Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset

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1 9-2523; Rev ; /5 Microprocessor Supervisory Reset Circuits General Description The microprocessor (µp) supervisory circuits monitor single power-supply voltages from +.8 to +5. and assert a reset if the supply voltage drops below its preset threshold. An edge-triggered, one-shot manual reset function ensures that the µp enters the reset mode for a fixed timeout period only, even in the event of a continuously asserted manual reset. The significantly improve system reliability compared to traditional manual reset supervisory circuits. A variety of factory-trimmed threshold options accommodate different supply voltages and tolerances, eliminating external components. The factory-set thresholds range from to to monitor +5., +3.3, +3., +2.5, and +.8 supplies with various tolerances. Reset timeout periods of 5ms (min) and 2ms (min) are available to accommodate different µp platforms. A single, active-low output asserts when drops below its threshold or if the edge-triggered asserts low. remains low for the reset timeout period after rises above its threshold and for a fixed, one-shot timeout period after a manual reset input falling edge. remains valid as long as remains above +. Open-drain (MAX6467) and push-pull (MAX6468) output options provide additional flexibility in the system design. The are offered in the space-saving 4-pin SOT43 package and the ultra-small 4-pin SC7 package and are specified over the automotive (-4 C to +25 C) temperature range. Cell Phones/PDAs Embedded Control Systems Industrial Equipment Automotive Products Portable/Battery-Powered Equipment Medical Devices DSL Modems MP3 Players GPS Systems Digital Cameras Applications Features Precision Factory-Set Reset Threshold oltages for +5., +3.3, +3., +2.5, and +.8 Supplies Edge-Triggered Manual Reset Input with One- Shot Pulsed Reset Output Two Reset Timeout Period Options (5ms or 2ms min) Immune to Short oltage Transients Low Supply Current (3µA at = +.8) alid to = + Active-Low Open-Drain and Push-Pull Output Options -4 C to +25 C Operating Temperature Range Small 4-Pin SC7 and SOT43 Packages No External Components Required Pin Compatible with MAX8, MAX635, MAX6384, and MAX6386 Ordering Information PART TEMP RANGE PIN-PACKAGE MAX6467XS D_-T -4 C to +25 C 4 SC7-4 MAX6467US D_-T -4 C to +25 C 4 SOT43-4 MAX6468XS D_-T -4 C to +25 C 4 SC7-4 MAX6468US D_-T -4 C to +25 C 4 SOT43-4 Note: Insert reset threshold suffix (see Reset Threshold table) after XS or US. Insert reset timeout delay (see Reset Timeout Delay table) after D to complete the part number. Sample stock is generally held on standard versions only (see Standard ersions table). Standard versions have an order increment requirement of 25 pieces. Nonstandard versions have an order increment requirement of, pieces. Contact factory for availability. Devices are available in both leaded and lead-free packaging. Specify lead-free by replacing T with +T when ordering. TOP IEW 2 Pin Configurations MAX6467XS MAX6468XS 4 3 Typical Operating Circuit appears at end of data sheet. SC7 Pin Configurations continued at end of data sheet. Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS to to +6. to Open-Drain to +6. Push-Pull to ( +.3) to to ( +.3) Input/Output Current (all pins)...2ma 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 Continuous Power Dissipation (T A = +7 C) 4-Pin SC7 (derate 3.mW/ C above +7 C)...245mW 4-Pin SOT43 (derate 4mW/ C above +7 C)...32mW Operating Temperature Range...-4 C to +25 C Storage Temperature Range C to +5 C Junction Temperature...+5 C Lead Temperature (soldering, s)...+3 C ( = +.2 to +5.5, T A = -4 C to +25 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note ) PARAMETER SYM B O L CONDITIONS MIN TYP MAX UNITS T A = C to +25 C. 5.5 Operating oltage Range T A = -4 C to C Supply Current Reset Threshold (See the Reset Threshold Table) I CC = +5.5, no load 7 3 = +3.6, no load 6 = +2.5, no load 4 8 = +.8, no load T A = +25 C -.5% TH +.5% TH T A = -4 C to +85 C -2.5% +2.5% T A = +85 C to +25 C -3% +3% µa Reset Delay t RD falling at m/µs from TH + m to TH - m 35 µs D3 option Reset Timeout Period t RP D7 option Timeout Period t P D3 and D7 options ms Rising Debounce Period (Note 2) Input oltage t DEB D3 and D7 options ms IL TH < +4 IH.7 x.3 x IL.8 TH +4 IH 2.4 Minimum Input Pulse µs Glitch Rejection ns to Delay 2 ns Pullup Resistance to Ω Output High (MAX6468 Only) OH +2.5, I SOURCE = 5µA, not asserted +4.5, I SOURCE = 8µA, not asserted.8 x ms.8 x 2

3 ELECTRICAL CHARACTERISTICS (continued) ( = +.2 to +5.5, T A = -4 C to +25 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note ) PARAMETER SYM B O L CONDITIONS MIN TYP MAX UNITS +, I SINK = 8µA, asserted , I SINK =.2mA, Output Low OL asserted +4.5, I SINK = 3.2mA, Output Leakage Current (MAX6467 Only) asserted I LKG not asserted µa Note : Specifications over temperature are guaranteed by design. Production testing at T A = +25 C only. Note 2: The input ignores falling edges that occur within the rising debounce period (t DEB ) after first rises from low to high (after a valid reset assertion). This prevents invalid reset assertion due to switch bounce. Typical Operating Characteristics ( = +5, MAX6468US29D3 device, T A = +25 C, unless otherwise noted.).3.3 SUPPLY CURRENT (µa) SUPPLY CURRENT vs. TEMPERATURE = +5.5 = +3.6 = +2.5 = +.8 MAX6467 toc SUPPLY CURRENT (µa) SUPPLY CURRENT vs. SUPPLY OLTAGE MAX6467 toc2 CC TO DELAY (µs) TO DELAY vs. TEMPERATURE = TH + m TO TH - m MAX6467 toc SUPPLY OLTAGE () TIMEOUT PERIOD (ms) TIMEOUT PERIOD vs. TEMPERATURE MAX6467 toc4 NORMALIZED THRESHOLD () NORMALIZED THRESHOLD vs. TEMPERATURE MAX6467 toc5 OL (m) = 5. OUTPUT OLTAGE LOW vs. SINK CURRENT I SINK (ma) MAX6467 toc6 3

4 Typical Operating Characteristics (continued) ( = +5, MAX6468US29D3 device, T A = +25 C, unless otherwise noted.) OH () OUTPUT OLTAGE HIGH vs. SOURCE CURRENT = I SOURCE (ma) MAX6467 toc7 MAXIMUM TRANSIENT DURATION (µs) MAXIMUM TRANSIENT DURATION vs. THRESHOLD OERDRIE ASSERTS ABOE THIS LINE THRESHOLD OERDRIE (m) MAX6467 toc8 TO DELAY (ns) TO DELAY vs. TEMPERATURE MAX6467 toc9 PROPAGATION DELAY (WITH m OERDRIE) MAX6467 toc 4µs/div 3. m/div AC-COUPLED /div PULLUP AND PULLDOWN RESPONSE C = 47pF, R PULLUP = kω, PULLUP =.6 MAX6467 toc.675 2m/div.475 TIMEOUT PERIOD MAX6467 toc /div.6 5m/div 3.3 2/div MAX6467_S6D3-T 4µs/div 4ms/div 4

5 PIN NAME FUNCTION Ground 2 3 Pin Description Reset Output. is an active-low open-drain (MAX6467) or push-pull (MAX6468) output. asserts low when drops below the selected threshold and remains low for the reset timeout period after rises above the threshold. The one-shot asserts low for a fixed reset timeout period on the falling edge of the manual reset input. The open-drain output requires an external pullup resistor. Manual Reset Input. Drive low to initiate a reset output. controls an edge-triggered one-shot that asserts low for a fixed timeout period when is driven low. Internal timing circuitry ignores switch close and open bounce to ensure proper one-shot reset timing. 4 below the selected threshold, asserts low and remains low for the reset timeout period after rises Power-Supply Input. provides power to the device and is also a monitored voltage. When drops above the threshold. For better noise immunity, bypass to with a.µf capacitor. TH SWITCH BOUNCE SWITCH BOUNCE SWITCH BOUNCE t RP t P t DEB t P Figure. Timing Diagram Detailed Description Reset Output The MAX6467 provides an active-low open-drain output. The MAX6468 provides an active-low push-pull output. asserts low if drops below the selected threshold or if a falling edge occurs on. remains low for the reset timeout period after increases above the threshold voltage or is one-shot pulsed low for the timeout period after a falling edge on. Manual Reset Input Many µp-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A falling edge on asserts low. is one-shot pulsed low for the timeout period after a falling edge on. An internal.5kω pullup resistor to CC allows to be left unconnected if not used. can be driven with TTL or CMOSlogic levels, or with open-drain/collector outputs. Connect a normally open momentary pushbutton switch from to to realize a manual reset function. External debounce circuitry is not required, as the MAX6467/ MAX6468 respond to the first falling edge on and ignore subsequent falling edges within the reset timeout period and during the debounce period (see Figure ). After goes high for 5ms (t DEB ), the manual reset one-shot is ready to trigger a reset on the next falling edge. Connect a.µf capacitor from to when using long cables to provide additional noise immunity (Figure 2). 5

6 TIMEOUT SUFFIX TIMEOUT PERIOD (min/max) (ms) Applications Information Falling CC Transients In addition to issuing a reset to the µp during power-up, power-down, and brownout conditions, the MAX6467/ MAX6468 are relatively immune to short-duration falling transients (glitches). The Typical Operating Characteristics section shows the Maximum Transient Duration vs. Overdrive for which the MAX6467/ MAX6468 do not generate a reset pulse. This graph was generated using a falling pulse applied to starting above the actual reset threshold and ending below the threshold by the magnitude indicated ( Overdrive). The graph indicates the typical maximum pulse width a falling transient can have without initiating a reset pulse. As the magnitude of the transient increases (goes TIMEOUT PERIOD (min/max) (ms) RISING DEBOUNCE PERIOD (min/max) (ms) D3 5/3 5/3 5/3 D7 2/24 5/3 5/3 *Additional reset timeout options may be available. Contact factory for availability. Reset Timeout Delay* farther below the reset threshold), the maximum allowable pulse width decreases. A.µF bypass capacitor from to provides additional transient immunity. Ensuring a alid Output Down to CC = The guarantee proper operation down to = +. In applications that require valid reset levels down to =, a pulldown resistor to active-low outputs (MAX6468 only, Figure 3) ensures that remains valid while the output can no longer sink current. This scheme does not work with the open-drain outputs of the MAX6467. Ensure that the resistor value used does not overload the output when is above the reset threshold. For most applications, use kω to MΩ..5kΩ MAX6467 MAX6468 ONE-SHOT/ DEBOUNCE MAX6468 R kω TIMEOUT PERIOD OUTPUT.23 Figure 3. alid to = Figure 2. Functional Diagram TRANSISTOR COUNT: 748 PROCESS: BiCMOS Chip Information 6

7 PART MAX6467XS6D3 MAX6467XS22D3 MAX6467XS26D3 MAX6467XS29D3 MAX6467XS46D3 MAX6467US6D3 MAX6467US22D3 MAX6467US26D3 MAX6467US29D3 MAX6467US46D3 MAX6468XS6D3 MAX6468XS22D3 MAX6468XS26D3 MAX6468XS29D3 MAX6468XS46D3 MAX6468US6D3 MAX6468US22D3 MAX6468US26D3 MAX6468US29D3 MAX6468US46D3 +. TO +5.5 MAX6467 MAX6468 Standard ersions TOP MARK INPUT AGL AGM AGN AGO AGP KAFN KAFO KAFP KAFQ KAFR AGQ AGR AGS AGC AGB KAFS KAFT KAFU KAEW KAF Typical Operating Circuit µp Reset Threshold (-4 C to +85 C) SUFFIX TH (min) TH (typ) TH (max) Pin Configurations (continued) TOP IEW 2 MAX6467US MAX6468US 4 3 SOT43 7

8 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 SOT-43 4L.EPS PACKAGE OUTLINE, SOT-43, 4L 2-52 E 8

9 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 SC7, 4L.EPS PACKAGE OUTLINE, 4L SC C 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, 2 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.