW/°C above +70°C).............320mW 5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW Operating Temperature Range .........................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C All Voltages Referenced to GND VCC ........................................................................-0.3V to +6.0V SRT, RESET, RESET (push-pull).................-0.3V to (VCC + 0.3V) RESET (open drain)...............................................-0.3V to +6.0V Input Current (all pins)......................................................±20mA Output Current (RESET, RESET) ......................................±20mA 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 (VCC = 1V to 5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = 5V and TA = +25°C.) (Note 1) PARAMETER SYMBOL Supply Voltage Range VCC Supply Current ICC VCC Reset Threshold Accuracy Hysteresis VTH tRD Reset Timeout Period tRP VSRT Ramp Threshold IRAMP VTH-RAMP RAMP Threshold Hysteresis RESET Output Voltage Low MIN RESET Output Leakage Current, Open-Drain RESET Output Voltage High RESET Output Voltage Low VOH ILKG VOH VOL V 2.5 4.2 1.9 3.4 VCC ≤ 2.0V 1.6 2.5 TA = +25°C VTH - 1.5% VTH + 1.5% TA = -40°C to +125°C VTH - 2.5% VTH + 2.5% VCC falling at 1mV/µs CSRT = 1500pF 3.00 CSRT = 0 µA V 4 x VTH mV 80 µs 4.375 5.75 0.275 ms VSRT = 0 to 0.65V; VCC = 1.6V to 5V 240 nA VCC = 1.6V to 5V (VRAMP rising) 0.65 V 33 mV VCC ≥ 1.0V, ISINK = 50µA 0.3 VCC ≥ 2.7V, ISINK = 1.2mA 0.3 V 0.4 VCC ≥ 1.8V, ISOURCE = 200µA 0.8 x VCC VCC ≥ 2.25V, ISOURCE = 500µA 0.8 x VCC VCC ≥ 4.5V, ISOURCE = 800µA 0.8 x VCC VCC > VTH, reset not asserted V 1.0 VCC ≥ 1.0V, ISOURCE = 1µA 0.8 x VCC VCC ≥ 1.8V, ISOURCE = 150µA 0.8 x VCC VCC ≥ 2.7V, ISOURCE = 500µA 0.8 x VCC VCC ≥ 4.5V, ISOURCE = 800µA 0.8 x VCC 0.3 VCC ≥ 2.7V, ISINK = 1.2mA 0.3 VCC ≥ 4.5V, ISINK = 3.2mA 0.4 _______________________________________________________________________________________ µA V VCC ≥ 1.8V, ISINK = 500µA Note 1: Devices production tested at +25°C. Overtemperature limits are guaranteed by design. 2 UNITS 5.5 VCC ≤ 3.3V VCC ≥ 4.5V, ISINK = 3.2mA RESET Output Voltage High, Push-Pull MAX VCC ≤ 5.0V VRAMP falling threshold VOL TYP 1.0 VHYST VCC to Reset Delay VSRT Ramp Current CONDITIONS V Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay TA = +25°C 2.5 2.0 TA = -40°C 1.5 1.0 1000 100 10 1 4.30 CSRT = 1500pF RESET TIMEOUT PERIOD (ms) 3.0 MAX6421/26 toc02 TA = +125°C 10,000 RESET TIMEOUT PERIOD (ms) SUPPLY CURRENT (µA) MAX6421/26 toc01 4.0 3.5 RESET TIMEOUT PERIOD vs. TEMPERATURE RESET TIMEOUT PERIOD vs. CSRT 4.25 MAX6421/26 toc03 SUPPLY CURRENT vs. SUPPLY VOLTAGE 4.20 4.15 0.5 0 1 2 3 4 5 4.10 0.01 0.1 1 10 -50 1000 100 25 50 75 100 TEMPERATURE (°C) RESET TIMEOUT PERIOD vs. TEMPERATURE MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE VCC TO RESET DELAY vs. TEMPERATURE (VCC FALLING) 400 350 300 125 100 RESET OCCURS ABOVE THE CURVE 75 50 VCC FALLING AT 1mVµs 150 25 250 0 0 50 25 75 100 125 140 130 120 110 100 90 VTH = 2.95V 200 80 0 TEMPERATURE (°C) 200 400 600 800 1000 -50 -25 0 RESET THRESHOLD OVERDRIVE (mV) POWER-UP/POWER-DOWN CHARACTERISTIC RESET 1V/div 100 125 MAX6421/26 toc08 1.006 NORMALIZED RESET THRESHOLD 1V/div 25 75 50 TEMPERATURE (°C) NORMALIZED RESET THRESHOLD vs. TEMPERATURE MAX6421/26 toc07 VTH = 1.6V VCC 125 MAX6421/26 toc06 150 160 VCC TO RESET DELAY (µs) 450 MAX6421/26 toc05 500 175 TRANSIENT DURATION (µs) 550 -25 0 CSRT (nF) CSRT = 0 -50 -25 SUPPLY VOLTAGE (V) 600 RESET TIMEOUT PERIOD (µs) 0.1 0.001 6 MAX6421/26 toc04 0 1.004 1.002 1.000 0.998 0.996 0.994 400µs/div -50 -25 0 25 50 75 100 125 TEMPERATURE (°C) _______________________________________________________________________________________ 3 MAX6340/MAX6421–MAX6426 Typical Operating Characteristics (VCC = 5V, CSRT = 1500pF, TA = +25°C, unless otherwise noted.) MAX6340/MAX6421–MAX6426 Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay Pin Description PIN MAX6340 SOT23 MAX6421 MAX6422 MAX6423 SOT143 SC70 MAX6424 MAX6425 MAX6426 SOT23 SOT23 NAME FUNCTION 1 3 3 5 1 SRT Set Reset Timeout Input. Connect a capacitor between SRT and ground to set the timeout period. Determine the period as follows: tRP = 2.73 ✕ 106 ✕ CSRT + 275µs with tRP in seconds and CSRT in farads. 2 1 2 3 2, 3 GND Ground 3 — — 4 — N.C. Not Internally Connected. Can be connected to GND. 4 2 1 2 5 VCC Supply Voltage and Reset Threshold Monitor Input 5 1 4 — 4 RESET RESET changes from high to low whenever VCC drops below the selected reset threshold voltage. RESET remains low for the reset timeout period after VCC exceeds the reset threshold. RESET RESET changes from low to high whenever VCC drops below the selected reset threshold voltage. RESET remains high for the reset timeout period after VCC exceeds the reset threshold. 4 — — Detailed Description 3.3V Reset Output The reset output is typically connected to the reset input of a µP. A µP’s reset input starts or restarts the µP in a known state. The MAX6340/MAX6421–MAX6426 µP supervisory circuits provide the reset logic to prevent code-execution errors during power-up, power-down, and brownout conditions (see Typical Operating Characteristics). RESET changes from high to low whenever VCC drops below the threshold voltage. Once VCC exceeds the threshold voltage, RESET remains low for the capacitoradjustable reset timeout period. The MAX6422 active-high RESET output is the inverse logic of the active-low RESET output. All device outputs are guaranteed valid for VCC > 1V. The MAX6340/MAX6423/MAX6425/MAX6426 are opendrain RESET outputs. Connect an external pullup resistor to any supply from 0 to 5.5V. Select a resistor value large enough to register a logic low when RESET is asserted and small enough to register a logic high while supplying all input current and leakage paths connected to the RESET line. A 10kΩ to 100kΩ pullup is sufficient in most applications. 4 VCC 5.0V LASER-TRIMMED RESISTORS 10kΩ VREF RESET 5V SYSTEM SRT CSRT RESET TIMEOUT N MAX6340 MAX6423 MAX6425 MAX6426 GND Figure 1. MAX6340/MAX6423/MAX6425/MAX6426 Open-Drain RESET Output Allows Use with Multiple Supplies Selecting a Reset Capacitor The reset timeout period is adjustable to accommodate a variety of µP applications. Adjust the reset timeout period (tRP) by connecting a capacitor (CSRT) between SRT and ground. Calculate the reset timeout capacitor as follows: _______________________________________________________________________________________ Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay Operating as a Voltage Detector The MAX6340/MAX6421–MAX6426 can be operated in a voltage detector mode by floating the SRT pin. The reset delay times for VCC rising above or falling below the threshold are not significantly different. The reset output is deasserted smoothly without false pulses. VCC VDD 10kΩ MAX6340 MAX6423 MAX6425 MAX6426 µP RESET N GND OPEN-DRAIN LOGIC N Figure 2. Wired-OR Reset Circuit RESET Applications Information Interfacing to Other Voltages for Logic Compatibility The open-drain outputs of the MAX6340/MAX6423/ MAX6425/MAX6426 can be used to interface to µPs with other logic levels. As shown in Figure 1, the open-drain output can be connected to voltages from 0 to 5.5V. This allows for easy logic compatibility to various µPs. Wired-OR Reset To allow auxiliary circuitry to hold the system in reset, an external open-drain logic signal can be connected to the open-drain RESET of the MAX6340/MAX6423/ MAX6425/MAX6426, as shown in Figure 2. This configuration can reset the µP, but does not provide the reset timeout when the external logic signal is released. Negative-Going VCC Transients In addition to issuing a reset to the µP during power-up, power-down, and brownout conditions, these supervisors are relatively immune to short-duration negative-going transients (glitches). The graph Maximum Transient Duration vs. Reset Threshold Overdrive in the Typical Operating Characteristics shows this relationship. The area below the curve of the graph is the region in which these devices typically do not generate a reset pulse. This graph was generated using a negativegoing pulse applied to VCC, starting above the actual reset threshold (VTH) and ending below it by the magnitude indicated (reset-threshold overdrive). As the magnitude of the transient decreases (farther below the reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 100mV below the reset threshold and lasts 50µs or less does not cause a reset pulse to be issued. Ensuring a Valid RESET or RESET Down to VCC = 0 When VCC falls below 1V, RESET/RESET current-sinking (sourcing) capabilities decline drastically. In the case of the MAX6421/MAX6424, high-impedance CMOS-logic inputs connected to RESET can drift to undetermined voltages. This presents no problems in most applications, since most µPs and other circuitry do not operate with VCC below 1V. In those applications where RESET must be valid down to zero, adding a pulldown resistor between RESET and ground sinks any stray leakage currents, holding RESET low (Figure 3). The value of the pulldown resistor is not critical; 100kΩ is large enough not to load RESET and small enough to pull RESET to ground. For applications using the MAX6422, a 100kΩ pullup resis- _______________________________________________________________________________________ 5 MAX6340/MAX6421–MAX6426 CSRT = (tRP - 275µs) / (2.73 ✕ 106) where tRP is in seconds and CSRT is in farads. The reset delay time is set by a current/capacitor-controlled ramp compared to an internal 0.65V reference. An internal 240nA ramp current source charges the external capacitor. The charge to the capacitor is cleared when a reset condition is detected. Once the reset condition is removed, the voltage on the capacitor ramps according to the formula: dV/dt = I/C. The CSRT capacitor must ramp to 0.65V to deassert the reset. CSRT must be a low-leakage (<10nA) type capacitor; ceramic is recommended. MAX6340/MAX6421–MAX6426 Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay Table 1. Reset Threshold Voltage Suffix VCC SUFFIX MIN TYP MAX 16 1.536 1.575 1.614 17 1.623 1.665 1.707 18 1.755 1.800 1.845 19 1.853 1.900 1.948 20 1.950 2.000 2.050 21 2.048 2.100 2.153 22 2.133 2.188 2.243 23 2.313 2.313 2.371 24 2.340 2.400 2.460 25 2.438 2.500 2.563 26 2.559 2.625 2.691 27 2.633 2.700 2.768 28 2.730 2.800 2.870 29 2.852 2.925 2.998 30 2.925 3.000 3.075 31 2.998 3.075 3.152 32 3.120 3.200 3.280 33 3.218 3.300 3.383 34 3.315 3.400 3.485 35 3.413 3.500 3.558 36 3.510 3.600 3.690 37 3.608 3.700 3.793 38 3.705 3.800 3.895 39 3.803 3.900 3.998 40 3.900 4.000 4.100 41 3.998 4.100 4.203 42 4.095 4.200 4.305 43 4.193 4.300 4.408 44 4.266 4.375 4.484 45 4.388 4.500 4.613 Layout Consideration 46 4.509 4.625 4.741 SRT is a precise current source. When developing the layout for the application, be careful to minimize board capacitance and leakage currents around this pin. Traces connected to SRT should be kept as short as possible. Traces carrying high-speed digital signals and traces with large voltage potentials should be routed as far from SRT as possible. Leakage current and stray capacitance (e.g., a scope probe) at this pin could cause errors in the reset timeout period. When evaluating these parts, use clean prototype boards to ensure accurate reset periods. 47 4.583 4.700 4.818 48 4.680 4.800 4.920 49 4.778 4.900 5.023 50 4.875 5.000 5.125 VCC MAX6421 MAX6424 RESET 100kΩ GND Figure 3. Ensuring RESET Valid to VCC = 0 VCC 100kΩ VCC MAX6422 RESET GND Figure 4. Ensuring RESET Valid to VCC = 0 tor between RESET and VCC holds RESET high when VCC falls below 1V (Figure 4). Open-drain RESET versions are not recommended for applications requiring valid logic for VCC down to zero. 6 _______________________________________________________________________________________ Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay TOP MARK PART* OUTPUT STAGE TOP MARK Open-Drain RESET AEBE MAX6423US16-T Open-Drain RESET KADC Open-Drain RESET AEBG MAX6423XS16-T Open-Drain RESET ADUF MAX6340UK26-T Open-Drain RESET AEBI MAX6423US22-T Open-Drain RESET KADU MAX6340UK29-T Open-Drain RESET AEBJ MAX6423XS22-T Open-Drain RESET ADUK MAX6340UK46-T Open-Drain RESET AEBM MAX6423US26-T Open-Drain RESET KADW MAX6421US16-T Push-Pull RESET KADA MAX6423XS26-T Open-Drain RESET ADUM PART* OUTPUT STAGE MAX6340UK16-T MAX6340UK22-T MAX6421XS16-T Push-Pull RESET ACU MAX6423US29-T Open-Drain RESET KADX MAX6421US22-T Push-Pull RESET KADE MAX6423XS29-T Open-Drain RESET ADUN MAX6421XS22-T Push-Pull RESET ACY MAX6423US46-T Open-Drain RESET KAEA MAX6421US26-T Push-Pull RESET KADG MAX6423XS46-T Open-Drain RESET ADUQ MAX6421XS26-T Push-Pull RESET ADA MAX6424UK16-T Push-Pull RESET ADUF MAX6421US29-T Push-Pull RESET KADH MAX6424UK22-T Push-Pull RESET ADUK ADUM MAX6421XS29-T Push-Pull RESET ADB MAX6424UK26-T Push-Pull RESET MAX6421US46-T Push-Pull RESET KADK MAX6424UK29-T Push-Pull RESET ADUN MAX6421XS46-T Push-Pull RESET ADE MAX6424UK46-T Push-Pull RESET ADUQ MAX6422US16-T Push-Pull RESET KABD MAX6425UK16-T Open-Drain RESET ADUG MAX6422XS16-T Push-Pull RESET ACV MAX6425UK22-T Open-Drain RESET ADUS MAX6422US22-T Push-Pull RESET KADM MAX6425UK26-T Open-Drain RESET ADUU MAX6422XS22-T Push-Pull RESET ADG MAX6425UK29-T Open-Drain RESET ADUV MAX6422US26-T Push-Pull RESET KADO MAX6425UK46-T Open-Drain RESET ADUY MAX6422XS26-T Push-Pull RESET ADI MAX6426UK16-T Open-Drain RESET ADUH MAX6422US29-T Push-Pull RESET KADP MAX6426UK22-T Open-Drain RESET ADVA MAX6422XS29-T Push-Pull RESET ADJ MAX6426UK26-T Open-Drain RESET ADVC MAX6422US46-T Push-Pull RESET KADS MAX6426UK29-T Open-Drain RESET ADVD MAX6422XS46-T Push-Pull RESET ADM MAX6426UK46-T Open-Drain RESET ADVG Typical Operating Circuit *Sample stock is generally held on all standard versions. Contact factory for availability of nonstandard versions. VCC VCC LASER-TRIMMED RESISTORS µP VREF RESET SRT RESET TIMEOUT CSRT RESET MAX6421 MAX6424 GND _______________________________________________________________________________________ 7 MAX6340/MAX6421–MAX6426 Standard Versions Table Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay MAX6340/MAX6421–MAX6426 Pin Configurations (continued) TOP VIEW 5 RESET SRT 1 GND 2 MAX6340 N.C. 3 RESET 1 VCC 2 4 VCC GND 1 4 N.C. 5 VCC 4 RESET SOT23 4 RESET (RESET) 3 SRT MAX6421U MAX6422U MAX6423U VCC 2 SRT MAX6424 MAX6425 GND 3 SOT23 5 SRT 1 GND 2 MAX6426 GND 3 SOT143 SOT23 Selector Guide PART PUSH-PULL RESET PUSH-PULL RESET OPEN-DRAIN RESET MAX6340 — — ✔ 5 SOT23 MAX6421 ✔ — — 4 SOT143/SC70 MAX6422 — ✔ — 4 SOT143/SC70 MAX6423 — — ✔ 4 SOT143/SC70 PIN-PACKAGE MAX6424 ✔ — — 5 SOT23 MAX6425 — — ✔ 5 SOT23 Chip Information TRANSISTOR COUNT: 295 PROCESS: BiCMOS 8 _______________________________________________________________________________________ Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay SC70, 4L.EPS _______________________________________________________________________________________ 9 MAX6340/MAX6421–MAX6426 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) SOT5L.EPS MAX6340/MAX6421–MAX6426 Low-Power, SC70/SOT µP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay 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. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.