19-1568; Rev 2; 12/05 6-Pin µP Reset Circuit with Power-Fail Comparator Features The MAX6342–MAX6345 family of microprocessor (µP) supervisory circuits monitors power supplies in digital systems. These devices significantly improve system reliability and accuracy compared to separate ICs or discrete components. The MAX6342–MAX6345 provide factory-trimmed VCC reset threshold voltages from 2.33V to 4.63V and operate with supply voltages between +1V and +5.5V. A +1.25V threshold detector allows for a power-fail warning, for low-battery detection, or for monitoring another power supply. The MAX6342 contains an MR input and an active-low push-pull reset. The MAX6343 and MAX6344 are identical to the MAX6342 except they provide an active-low, open-drain reset and an active-high, pushpull reset, respectively. The MAX6345 provides a second reset output in place of the MR input to give it an activehigh push-pull reset and an active-low push-pull reset. All of the devices are packaged in a miniature 6-pin SOT23. ♦ Small 6-Pin SOT23 Package ♦ Precision Factory-Set VCC Reset Thresholds Between 2.33V and 4.63V ♦ Guaranteed RESET Valid to VCC = +1V ♦ 100ms min Reset Pulse Width ♦ Debounced CMOS-Compatible Manual-Reset Input ♦ Voltage Monitor for Power-Fail or Low-Battery Warning Ordering Information TEMP RANGE PIN-PACKAGE MAX6342_UT-T PART -40°C to +125°C 6 SOT23-6 MAX6343_UT-T MAX6344_UT-T MAX6345_UT-T -40°C to +125°C -40°C to +125°C -40°C to +125°C 6 SOT23-6 6 SOT23-6 6 SOT23-6 Note: The MAX6342–MAX6345 are available with factory-set reset thresholds from 2.33V to 4.63V (see Selector Guides 1, 2). Insert the letter corresponding to the desired nominal reset threshold into the blank following the part number. There is a 2500 piece order increment required for the SOT package. SOT Top Marks table appears at end of data sheet. Applications Portable Computers Telecom Equipment Networking Equipment Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing “-T” with “+T” when ordering. Portable/Battery-Powered Equipment Multivoltage Systems Pin Configurations Embedded Control Systems Typical Operating Circuit appears at end of data sheet. TOP VIEW Selector Guide 1 SUFFIX RESET THRESHOLD (V) L 4.63 M 4.38 T 3.08 S 2.93 R 2.63 Z 2.33 VCC 1 GND 2 MAX6342 MAX6343 MAX6344 PFI 3 6 RESET (RESET) 5 MR 4 PFO ( ) ARE FOR MAX6344 ONLY. SOT23-6 Pin Configurations continued at end of data sheet. Selector Guide 2 PART PUSH-PULL RESET OUTPUT OPEN-DRAIN RESET OUTPUT PUSH-PULL RESET OUTPUT MANUAL-RESET INPUT MAX6342 ✔ — ✔ MAX6343 — — ✔ — ✔ — — ✔ ✔ MAX6344 — ✔ — MAX6345 ✔ ________________________________________________________________ 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 MAX6342–MAX6345 General Description MAX6342–MAX6345 6-Pin µP Reset Circuit with Power-Fail Comparator ABSOLUTE MAXIMUM RATINGS VCC to GND ..............................................................-0.3V to +6V RESET, RESET (MAX6342/MAX6344/MAX6345) ......... -0.3V to (VCC + 0.3V) RESET (MAX6343)................................................... -0.3V to +6V MR, PFI, PFO ..............................................-0.3V to (VCC + 0.3V) Input Current, VCC ..............................................................50mA Output Current, RESET, RESET ..........................................50mA Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 4mW/°C above +70°C).............320mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature Range (soldering, 10s)..................... +300°C 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 = +1.0V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C and VCC = +3V.) (Note 1) PARAMETER SYMBOL Supply Voltage Range VCC Supply Current Reset Threshold ICC VTH VCC to Reset Delay VOL RESET and RESET Outputs Drive Capability (Note 2) VOH 2 CONDITIONS MIN TYP MAX TA = 0°C to +70°C 1.0 5.5 TA = -40°C to +125°C VCC = 3V, TA = -40° to +85°C VCC = 5.5V, TA = -40° to +85°C No load VCC = 3V, TA = -40° to +125°C VCC = 5.5V, TA = -40° to +125°C TA = +25°C MAX634_L TA = -40°C to +85°C TA = -40°C to +125°C TA = +25°C MAX634_M TA = -40°C to +85°C TA = -40°C to +125°C TA = +25°C TA = -40°C to +85°C MAX634_T TA = -40°C to +125°C TA = +25°C MAX634_S TA = -40°C to +85°C TA = -40°C to +125°C TA = +25°C MAX634_R TA = -40°C to +85°C TA = -40°C to +125°C TA = +25°C MAX634_Z TA = -40°C to +85°C TA = -40°C to +125°C VCC = VTH to (VTH - 100mV) VCC > 1.2V, ISINK = 100µA VCC > 2.7V, ISINK = 1.2mA VCC > 4.5V, ISINK = 3.2mA VCC > 1.2V, ISOURCE = 50µA 1.2 5.5 40 50 50 60 4.70 4.75 4.86 4.45 4.50 4.56 3.13 3.15 3.23 2.97 3.00 3.08 2.67 2.70 2.76 2.36 2.38 2.45 0.8 ✕ VCC VCC > 2.7V, ISOURCE = 500µA (MAX6342/MAX6345 only) 0.8 ✕ VCC VCC > 4.5V, ISOURCE = 800µA (MAX6342/MAX6345 only) 0.8 ✕ VCC 4.56 4.50 4.40 4.31 4.25 4.16 3.03 3.00 2.92 2.89 2.85 2.78 2.59 2.55 2.50 2.30 2.25 2.21 25 30 25 30 4.63 4.38 3.08 2.93 2.63 2.33 20 V µA µA V µs 0.4 0.3 0.4 _______________________________________________________________________________________ UNITS V V 6-Pin µP Reset Circuit with Power-Fail Comparator MAX6342–MAX6345 ELECTRICAL CHARACTERISTICS (continued) (VCC = +1.0V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C and VCC = +3V.) (Note 1) PARAMETER SYMBOL Reset Timeout Period tRP Open-Drain RESET Output Leakage Current (Note 3) ILKG MR Input Low VIL MR Input High VIH CONDITIONS MIN TYP TA = -40°C to +85°C 100 180 TA = -40°C to +125°C 80 MAX UNITS 280 ms 360 1 MAX6343 only, VCC > VTH(MAX) µA V 0.3 ✕ VCC V 0.7 ✕ VCC 60 MR Pull-Up Resistance MR Minimum Pulse Width kΩ 1 µs MR Glitch Rejection 0.1 µs MR to Reset Delay 0.2 µs PFI Input Threshold TA = -40°C to +85°C 1.2 TA = -40°C to +125°C 1.15 1.25 ±0.01 TA = -40°C to +85°C PFI Leakage Current (Note 3) 1.3 V 1.35 ±25 nA ±100 TA = -85°C to +125°C PFO Output Voltage VOL VCC = 4.5V, ISINK = 3.2mA PFO Output Voltage VOH VCC = 4.5V, ISOURCE = 800µA 0.4 V V 0.8 ✕ VCC PFO Output Short-Circuit Current Output sink current 20 Output source current 5 PFI to PFO Delay VOVERDRIVE = 15mV 3 mA µs Note 1: Overtemperature limits are guaranteed by design and not production tested. Note 2: Apply to each part in accordance with threshold voltage, output configuration, and manual reset status selected. Note 3: Leakage parameters are guaranteed by design and not production tested. Typical Operating Characteristics (VPFI = VCC = +5V, TA = +25°C, unless otherwise noted.) VCC VCC VCC = 3.3V MAX6342-03 VCC = 5V 25 SUPPLY CURRENT (µA) MAX6342-02 MAX6342-01 30 MAX6342M/MAX6345M RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE MAX6344L/MAX6345L RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. SUPPLY VOLTAGE AND TEMPERATURE 20 VCC = 2.5V 15 1V/div 10 1V/div RESET 0 VCC = 1V 5 0 RESET 0 0 0 -40 -15 10 35 60 85 1sec/div 1sec/div TEMPERATURE (°C) _______________________________________________________________________________________ 3 Typical Operating Characteristics (continued) (VPFI = VCC = +5V, TA = +25°C, unless otherwise noted.) PFO OUTPUT-VOLTAGE LOW vs. SUPPLY VOLTAGE PFO OUTPUT-VOLTAGE HIGH vs. SUPPLY VOLTAGE RL = 10kΩ 5 MAX6342-05 0.60 MAX6342-04 6 RL = 1kΩ 0.55 0.50 4 0.45 PFO (V) PFO (V) 3 0.40 0.35 2 0.30 1 0.25 0.20 0 1 2 3 4 5 0 6 1 2 3 4 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) MAX6344/MAX6345 RESET RESPONSE TIME MAX6342/MAX6345 RESET RESPONSE TIME 5V VCC 4V 5V 4V 5V 5 6 MAX6342-07 0 MAX6342-06 MAX6342–MAX6345 6-Pin µP Reset Circuit with Power-Fail Comparator VCC RESET 4V 4V RESET 0 0 2µs/div 10µs/div Pin Description PIN NAME 4 FUNCTION MAX6342 MAX6343 MAX6344 MAX6345 1 1 1 1 VCC Supply Voltage 2 2 2 2 GND Ground 3 3 3 3 PFI Power-Fail Voltage Monitor Input. When PFI is < 1.25V, PFO goes low. Connect PFI to GND or VCC when not used. 4 4 4 4 PFO Power-Fail Voltage Monitor Output _______________________________________________________________________________________ 6-Pin µP Reset Circuit with Power-Fail Comparator PIN MAX6342 MAX6343 MAX6344 NAME FUNCTION Manual-Reset Input. Pull low to force a reset. RESET or RESET remains active as long as MR is low and for the reset timeout period after MR goes high. Leave unconnected or connect to VCC if unused. MAX6345 5 5 5 — MR 6 6 — 5 RESET Active-Low Reset Output. Push-pull for MAX6342/MAX6345. Open-drain for MAX6343. It remains low for 180ms after VCC rises above the reset threshold or MR goes from low to high. — — 6 6 RESET Active-High Push-Pull Reset Output. It remains high for 180ms after VCC rises above the reset threshold or MR goes from low to high. 1 VCC 1 VCC RESET GENERATOR VTH GND RESET GENERATOR RESET VCC (RESET) RESET 6 VTH 100kΩ MAX6342 MAX6343 MAX6344 2 6 5 2 MR MAX6345 GND 3 RESET 5 3 4 PFI PFO 4 PFI PFO 1.25V 1.25V ( ) ARE FOR MAX6344 ONLY. Figure 1. MAX6342/MAX6343/MAX6344 Functional Diagram _______________Detailed Description Reset Output A µP’s reset input starts the µP in a known state. These µP supervisory circuits assert reset to prevent codeexecution errors during power-up, power-down, or brownout conditions. RESET and RESET are guaranteed to be asserted at a valid logic level for VCC > +1V (see the Electrical Characteristics table). Once RESET asserts, it remains asserted for at least 100ms (tRP) after VCC rises above its threshold value or after MR returns high (Figures 1 and 2). Figure 2. MAX6345 Functional Diagram Open-Drain RESET Output The MAX6343 has an active-low, open-drain reset output. This output sinks current when RESET is asserted. Connect a pull-up resistor from RESET to any positive supply voltage up to +5.5V (Figure 3). Select a resistor value large enough to register a logic low (see the Electrical Characteristics table), and small enough to register a logic high while supplying all input current and leakage paths connected to the RESET line. A 10kΩ pull-up is sufficient in most applications. Manual Reset The MAX6342/MAX6343/MAX6344s’ manual-reset input (MR) allows reset to be triggered by a pushbutton switch. The switch is effectively debounced by the 1µs min reset pulse width. MR is CMOS-logic compatible. _______________________________________________________________________________________ 5 MAX6342–MAX6345 Pin Description (continued) 160 +5.0V +3.3V VCC 10kΩ VCC µP RESET RESET MAX6343 MAXIMUM TRANSIENT DURATION (µs) MAX6342–MAX6345 6-Pin µP Reset Circuit with Power-Fail Comparator 140 120 100 80 MAX634_L/M 60 40 MAX634_T/S/R/Z 20 0 GND 1 10 100 1000 RESET COMPARATOR OVERDRIVE, VTH - VCC (mV) Figure 3. Open-Drain RESET Output Allows Use with Multiple Supplies VCC VCC VCC GND MAX6342 MAX6345 100kΩ RESET VCC RESET GND MAX6344 100kΩ Figure 5. Ensuring RESET Valid to VCC = 0 on Active-Low Push-Pull Outputs Power-Fail Comparator The power-fail comparator is useful for various purposes because the power-fail output (PFO) is independent of the reset output. The inverting input is internally connected to a +1.25V reference. To build an early-warning circuit for power failure, connect the PFI pin to a voltage divider (see the Typical Oper-ating Circuit). Choose the voltage-divider ratio so that the voltage at PFI falls below +1.25V just before the +5V regulator drops out. Use PFO to interrupt the µP to prepare for an orderly shutdown. Applications Information Negative-Going VCC Transients The MAX6342–MAX6345 supervisors are immune to short-duration, negative-going VCC transients (glitches) that usually do not require the entire system to shut down. Figure 4 shows typical transient duration vs. reset comparator overdrive, for which the MAX6342–MAX6345 do not generate a reset pulse. The graph was generated using a negative-going pulse applied to VCC, starting 6 Figure 4. Maximum Transient Duration Magnitude Rejection MAX6345 Figure 6. Ensuring RESET Valid to VCC = 0 on Active-High Push-Pull Outputs 0.5V above the actual reset threshold and ending below it by the magnitude indicated (reset comparator overdrive). The graph indicates the maximum pulse width a negative-going VCC transient can have without causing a reset pulse. As the magnitude of the transient increases (goes further below the reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 100mV below the reset threshold and lasts 12µs or less will not cause a reset pulse. A 1µF bypass capacitor mounted as close as possible to the VCC pin provides additional transient immunity. Ensuring a Valid Reset Output Down to VCC = 0 The MAX6342–MAX6345 are guaranteed to operate properly down to VCC = +1V. In applications that require valid reset levels down to VCC = 0, a pulldown resistor to active-low outputs (MAX6342/MAX6345) and a pullup resistor to active-high outputs (MAX6344/MAX6345) ensure that the reset line is valid when the reset output is no longer sinking or sourcing current (Figures 5 and 6). _______________________________________________________________________________________ 6-Pin µP Reset Circuit with Power-Fail Comparator BUFFERED RESET TO OTHER SYSTEM COMPONENTS RESET (RESET) VCC R1 PFI R2 TO µP VCC MAX6342 MR MAX6343 MAX6344 VCC µP MAX6342 MAX6345 PFO GND 4.7kΩ RESET ( ) ARE FOR MAX6344 ONLY. RESET GND GND Figure 7. Monitoring Two Supplies VCC Figure 9. Interfacing to µPs with Bidirectional Reset I/O Monitoring a Negative Voltage R1 VCC 100kΩ MR MAX6342 MAX6343 PFO PFI MAX6344 100kΩ R2 GND V- RESET (RESET) VCC - 1.25V = 1.25V - VTRIP R1 R2 VTRIP < 0 ( ) ARE FOR MAX6344 ONLY. Connect the circuit as shown in Figure 8 to use the power-fail comparator to monitor a negative supply rail. PFO stays low when V- is good. When V- rises to cause PFI to be above +1.25V, PFO goes high. By adding the resistors and transistor as shown, a high PFO triggers reset. As long as PFO remains high, the MAX6342/ MAX6343/MAX6344 will keep reset asserted. Note that the accuracy of this circuit depends on the PFI threshold tolerance, the VCC line voltage, and the resistors. Also, ensure that the voltage at PFI remains above GND. Interfacing to µPs with Bidirectional Reset Pins Figure 8. Monitoring a Negative Voltage Note that this method does not work with the open-drain output of the MAX6343. The resistor value used is not critical, but it must be large enough not to load the reset output when VCC is above the reset threshold. For most applications, 100kΩ is adequate. Monitoring Two Supplies Monitor another voltage by connecting a resistor-divider to PFI as shown in Figure 7. The threshold voltage will then be given by: VTH(PFI) = 1.25[(R1 + R2) / R2] where VTH(PFI) is the threshold at which the monitored voltage will trip PFO. A good rule of thumb for selecting the resistors is to choose R2 between 250kΩ and 500kΩ and solve for R1. Connect PFO to MR in applications that require reset to assert when the second voltage falls below its threshold. SOT Top Marks SOT TOP MARK PART SOT TOP MARK MAX6342LUT-T AACP MAX6344LUT-T AADQ MAX6342MUT-T AACQ MAX6344MUT-T AADR MAX6342TUT-T AACR MAX6344TUT-T AADS MAX6342SUT-T AACS MAX6344SUT-T AADT MAX6342RUT-T AACT MAX6344RUT-T AADU MAX6342ZUT-T AACU MAX6344ZUT-T AADV MAX6343LUT-T AACV MAX6345LUT-T AADW MAX6343MUT-T AACW MAX6345MUT-T AADX MAX6343TUT-T AACX MAX6345TUT-T AADY MAX6343SUT-T AACY MAX6345SUT-T AADZ MAX6343RUT-T AACZ MAX6345RUT-T AAEA MAX6343ZUT-T AADA MAX6345ZUT-T AAEB PART _______________________________________________________________________________________ 7 MAX6342–MAX6345 VCC V+ Typical Operating Circuit UNREGULATED DC Pin Configurations (continued) TOP VIEW LINEAR REGULATOR VCC 1 VCC PFI RESET MAX6342 MR PFO VCC GND 2 RESET µP PFI 3 INTERRUPT MAX6345 6 RESET 5 RESET 4 PFO SOT23-6 Chip Information PUSHBUTTON SWITCH TRANSISTOR COUNT: 403 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.) 6LSOT.EPS MAX6342–MAX6345 6-Pin µP Reset Circuit with Power-Fail Comparator PACKAGE OUTLINE, SOT 6L BODY 21-0058 G 1 1 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.