LTC1232CS8#TRPBF

LTC1232 Microprocessor Supervisory Circuits U FEATURES ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®1232 provides power supply monitoring, watchdog timing and external reset for microprocessor systems. A precise internal voltage reference and comparator circuit monitor the power supply line. When an out-of-tolerance condition occurs, the reset outputs are forced to active states. The RST output is guaranteed to remain logic low even with VCC as low as 1V. Guaranteed Reset Assertion at VCC = 1V 8-Pin SO Plastic Package 2.0mA Maximum Supply Current 4.62V/4.37V Precision Voltage Monitor Power OK/Reset Time Delay: 600ms Minimum External Component Count Superior Upgrade for DS1232 The LTC1232 has an internal watchdog timer which forces the reset outputs to active states when the Strobe input is not forced low prior to a preset time-out period. The watchdog timing can be set to operate on time-out periods of typically 150ms, 600ms or 1.2 seconds. U APPLICATIO S ■ ■ ■ ■ Critical µP Power Monitoring Intelligent Instruments Computers and Controllers Automotive Systems The LTC1232 performs push-button reset control. The LTC1232 debounces the push-button input and guarantees an active reset pulse width of 250ms minimum. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO RST Output Voltage vs Supply Voltage 5 PB RST MPU (e.g. 6805) VCC 100k 5V DC ST TD I/O LINE LTC1232 TOL RST GND RST RESET LTC1232 • TA01 RST OUTPUT VOLTAGE (V) 5V DC 4 3 2 1 0 0 1 3 4 2 SUPPLY VOLTAGE (V) 5 LTC1232 • TA02 sn1232 1232fas 1 LTC1232 W W W AXI U U U W PACKAGE/ORDER I FOR ATIO U ABSOLUTE RATI GS (Note 1, 2 and 3) Terminal Voltage VCC ....................................................... –0.3V to 7.0V ST and RST .......................................... –0.3V to 7.0V All Other Inputs and Outputs ...... –0.3V to VCC +0.3V Power Dissipation .............................................. 500mW Operating Temperature Range LTC1232C ............................................... 0°C to 70°C LTC1232I ........................................... –40°C to 85°C Storage Temperature Range ................. –65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C TOP VIEW PB RST 1 8 VCC TD 2 7 ST TOL 3 6 RST GND 4 5 RST ORDER PART NUMBER LTC1232CN8 N8 PACKAGE 8-LEAD PDIP TJMAX = 100°C, θJA = 130°C/W ORDER PART NUMBER TOP VIEW PB RST 1 8 VCC TD 2 7 ST TOL 3 6 RST GND 4 5 RST LTC1232CS8 LTC1232IS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 100°C, θJA = 180°C/W 1232 1232I Consult LTC Marketing for parts specified with wider operating temperature ranges. U PRODUCT SELECTIO GUIDE BATTERY BACKUP POWER FAIL WARNING RAM WRITE PROTECT PINS RESET WATCHDOG TIMER LTC1232 8 X X LTC690 8 X X X X LTC691 16 X X X X LTC694 8 X X X X LTC695 16 X X X X X LTC699 8 X X LTC1235 16 X X X X X PUSH-BUTTON RESET CONDITIONAL BATTERY BACKUP X X X X sn1232 1232fas 2 LTC1232 U U U U WW RECO E DED OPERATI G CO DITIO S The ● denotes the specifications which apply over the full operating temperature. VCC = full operating range. SYMBOL PARAMETER VCC Supply Voltage VIH VIL CONDITIONS MIN TYP MAX UNITS ● 4.5 5 5.5 V ST and PB RST Input High Level ● 2 VCC +0.3 V ST and PB RST Input Low Level ● –0.3 0.8 V DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature. VCC = full operating range. SYMBOL PARAMETER CONDITIONS IIL Input Leakage (Note 3) ● –1 IOH Output Current at 2.4V (Note 5) ● –1 –13 mA IOL Output Current at 0.4V (Note 5) ● 2 6 mA ICC Supply Current (Note 4) ● VCCTP VCC Trip Point TOL = GND ● VCCTP VCC Trip Point TOL = VCC ● VHYS VCC Trip Point Hysteresis VRST RST Output Voltage at VCC = 1V AC CHARACTERISTICS MIN TYP MAX 1 UNITS µA 0.5 2 4.5 4.62 4.74 V 4.25 4.37 4.49 V 40 ISINK = 10µA 4 mA mV 200 mV The ● denotes the specifications which apply over the full operating temperature. VCC = full operating range. SYMBOL PARAMETER CONDITIONS tPB PB RST = VIL ● 40 tRST RESET Active Time ● 250 tST ST Pulse Width ● 20 tRPD VCC Detect to RST and RST ● tf VCC Slew Rate 4.75V–4.25V ● 300 tRPU VCC Detect to RST and RST (Reset Active Time) ● 250 tR VCC Slew Rate 4.25V–4.75V ● 0 tTD ST Pin Detect to RST and RST (Watchdog Time-Out Period) ● ● ● 60 250 500 CIN Input Capacitance 5 pF COUT Output Capacitance 5 pF tR = 5µs TD = GND TD = Floating TD = VCC Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All voltage values are with respect to GND. Note 3: The PB RST pin is internally pulled up to VCC with an internal impedance of 10k typical. The TD pin has internal bias current. MIN TYP MAX UNITS ms 610 1000 ms ns 100 ns µs 610 1000 ms ns 150 610 1200 250 1000 2000 ms ms ms Note 4: Measured with outputs open. Note 5: The RST pin is an open drain output. sn1232 1232fas 3 LTC1232 WU W TI I G DIAGRA S Push-Button Reset PB RST Power Down tF VIH VIL tPB VCC tRST RST 4.50V tRPD VIH VIL RST 4.75V 4.25V RST LTC1232 • TD01 VOH VOL RST LTC1232 • TD03 Strobe Input Power Up tR tST VCC 4.50V 4.75V 4.25V tRPU tTD LTC1232 • TD02 RST VOH VOL RST LTC1232 • TD04 W BLOCK DIAGRA VCC 8 TOL 3 6 RST 5 RST + 5%, 10% SWITCH RESET PULSE GENERATOR C1 – 1.3V OSC PB RST 1 LEVEL SENSE AND DEBOUNCE ST 7 LEVEL SENSE TD 2 TIME-OUT SELECTION WATCHDOG TIMER LTC1232 • BD01 sn1232 1232fas 4 LTC1232 U W TYPICAL PERFOR A CE CHARACTERISTICS VCC Trip Point vs Temperature VCC Trip Point vs Temperature 4.63 VCC = 5V TOL = VCC TOL = GND 672 4.61 4.60 4.59 4.58 RESET ACTIVE TIME (ms) 4.37 VCC TRIP POINT (V) 4.62 VCC TRIP POINT (V) Reset Active Time vs Temperature 696 4.38 4.36 4.35 4.34 50 25 75 0 TEMPERATURE (˚C) 100 125 4.32 –50 –25 50 25 75 0 TEMPERATURE (˚C) LTC1232 • TPC01 600 100 552 –50 –25 125 50 25 75 0 TEMPERATURE (˚C) Time-Out Period vs Temperature 100 125 LTC1232 • TPC03 LTC1232 • TPC02 RST Output Voltage vs Supply Voltage 5 696 VCC = 5V TD = NO CONNECTION TA = 25°C EXTERNAL PULL-UP = 10µA 672 RST OUTPUT VOLTAGE (V) WATCHDOG TIME-OUT PERIOD (ms) 624 576 4.33 4.57 –50 –25 648 648 624 600 576 552 –50 –25 4 3 2 1 0 50 25 75 0 TEMPERATURE (˚C) 100 125 LTC1232 • TPC04 0 1 3 4 2 SUPPLY VOLTAGE (V) 5 LTC1232 • TPC05 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. PB RST: Logic Input to be Directly Connected to a PushButton. The PB RST input requires an active low signal which is debounced and timed for a minimum of 40ms. When this condition is satisfied, the reset pulse generator forces the reset outputs to active states. The reset outputs remain in active states for a minimum of 250ms after PB RST is released from logic low level. TOL: Input to Select 5% or 10% Variation on VCC. When TOL is connected to GND, the reset pulse generator forces the reset outputs to active states as VCC falls below 4.75V (4.62V typical). When TOL is connected to VCC, the reset pulse generator forces the reset outputs to active states as VCC falls below 4.5V (4.37V typical). TD: Time-Out Delay. TD is a three-level input to select three different time-out periods. The time-out period is set by the TD input to be 150ms with TD connected to GND, 600ms with TD left floating, and 1.2 seconds with TD connected to VCC. sn1232 1232fas 5 LTC1232 U U U PI FU CTIO S active low for a minimum of 250ms from the moment the push-button reset input is released from logic low level. RST: Open Drain Logic Output for µP Reset Control. The LTC1232 provides three ways to generate µP reset. First, when VCC falls below VCC trip point (4.75V with TOL = GND and 4.5V with TOL = VCC), RST goes active low. After VCC returns to 5V, the reset pulse generator forces RST to remain active low for a minimum of 250ms. Second, when the watchdog timer is not serviced prior to a selected time-out period, the reset pulse generator also forces RST to active low for a minimum of 250ms and repeats for every time-out period. Third and the last, when the PB RST pin stays active low for a minimum of 40ms, RST becomes active low. The RST output will remain RST: RST is an Active High Logic Output. It is the inverse of RST. ST: Logic Input to Reset the Watchdog Timer. Driving ST either high or low longer than the time-out period set by the TD input, forces the reset outputs to active states for a minimum of 250ms. The timer resets itself and begins to time-out again with each high to low transition on the ST input (see Figure 2). U W U U APPLICATIO S I FOR ATIO Power Monitoring The LTC1232 uses a bandgap voltage reference and a precision voltage comparator, C1, to monitor the 5V supply input on VCC (see Block Diagram). When VCC falls below the V CC trip point (4.62V typical with TOL = GND and 4.37V typical with TOL VCC), the reset outputs are forced to active states. The VCC trip point accounts for a 5% or 10% variation on VCC, so the reset outputs become active when VCC falls below the VCC trip point. On power-up, the reset signals are held in active states for a minimum of 250ms after the VCC trip point is reached to allow the power supply and microprocessor to stabilize. On power-down, the RST 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 RST signal. V2 VCC The precision voltage comparator, C1, typically has 40mV of hysteresis which ensures that glitches at VCC pin do not activate the reset outputs. Response time is typically 10µs. To help prevent mitriggering due to transient loads, VCC pin should be bypassed with a 0.1µF capacitor with the leads trimmed as short as possible. Push-Button Reset The LTC1232 provides a logic input pin, PB RST, for direct connection to a push-button. This push-button reset input requires an active low signal. Internally, this input signal is debounced and timed for a minimum of 40ms. When this V2 V1 t1 V1 t1 RST V1 = VCC TRIP POINT V2 = VCC TRIP POINT + VHYS t1 = RESET ACTIVE TIME LTC1232 • TA03 Figure 1. Reset Active Time sn1232 1232fas 6 LTC1232 U W U U APPLICATIO S I FOR ATIO condition is satisfied, the reset pulse generator forces the reset outputs to active states. The reset signals will remain active for a minimum of 250ms from the moment the push-button reset input is released from logic low level (see Timing Diagram). VCC = 5V ST t1 t1 t2 t2 t1 RST t1 = RESET ACTIVE TIME t2 = WATCHDOG TIME-OUT PERIOD Watchdog Timer LTC1232 • TA04 The LTC1232 provides a watchdog timer function to monitor the activity of the microprocessor. If the microprocessor does not stimulate the strobe input, ST, within a selected time-out period, the reset outputs are forced to active states for a minimum of 250ms. The time-out period is selected by the Time-Out Delay input, TD, to be 150ms with TD connected to GND, 600ms with TD left floating, and 1.2 seconds with TD connected to VCC. The 1.2 second time-out period is adequate for many systems to serve 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 Figure 2. Watchdog Time-Out Period and Reset Active Time soon as the reset outputs are inactive. When a high-to-low transition occurs at the ST 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, a high-to low transition on the ST pin must occur at or less than the minimum time-out period. If the input to the ST pin remains either high or low, reset pulses will be issued for every time-out period selected by the TD pin. The watchdog timer is disabled when VCC falls below the VCC trip point. U PACKAGE DESCRIPTIO N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 1 2 3 4 .255 ± .015* (6.477 ± 0.381) .300 – .325 (7.620 – 8.255) .009 – .015 (0.229 – 0.381) +.035 .325 –.015 ( 8.255 +0.889 –0.381 ) .045 – .065 (1.143 – 1.651) .130 ± .005 (3.302 ± 0.127) .065 (1.651) TYP .100 (2.54) BSC .125 (3.175) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 0502 NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) sn1232 1232fas 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 its circuits as described herein will not infringe on existing patent rights. 7 LTC1232 U PACKAGE DESCRIPTIO S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 7 6 5 N N .245 MIN .160 ±.005 1 .030 ±.005 TYP .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 1 2 .053 – .069 (1.346 – 1.752) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN .014 – .019 (0.355 – 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 3 4 .004 – .010 (0.101 – 0.254) .050 (1.270) BSC SO8 0502 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65V Threshold LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.9V Threshold LTC699 5V Supply Monitor and Watchdog Timer 4.65V Threshold LTC1326 Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ 4.725V, 3.118V, 1V Thresholds (±0.75%) LTC1326-2.5 Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%) LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI tFAIL Timing Specifications LTC1726-2.5 Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ Adjustable RESET and Watchdog Time-Outs LTC1726-5 Micropower Triple Supply Monitor for 5V, 3.3V and ADJ Adjustable RESET and Watchdog Time-Outs LTC1727-2.5/LTC1727-5 Micropower Triple Supply Monitor with Open-Drain Reset Individual Monitor Outputs in MSOP LTC1728-1.8/TC1728-3.3 Micropower Triple Supply Monitor with Open-Drain Reset 5-Lead SOT-23 Package LTC1728-2.5/LTC1728-5 Micropower Triple Supply Monitor with Open-Drain Reset 5-Lead SOT-23 Package LTC1985-1.8 Micropower Triple Supply Monitor with Push-Pull Reset Output 5-Lead SOT-23 Package sn1232 1232fas 8 Linear Technology Corporation LW/TP 1002 1K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1992