3-Pin Microprocessor Reset Circuits

Transcription

1 ; Rev 4; 12/99 3-Pin Microprocessor Reset Circuits General Description The MAX803/MAX809/MAX810 are microprocessor (µp) supervisory circuits used to monitor the power supplies in µp and digital systems. They provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with +5, +3.3, +3.0, or +2.5-powered circuits. These circuits perform a single function: they assert a reset signal whenever the supply voltage declines below a preset threshold, keeping it asserted for at least 140ms after has risen above the reset threshold. Reset thresholds suitable for operation with a variety of supply voltages are available. The MAX803 has an open-drain output stage, while the MAX809/MAX810 have push-pull outputs. The MAX803 s open-drain output requires a pull-up resistor that can be connected to a voltage higher than. The MAX803/MAX809 have an active-low output, while the MAX810 has an active-high output. The reset comparator is designed to ignore fast transients on, and the outputs are guaranteed to be in the correct logic state for down to 1. Low supply current makes the MAX803/MAX809/ MAX810 ideal for use in portable equipment. The MAX803 is available in a 3-pin SC70 package, and the MAX809/MAX810 are available in 3-pin SC70 or SOT23 packages. Applications Computers Controllers Intelligent Instruments Critical µp and µc Power Monitoring Portable/Battery-Powered Equipment Automotive *MAX803 ONLY MAX803 MAX809 Typical Operating Circuit R PULL-UP * INPUT µp Features Precision Monitoring of +2.5, +3, +3.3, and +5 Power-Supply oltages Fully Specified Over Temperature Available in Three Output Configurations Open-Drain Output (MAX803) Output (MAX809) Output (MAX810) 140ms min Power-On Reset Pulse Width 12µA Supply Current Guaranteed Reset alid to = +1 Power Supply Transient Immunity No External Components 3-Pin SC70 and SOT23 Packages PART MAX803_EXR-T MAX803_EXR-T10 MAX809_EXR-T MAX809_EXR-T10 MAX809_EUR-T MAX809_EUR-T10 MAX810_EXR-T MAX810_EXR-T10 MAX810_EUR-T MAX810_EUR-T10 Note: These parts are offered in 2.5k or 10k reels, and must be ordered in 2.5k or 10k increments. Order MAX803_EXR-T for 2.5k reels and MAX803_EXR-T10 for 10k reels. Insert the desired suffix letter from the Selector Guide into the blank to complete the part number. All versions of these products may not be available at the time of announcement. Contact factory for availability. TOP IEW () Maxim Integrated Products 1 TEMP. RANGE 1 MAX803 MAX809 MAX810 SC70-3/SOT23-3 ( ) ARE FOR MAX810. MAX803 AAILABLE IN SC70-3 ONLY. Ordering Information 2 Pin Configuration For free samples & the latest literature: or phone For small orders, phone PIN-PACKAGE 3 SOT SOT SOT SOT23-3

2 ABSOLUTE MAXIMUM RATINGS Terminal oltage (with respect to ) to +6.0, (push-pull) to ( + 0.3) (open drain) to +6.0 Input Current,...20mA Output Current,,...20mA Continuous Power Dissipation (T A = +70 C) 3-Pin SC70 (derate 2.17mW/ C above +70 C)...174mW 3-Pin SOT23 (derate 4mW/ C above +70 C)...320mW Operating Temperature Range... Storage Temperature Range C to +150 C Lead Temperature (soldering, 10s) C Rate of Rise,...100/µs 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 ( = full range, T A =, unless otherwise noted. Typical values are at, = 5 for L/M/J versions, = 3.3 for T/S versions, = 3 for R version, and = 2.5 for Z version.) (Note 1) Range PARAMETER Supply Current (SOT23) Supply Current (SC70) Reset Threshold SYMBOL I CC I CC TH CONDITIONS MIN TYP MAX T A = 0 C to +70 C T A = T A = -40 C to +85 C < 5.5, MAX8 J/L/M < 3.6, MAX8 R/S/T T A = +85 C to +105 C < 5.5, MAX8 L/M < 3.6, MAX8 R/S/T T A = -40 C to +85 C < 5.5, MAX8 L/M < 3.6, MAX8 R/S/T/Z T A = +85 C to +105 C < 5.5, MAX8 L/M < 3.6, MAX8 R/S/T/Z MAX8 L T A = -40 C to +85 C T A = +85 C to +105 C MAX8 M T A = -40 C to +85 C T A = +85 C to +105 C MAX809J (SOT only) T A = -40 C to +85 C T A = +85 C to +105 C MAX8 T T A = -40 C to +85 C T A = +85 C to +105 C MAX8 S T A = -40 C to +85 C T A = +85 C to +105 C MAX8 R T A = -40 C to +85 C T A = +85 C to +105 C MAX8 Z (SC70 only) T A = -40 C to +85 C T A = +85 C to +105 C UNITS µa

3 ELECTRICAL CHARACTERISTICS (continued) ( = full range, T A =, unless otherwise noted. Typical values are at, = 5 for L/M/J versions, = 3.3 for T/S versions, = 3 for R version, and = 2.5 for Z version.) (Note 1) PARAMETER Reset Threshold Tempco to Reset Delay (Note 2) Reset Active Timeout Period (SOT23) Reset Active Timeout Period (SC70) Output oltage Low (push-pull active low and opendrain active-low, MAX803 and MAX809) Output oltage High (push-pull active low, MAX809) Output oltage Low (push-pull active high, MAX810) Output oltage High (push-pull active high, MAX810) Open-Drain Output Leakage Current (MAX803) SYMBOL OL OH OL OH = TH to ( TH - 100m) T A = -40 C to +85 C T A = +85 C to +105 C CONDITIONS T A = -40 C to +85 C T A = +85 C to +105 C = TH min, I SINK = 1.2mA, MAX803R/S/T/Z, MAX809R/S/T/Z = TH min, I SINK = 3.2mA, MAX803L/M, MAX809J/L/M > 1.0, I SINK = 50µA > TH max, I SOURCE = 500µA, MAX809R/S/T/Z > TH max, I SOURCE = 800µA, MAX809J/L/M = TH max, I SINK = 1.2mA, MAX810R/S/T/Z = TH max, I SINK = 3.2mA, MAX810L/M 1.8 < < TH min, I SOURCE = 150µA > TH, deasserted Note 1: Production testing done at ; limits over temperature guaranteed by design only. Note 2: output for MAX803/MAX809; output for MAX810. MIN TYP MAX UNITS ppm/ C µs Typical Operating Characteristics ( = full range, T A =, unless otherwise noted. Typical values are at, = +5 for L/M/J versions, = +3.3 for T/S versions, = +3 for R version, and = +2.5 for Z version.) SUPPLY CURRENT (µa) SUPPLY CURRENT vs. TEMPERATURE (SC70 PACKAGE, NO LOAD) MAX8 L/M, = 5 MAX8 R/S/T, = 3.3 MAX8 Z, = 2.5 MAX8 L/M/R/S/T/Z, = 1 MAX803 toc01 POWER-DOWN DELAY (µs) POWER-DOWN DELAY vs. TEMPERATURE (MAX8 R/S/T/Z) 0 OD = 200m OD = TH - OD = 10m OD = 20m OD = 100m MAX803-TOC ms ms µa

4 Typical Operating Characteristics (continued) ( = full range, T A =, unless otherwise noted. Typical values are at, = +5 for L/M/J versions, = +3.3 for T/S versions, = +3 for R version, and = +2.5 for Z version.) POWER-DOWN DELAY (µs) POWER-DOWN DELAY vs. TEMPERATURE (MAX8 J/L/M) PART/SUFFIX MAX803L MAX803M MAX803T MAX803S MAX803R MAX803Z MAX809L MAX809M MAX809J MAX809T MAX809S MAX809R MAX809Z MAX810L MAX810M MAX810T MAX810S OD = TH - OD = 10m OD = 20m OD = 100m OD = 200m POWER-UP TIMEOUT (ms) THRESHOLD () MAX803-TOC4 POWER-UP TIMEOUT vs. TEMPERATURE MAX8 R/S/T/Z MAX8 J/L/M OUTPUT TYPE Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain Open-Drain 4 MAX803-TOC5 NORMALIZED THRESHOLD NORMALIZED THRESHOLD vs. TEMPERATURE AAAA ABAA CWAA ACAA ADAA AFAA AGAA AHAA AJAA AKAA TOP MARK MAX810R 2.63 ALAA AAW MAX810Z 2.32 AAY SOT Selector Guide SC70 AAZ ABA ABB ABC ABD ABE AAN AAO AAP AAQ AAR AAS AAT AAU AA AAX MAX803-TOC6

5 Pin Description PIN NAME FUNCTION 1 Ground 2 (MAX803/ MAX809) (MAX810) Output remains low while is below the reset threshold, and for at least 140ms after rises above the reset threshold. Output remains high while is below the reset threshold, and for at least 140ms after rises above the reset threshold. 3 Supply oltage (+5, +3.3, +3.0, or +2.5) MAXIMUM TRANSIENT DURATION (µs) MAX8 R/S/T/Z MAX8 J/L/M COMPARATOR OERDRIE, TH - (m) Figure 1. Maximum Transient Duration Without Causing a Reset Pulse vs. Reset Comparator Overdrive Detailed Description A microprocessor s (µp s) reset input starts the µp in a known state. The MAX803/MAX809/MAX810 assert reset to prevent code-execution errors during powerup, power-down, or brownout conditions. They assert a reset signal whenever the supply voltage declines below a preset threshold, keeping it asserted for at least 140ms after has risen above the reset threshold. The MAX803 uses an open-drain output, and the MAX809/MAX810 have a push-pull output stage. Connect a pull-up resistor on the MAX803 s output to any supply between 0 and 6. Applications Information Negative-Going CC Transients In addition to issuing a reset to the µp during power-up, power-down, and brownout conditions, the MAX803/ MAX809/MAX810 are relatively immune to short-duration negative-going CC transients (glitches). Figure 1 shows typical transient duration vs. reset comparator overdrive, for which the MAX803/MAX809/ MAX810 do not generate a reset pulse. The graph was generated using a negative-going pulse applied to CC, starting 0.5 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 CC transient can have without causing a reset pulse. As the magnitude of the transient increases (goes farther below the reset threshold), the maximum allowable pulse width decreases. Typically, for the MAX8 L and MAX8 M, a transient that goes 100m below the reset threshold and lasts 20µs or less will not cause a reset pulse. A 0.1µF bypass capacitor mounted as close as possible to the pin provides additional transient immunity. Ensuring a alid Reset Output Down to = 0 When falls below 1, the MAX809 output no longer sinks currentit becomes an open circuit. Therefore, high-impedance CMOS logic inputs connected to can drift to undetermined voltages. This presents no problem in most applications since most µp and other circuitry is inoperative with below 1. However, in applications where must be valid down to 0, adding a pull-down resistor to causes any stray leakage currents to flow to 5 MAX809 R1 100k Figure 2. alid to = Ground Circuit

6 MAX803 INPUT ground, holding low (Figure 2). R1 s value is not critical; 100kΩ is large enough not to load and small enough to pull to ground. A 100kΩ pull-up resistor to is also recommended for the MAX810 if is required to remain valid for CC < 1. Interfacing to µps with Bidirectional Reset Pins Since the output on the MAX803 is open drain, this device interfaces easily with µps that have bidirectional reset pins, such as the Motorola 68HC11. Connecting the µp supervisor s output directly to the microcontroller s (µc s) pin with a single pull-up resistor allows either device to assert reset (Figure 3). MAX803 Open-Drain Output Allows Use with Multiple Supplies Generally, the pull-up connected to the MAX803 will connect to the supply voltage that is being monitored at the IC s pin. However, some systems may use the open-drain output to level-shift from the monitored supply to reset circuitry powered by some other supply (Figure 4). Note that as the MAX803 s decreases below 1, so does the IC s ability to sink current at. Also, with any pull-up, will be pulled high as decays toward 0. The voltage where this occurs depends on the pull-up resistor value and the voltage to which it is connected. µp MOTOROLA 68HCXX Figure 3. Interfacing to µps with Bidirectional Reset I/O MAX803 Benefits of Highly Accurate Reset Threshold Most µp supervisor ICs have reset threshold voltages between 5% and 10% below the value of nominal supply voltages. This ensures a reset will not occur within 5% of the nominal supply, but will occur when the supply is 10% below nominal. When using ICs rated at only the nominal supply ±5%, this leaves a zone of uncertainty where the supply is between 5% and 10% low, and where the reset may or may not be asserted. The MAX8 L/T/Z use highly accurate circuitry to ensure that reset is asserted close to the 5% limit, and long before the supply has declined to 10% below nominal R PULLUP INPUT SYSTEM Figure 4. MAX803 Open-Drain Output Allows Use with Multiple Supplies Chip Information TRANSISTOR COUNT: 275 (SOT23) 380 (SC70)

7 Package Information 7 SC70, 3L.EPS

8 Package Information (continued) 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 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. SOTPO3L.EPS