3-Pin, Ultra-Low-Voltage, Low-Power µp Reset Circuits

Transcription

1 ; Rev 1; 6/00 3-Pin, Ultra-Low-oltage, Low-Power General Description The // microprocessor (µp) supervisory circuits monitor the power supplies in 1.8 to 3.3 µp and digital systems. They increase circuit reliability and reduce cost by eliminating external components and adjustments. These devices perform a single function: they assert a reset signal whenever the supply voltage declines below a preset threshold, keeping it asserted for a preset timeout period after has risen above the reset threshold. The only difference among the three devices is their output. The (push/pull) and (open-drain) have an active-low output, while the (push/pull) has an active-high output. The / are guaranteed to be in the correct state for down to 0.7. The is guaranteed to be in the correct state for down to 1.0. The reset comparator in these ICs is designed to ignore fast transients on. Reset thresholds are factorytrimmable between 1.6 and 2.5, in approximately 100m increments. There are 15 standard versions available (2,500 piece minimum-order quantity); contact the factory for availability of nonstandard versions (10,000 piece minimum-order quantity). For space-critical applications, the // come packaged in a 3-pin SOT23. Pentium II Computers Computers Controllers Intelligent Instruments Critical µp/µc Power Monitoring Portable/Battery-Powered Equipment Automotive Applications Typical Operating Circuit and Pin Configuration appear at end of data sheet. Selector Guide appears at end of data sheet. Pentium II is a trademark of Intel Corp. Features Ultra-Low 0.7 Operating Supply oltage Low 3.3µA Supply Current Precision Monitoring of 1.8 and 2.5 Power- Supply oltages Reset Thresholds Available from 1.6 to 2.5, in Approximately 100m Increments Fully Specified over Temperature Three Power-On Reset Pulse Widths Available (1ms min, 20ms min, 100ms min) Low Cost Three Available Output Structures: Push/Pull, Push/Pull, Open-Drain Guaranteed / alid to = 0.7 (/) Power-Supply Transient Immunity No External Components 3-Pin SOT23 Package Pin Compatible with MAX809/MAX810 and MAX6326/MAX6327/MAX6328 PART* UR D_-T UR D_-T UR D_-T Ordering Information TEMP. RANGE -40 C to +125 C -40 C to +125 C -40 C to +125 C PIN-PACKAGE 3 SOT SOT SOT23-3 * These devices are available in factory-set reset thresholds from 1.6 to 2.5, in approximately 0.1 increments. Choose the desired reset threshold suffix from Table 1 and insert it in the blanks following UR in the part number. Factory-programmed reset timeout periods are also available. Insert the number corresponding to the desired nominal reset timeout period (1 = 1ms min, 2 = 20ms min, 3 = 100ms min) in the blank following D in the part number. There are 15 standard versions with a required order increment of 2500 pieces. Sample stock is generally held on the standard versions only (see Selector Guide). Contact the factory for availability of nonstandard versions (required order increment is 10,000 pieces). All devices available in tape-and-reel only. // Maxim Integrated Products 1 For free samples and the latest literature, visit or phone For small orders, phone

2 3-Pin, Ultra-Low-oltage, Low-Power // ABSOLUTE MAXIMUM RATINGS Terminal oltage (with respect to ) to +6 Push/Pull, to ( + 0.3) Open-Drain to +6 Input Current ( )...20mA Output Current (, )...20mA Continuous Power Dissipation (T A = +70 C) SOT23-3 (derate 4mW/ C above +70 C)...320mW Operating Temperature Range C to +125 C Storage Temperature Range C to +160 C Lead Temperature (soldering, 10s) 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 ( = full range, T A = -40 C to +125 C, unless otherwise noted. Typical values are at and = 3, reset not assert- PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS T A = 0 C to +85 C / Supply oltage Range T A = -40 C to +85 C / Supply Current I CC No load T A = -40 C to +125 C Reset Threshold TH MAX633_UR D_-T, Table 1 / = = TH - TH + TH 1.8% 1.8% T A = -40 C to +125 C TH - TH + TH 3% 3% Reset Active Timeout Period t RP Falling Reset Delay falling at 10/ms 24 µs MAX633_UR D1-T MAX633_UR D2-T ms MAX633_UR D3-T µa Output Low oltage (/) Output High oltage () Output oltage () Output Leakage Current () Reset I SINK = 50µA, OL asserted I SINK = 500µA, OH Reset not I SOURCE = 200µA, asserted I SOURCE = 500µA, OH Reset I SOURCE = 1µA, asserted I SOURCE = 200µA, OL Reset not I SINK = 500µA, asserted I SINK = 1.2mA, > TH, deasserted 0.5 µa 2

3 3-Pin, Ultra-Low-oltage, Low-Power (Reset not asserted,, unless otherwise noted.) ICC (µa) OUTPUT OLTAGE HIGH (CC - OH) (m) SUPPLY CURRENT vs. TEMPERATURE = 2.5 = NOT ASSERTED /33/34 toc TEMPERATURE ( C) OUTPUT OLTAGE HIGH vs. SUPPLY OLTAGE T A = +85 C TH = 2.2 ISOURCE = 100µA ASSERTED T A = -40 C () /33/34 toc-5 NORMALIZED TIMEOUT PERIOD MAXIMUM TRANSIENT DURATION (µs) NORMALIZED TIMEOUT PERIOD vs. TEMPERATURE TH = TEMPERATURE ( C) MAXIMUM TRANSIENT DURATION vs. COMPARATOR OERDRIE DOES NOT OCCUR OCCURS COMPARATOR OERDRIE (m) Typical Operating Characteristics /33/34-2 /33/34 toc-4 OUTPUT OLTAGE LOW (m) PROPAGATION DELAY (µs) () OUTPUT OLTAGE LOW vs. SUPPLY OLTAGE T A = -40 C TH = 2.5 I SINK = 500µA ASSERTED T A = +85 C FALLING PROPAGATION DELAY vs. TEMPERATURE FALLING AT 1/ms FALLING AT 10/ms TEMPERATURE ( C) Pin Description /33/34 toc-6 /33/34 toc-3 // PIN 1 1 NAME Ground FUNCTION 2 2 Active-Low Reset Output. remains low while is below the reset threshold and for a reset timeout period (t RP ) after rises above the reset threshold. on the is open-drain. Active-High Reset Output. remains high while is below the reset threshold and for a reset timeout period (t RP ) after rises above the reset threshold. 3 3 Supply oltage (0.7 to 5.5) 3

4 3-Pin, Ultra-Low-oltage, Low-Power // Applications Information Interfacing to µps with Bidirectional Reset Pins Since the output on the 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 1). Negative-Going CC Transients In addition to issuing a reset to the µp during power-up, power-down, and brownout conditions, these devices are relatively immune to short-duration, negative-going transients (glitches). The Typical Operating Characteristics show the Maximum Transient Duration vs. Reset Comparator Overdrive graph. The graph shows the maximum pulse width that a negative-going transient may typically have without issuing a reset signal. As the amplitude of the transient increases, the maximum allowable pulse width decreases. Ensuring a alid Reset Output Down to = 0 When falls below 1 and approaches the minimum operating voltage of 0.7, push/pull-structured reset sinking (or sourcing) capabilities decrease drastically. High-impedance CMOS-logic inputs connected to the pin can drift to indeterminate voltages. This does not present a problem in most cases, since most µps and circuitry do not operate at below 1. For the, where must be valid down to 0, adding a pull-down resistor between and removes stray leakage currents, holding low (Figure 2a). The pull-down resistor value is not critical; 100kΩ is large enough not to load and small enough to pull it low. For the, where must be valid to = 0, a 100kΩ pull-up resistor between and will hold high when falls below 0.7 (Figure 2b). Since the has an open-drain, active-low output, it typically uses a pull-up resistor. With this device, will most likely not maintain an active condition, but will drift to a non-active level due to the pull-up resistor and the reduced sinking capability of the opendrain device. Therefore, this device is not recommended for applications where the pin is required to be valid down to = 0. MOTOROLA 68HCXX INPUT Figure 1. Interfacing to µps with Bidirectional Reset Pins (a) - THRESHOLD SUFFIX 100k Figure 2. Ensuring Reset alid Down to = 0 Table 1. Factory-Trimmed Reset Thresholds* * Factory-trimmed reset thresholds are available in approximately 100m increments, with a ±1.8% room-temperature variance. µp T A = -40 C to +125 C MIN TYP MAX MIN MAX MAX633_UR25D_ MAX633_UR24D_ MAX633_UR23D_ MAX633_UR22D_ MAX633_UR21D_ MAX633_UR20D_ MAX633_UR19D_ MAX633_UR18D_ MAX633_UR17D_ MAX633_UR16D_ (b) *ASSUMES HIGH-Z INPUT TO THE µp 100k* 4

5 3-Pin, Ultra-Low-oltage, Low-Power TOP IEW () 1 2 ( ) ARE FOR Pin Configuration SOT PART OUTPUT STAGE NOMINAL TH () () Selector Guide (Standard ersions*) MINIMUM TIMEOUT (ms) SOT TOP MARK UR23D3-T Push/Pull FZDM UR22D3-T Push/Pull FZCN UR20D3-T Push/Pull FZDL UR18D3-T Push/Pull FZCM UR16D3-T Push/Pull FZCL UR23D3-T Push/Pull FZCS UR22D3-T Push/Pull FZCR UR20D3-T Push/Pull FZCQ UR18D3-T Push/Pull FZCP UR16D3-T Push/Pull FZCO UR23D3-T Open-Drain FZDO UR22D3-T Open-Drain FZC UR20D3-T Open-Drain FZDN UR18D3-T Open-Drain FZCU UR16D3-T Open-Drain FZCT ( ) ARE FOR Typical Operating Circuit INPUT µp // * Sample stock is generally held on all standard versions. 5

6 3-Pin, Ultra-Low-oltage, Low-Power // TRANSISTOR COUNT: 505 Chip Information Package Information SOTPO3L.EPS 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. 6 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.