LTC699IS8#TRPBF

LTC699 Microprocessor Supervisory Circuit U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ Guaranteed Reset Assertion at VCC = 1V 1.5mA Maximum Supply Current SO-8 Packaging 4.65V Precision Voltage Monitor Power OK/Reset Time Delay: 200ms Minimum External Component Count Performance Specified Over Temperature Superior Upgrade for MAX699 The LTC699 provides power supply monitoring for microprocessor-based systems. The features include microprocessor reset and watchdog timing. Precise internal voltage reference and comparator circuit monitor the power supply line. When an out-of-tolerance condition occurs, the RESET output is forced to active low. In addition, the RESET output is guaranteed to remain logic low even with VCC as low as 1V. An internal watchdog timer is also available, which forces the RESET output to active low when the watchdog input is not toggled prior to the time-out period of 1.6 seconds. UO APPLICATI ■ ■ ■ ■ S Critical µP Power Monitoring Intelligent Instruments Computers and Controllers Automotive Systems The LTC699 is offered in DIP and surface mount packages. UO W TYPICAL APPLICATI BLOCK DIAGRA VCC +5V 500k VCC RESET µP POWER RESET µP RESET + C1 µP SYSTEM LTC699 WDI – GND 1.3V I/O LINE GND OSC 0.1µF 0.1µF LTC699 TA1 MICROPROCESSOR RESET AND WATCHDOG TIMING IN A SINGLE CHIP FOR MICROPROCESSOR SYSTEMS. RESET PULSE GENERATOR WDI WATCHDOG TIMER TRANSITION DETECTOR LTC699 BD 1 LTC699 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Notes 1 and 2) Terminal Voltage VCC ................................................... –0.3V to 6.0V WDI Input .............................. – 0.3V to VCC + 0.3V RESET Output ...................................... – 0.3V to 6V Power Dissipation............................................. 500mW Operating Temperature Range LTC699C .............................................. 0°C to 70°C LTC699I ........................................... –40°C to 85°C Storage Temperature Range ................. –65°C to 150°C Lead Temperature (Soldering, 10 sec.)................ 300°C ORDER PART NUMBER TOP VIEW VCC 1 VCC 2 8 GND LTC699 7 RESET GND 3 6 WDI GND 4 5 LTC699CN8 LTC699IN8 NC N8 PACKAGE 8-LEAD PLASTIC DIP TOP VIEW VCC 1 8 GND VCC 2 7 RESET GND 3 6 WDI GND 4 5 NC LTC699 LTC699CS8 LTC699IS8 S8 PACKAGE 8-LEAD PLASTIC SOIC ELECTRICAL CHARACTERISTICS VCC = +5V, TA = 25°C, unless otherwise noted. PARAMETER Operating Voltage Range Supply Current CONDITONS ● MIN 3.0 ● Power Down Reset Assertion Power Up Reset De-Assertion Reset Threshold Hysteresis Reset Active Time ● Watchdog Time-out Period ● WDI Input Current VIL = 0.4, V VIH = 3.5V ISINK = 10µA, VCC = 1V ISINK = 1.6mA, VCC = 4.25V Output Sink Current Logic Low Logic High WDI = VOUT WDI = 0V The ● denotes specifications which apply over the operating temperature range. Note 1: Absolute maximum ratings are those values beyond which the life of device may be impaired. 2 0.6 0.6 4.65 ● ● Reset Active Time PSRR Watchdog Time-out Period PSRR Minimum WDI Input Pulse Width RESET output Voltage at VCC = 1V (Note 3) RESET output Voltage RESET Output Short Circuit Current WDI Input Threshold 4.5 TYP ● 160 140 1.2 1.0 40 200 200 1.6 1.6 1 8 MAX 5.5 1.5 2.5 4.75 4.75 240 280 2.0 2.25 V V mV ms sec 0.8 ms/V ms/V ns mV V mA V 50 µA 200 4 UNITS V mA 200 0.4 25 2.0 ● ● –50 4 –8 Note 2: All voltage values are with respect to GND. Note 3: RESET is active low, open drain output. LTC699 U U U PI FU CTIO S VCC: +5V supply input. The VCC pin should be bypassed with a 0.1µF capacitor. GND: Ground pin. but not serviced prior to the time-out period, the reset pulse generator also forces RESET to active low for a minimum of 140ms for every time-out period (see Figure 2). RESET: Open drain output for µP reset control. When VCC falls below the reset voltage threshold (4.65V typically), RESET goes active low. After VCC returns to 5V, the reset pulse generator forces RESET to remain active low for a minimum of 140ms . When the watchdog timer is enabled WDI: Watchdog Input, WDI, is a three level input. Driving WDI either high or low for longer than the watchdog timeout period forces RESET low. Floating WDI disables the Watchdog Timer. The timer resets itself with each transition of the Watchdog Input (see Figure 2). U W TYPICAL PERFOR A CE CHARACTERISTICS RESET Output Voltage vs Supply Voltage Reset Active Time vs Temperature RESET VOLTAGE THRESHOLD (V) VCC = 5V TA = 25°C EXTERNAL PULLUP = 10µA 224 4 RESET ACTIVE TIME (ms) RESET OUTPUT VOLTAGE (V) 4.66 232 5 3 2 1 0 Reset Voltage Threshold vs Temperature 216 208 200 192 0 1 3 4 2 SUPPLY VOLTAGE (V) 5 184 –50 –25 0 50 75 25 TEMPERATURE (°C) LTC699 G01 4.64 4.63 4.62 4.61 4.60 –50 –25 LTC699 G02 50 25 75 0 TEMPERATURE (°C) 100 125 LTC699 G03 U W U UO APPLICATI 100 125 4.65 S I FOR ATIO Microprocessor Reset The LTC699 uses a bandgap voltage reference and a precision voltage comparator C1 to monitor the 5V supply input VCC (see BLOCK DIAGRAM). When VCC falls below the reset voltage threshold, the RESET output is forced to active low state. The reset voltage threshold accounts for a 5% variation on VCC, so the RESET output becomes active low when VCC falls below 4.65V typical. On powerup, the RESET signal is held active low for a minimum of 140ms after reset voltage threshold is reached to allow the power supply and microprocessor to stabilize. On power- down, the RESET signal remains active low even with VCC as low as 1V. This capability helps hold the microprocessor in stable shutdown condition. Figure 1 shows the timing diagram of the RESET signal. The precision voltage comparator, C1, typically has 40mV of hysteresis which ensures that glitches at VCC pin do not activate the RESET output. Response time is typically 10µs. To help prevent mistriggering due to transient loads, VCC pin should be bypassed with a 0.1µF capacitor with the leads trimmed as short as possible. Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of circuits as described herein will not infringe on existing patent rights. 3 LTC699 W U U UO APPLICATI S I FOR ATIO V2 V2 V1 VCC RESET V1 V1 = RESET VOLTAGE THRESHOLD V2 = RESET VOLTAGE THRESHOLD + RESET THRESHOLD HYSTERESIS t1 t1 t1 = RESET ACTIVE TIME LTC699 F01 Figure 1. Reset Active Time Watchdog Timer The LTC699 provides a watchdog timer function to monitor the activity of the microprocessor. If the microprocessor does not toggle the Watchdog Input (WDI) within the time-out period, RESET is forced to active low for a minimum of 140ms. The watchdog time-out period is fixed at a 1.0 second minimum on the LTC699, which is adequate time for most systems to service the watchdog timer immediately after a reset. Figure 2 shows the timing diagram of watchdog time-out period and reset active time. The watchdog time-out period is restarted as soon as RESET is inactive. When either a high-to-low or low-tohigh transition occurs at the WDI pin prior to time-out, the watchdog time is reset and begins to time out again. To ensure the watchdog time does not time out, either a highto-low or low-to-high transition on the WDI pin must occur at or less than the minimum time-out period. If the input to the WDI pin remains either high or low, reset pulses will be issued every 1.6 seconds typically. The watchdog time can be deactivated by floating the WDI pin. The timer is also disabled when VCC falls below the reset voltage threshold. VCC = 5V WDI t2 t2 t1 RESET t1 t1 LTC699 F02 t1 = RESET ACTIVE TIME t2 = WATCHDOG TIME-OUT PERIOD Figure 2. Watchdog Time-Out Period and Reset Active Time U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic SOIC N8 Package 8-Lead Plastic DIP D D B1 E 8 7 8 6 C A Q1 B α L 1 SYMBOL A A1 B B1 C D E 4 2 3 MILLIMETERS 3.302 ± 0.127 0.508 MIN 0.457 ± 0.076 1.143 – 1.651 0.229 – 0.381 10.160 MAX 7.620 – 8.128 4 N8 1191 e1 INCHES 0.130 ± 0.006 0.020 MIN 0.018 ± 0.003 0.045 – 0.065 0.009 – 0.015 0.400 MAX 0.300 – 0.320 5 e1 E H L A1 S eA 6 A1 A E1 C 7 h × 45° 5 B MILLIMETERS SYMBOL INCHES 0.250 ± 0.010 6.350 ± 0.254 E1 0.325 + 0.025 8.255 + 0.635 eA –0.381 –0.015 0.100 ± 0.010 2.540 ± 0.254 e1 3.175 MIN L 0.125 MIN 1.651 TYP Q1 0.065 TYP S 0.045 ± 0.015 1.143 ± 0.381 TJMAX 110°C Linear Technology Corporation θJA 130°C/W SYMBOL A A1 B C D E INCHES 0.053 – 0.069 0.004 – 0.010 0.014 – 0.019 0.008 – 0.010 0.189 – 0.197 0.150 – 0.157 MILLIMETERS 1.346 – 1.753 0.102 – 0.254 0.356 – 0.483 0.203 – 0.254 4.801 – 5.004 3.810 – 3.988 TJMAX θJA 110°C 180°C/W SYMBOL e H h L α MILLIMETERS INCHES 1.270 TYP 0.050 TYP 0.228 – 0.244 5.791 – 6.198 0.010 – 0.020 0.254 – 0.508 0.016 – 0.050 0.406 – 1.270 0° – 8° TYP 1 2 3 4 S8 1191 CONDITIONS: PCB MOUNT ON FR4 MATERIAL, STILL AIR AT 25°C, COPPER TRACE LT/GP 0192 10K REV 0 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977  LINEAR TECHNOLOGY CORPORATION 1992