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FUJITSU SEMICONDUCTOR
DS04-27401-7E
DATA SHEET
ASSP
Power Supply Monitor
with Watch-Dog Timer
MB3773
n DESCRIPTION
MB3773 generates the reset signal to protect an arbitrary system when the power-supply voltage momentarily is
intercepted or decreased. It is IC for the power-supply voltage watch and “Power on reset” is generated at the
normal return of the power supply. MB3773 sends the microprocessor the reset signal when decreasing more
than the voltage, which the power supply of the system spe
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MB3773 nnnn PIN ASSIGNMENT (FRONT VIEW) C T 1 (TOP VIEW) RESET 2 C T 1 8 RESET 3 CK RESET 2 7 V S GND 4 3 6 CK V REF V CC 5 GND 4 5 V CC V REF 6 7 V S (DIP-8P-M01) (FPT-8P-M01) 8 RESET (SIP-8P-M03) 2
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MB3773 nnnn BLOCK DIAGRAM VCC 5 Reference AMP. : = 1.24 V : = 1.24 V Reference Voltage Generator + VREF 6 : = 100 _ : = 1.2 m A COMP.O kW : = 10 m A + + : = 10 m A _ _ COMP.S + R Q _ VS 7 S : = 40 kW Inhibit Watch CK 3 Dog Timer P.G 4 GND 2 1 8 CT RESET RESET 3
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MB3773 nnnn FUNCTIONAL DESCRIPTIONS Comp.S is comparator including hysteresis. it compare the reference voltage and the voltage of Vs, so that when the voltage of Vs terminal falls below approximately 1.23 V, reset signal outputs. Instantaneous breaks or drops in the power can be detected as abnormal conditions by the MB3773 within a 2 m s interval. However because momentary breaks or drops of this duration do not cause problems in actual systems in some cases, a delayed trigger function can b
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MB3773 • • MB3773 Basic Operation • • VCC VCC Logic Circuit TPR (ms) := 1000 · CT (m F) RESET CT RESET TWD (ms) := 100 · CT (m F) RESET RESET TWR (ms) := 20 · CT (m F) CK CK Example : CT = 0.1 m F GND TRR (ms) : = 100 (ms) TWD (ms) : = 10 (ms) TWR (ms) : = 2 (ms) VCC VSH VSL 0.8 V CK TCK CT TPR RESET TWD TWR TPR (1) (2) (3)(4)(5) (5) (6)(7) (8)(9) (10) (11) (12) 5
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MB3773 nnnn OPERATION SEQUENCE (1) When Vcc rises to about 0.8 V, RESET goes “Low” and RESET goes “High”. The pull-up current of approximately 1 m A (Vcc = 0.8 V) is output from RESET. (2) When Vcc rises to VSH ( : = 4.3V) , the charge with CT starts. At this time, the output is being reset. (3) When CT begins charging, RESET goes “High” and RESET goes “Low”. After TPR reset of the output is released. Reset hold time: TPR (ms) : = 1000 · CT (m F) After releasing reset, the discharge of CT s
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MB3773 nnnn ABSOLUTE MAXIMUM RATINGS Rating Parameter Symbol Unit Min Max Supply voltage VCC - 0.3 + 18 V VS - 0.3 VCC + 0.3 ( £ +18) V Input voltage VCK - 0.3 + 18 V RESET, RESET Supply voltage VOH - 0.3 VCC + 0.3 ( £ +18) V Power dissipation (Ta £ +85 C) PD 200 mW Storage temperature TSTG - 55 + 125 C WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings.
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MB3773 nnnn ELECTORICAL CHARACTERISTICS (1) DC Characteristics (VCC = 5 V, Ta = + 25 C) Value Parameter Symbol Condition Unit Min Typ Max Supply current ICC Watch dog timer operating 600 900 m A VCC 4.10 4.20 4.30 VSL Ta = - 40 C to + 85 C 4.05 4.20 4.35 Detection voltage V VCC 4.20 4.30 4.40 VSH Ta = - 40 C to + 85 C 4.15 4.30 4.45 Hysteresis width VHYS VCC 50 100 150 mV 1.227 1.245 1.263 Reference voltage VREF V Ta = - 40 C to + 85 C 1.215 1.245 1.275 Reference voltage ch
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MB3773 (2)AC Characteristics (VCC = 5 V, Ta = + 25 C) Value Parameter Symbol Condition Unit Min Typ Max 5 V VCC input pulse width TPI 8.0 m s VCC 4 V CK input pulse width TCKW CK 3.0 m s or CK input frequency TCK 20 m s Watch dog timer watching time TWD CT = 0.1 m F 5 10 15 ms Watch dog timer reset time TWR CT = 0.1 mF123ms Rising reset hold time TPR 50 100 150 ms CT = 0.1 m F, VCC RESET, RL = 2.2 kW , TPD1 210 CL = 100 pF Output propagation m s delay time from VCC RESET, RL =
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MB3773 nnnn TYPICAL CHARACTERISTIC CURVES Supply current vs. Supply voltage Output voltage vs. Supply voltage (RESET terminal) 0.75 6.0 Ta = +85 °C Ta = +25 °C Pull up 2.2 kW 0.65 5.0 Ta = - 40 °C, +25 °C, +85 °C Ta = - 40 °C 0.55 4.0 CT = 0.1 μF 0.45 Ta = - 40 °C 3.0 0.35 Ta = +25 °C 2.0 Ta = +85 °C 0.25 1.0 0.15 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Supply voltage VCC (V) Supply voltage VCC (V) Detection voltage Output voltage vs. Supply voltage (VSH,
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MB3773 High level output voltage High level output voltage vs. High level output current vs. High level output current (RESET terminal) (RESET terminal) 5.0 5.0 CT = 0.1 μF CT = 0.1 μF Ta = +25 °C Ta = +25 °C Ta = +85 °C Ta = - 40 °C Ta = - 40 °C 4.5 4.5 Ta = +85 °C 4.0 4.0 0 -5 - 10 - 15 0 -5 - 10 - 15 High level output current IOH8 (m A) High level output current IOH2 (m A) Reference voltage Reference voltage vs. Supply voltage vs. Reference current 1.255 1.246 CT = 0.1 μF Ta = +25 °C
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MB3773 (Continued) Reset time vs. Watchdog timer watching time Temperature vs. Temperature (At watch dog timer) 16 VCC = 5 V VCC = 5 V 3 CT = 0.1 μF CT = 0.1 μF 14 12 2 10 8 1 6 4 0 0 - 40 - 200 20 406080 100 - 40 - 200 20 40 60 80 100 Temperature Ta ( C) Temperature Ta ( C) CT terminal capacitance CT terminal capacitance CT terminal capacitance vs. vs. Reset time vs. Rising reset hold time Watchdog timer watching time (at watch dog timer) 6 6 10 10 2 10 5 5 10 10 4 4 10 10 1 10 3
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MB3773 nnnn APPLICATION CIRCUIT EXAMPLE 1: Monitoring 5V Supply Voltage and Watchdog Timer VCC (5V) MB3773 Logic circuit 8 1 RESET 2 7 RESET 3 6 CK CT 5 GND 4 Notes : • Supply voltage is monitored using VS. • Detection voltage are VSH and VSL. EXAMPLE 2: 5V Supply Voltage Monitoring (external fine-tuning type) VCC (5V) MB3773 R1 Logic circuit 1 8 RESET 2 7 RESET 3 6 CK CT R2 GND 4 5 Notes : • Vs detection voltage can be adjusted externally. • Based on selecting R1 and R2 values that are sufficie
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MB3773 EXAMPLE 3: With Forced Reset (with reset hold) (a) VCC MB3773 Logic circuit 1 8 RESET 2 7 RESET 3 6 CK CT SW GND 4 5 Note : Grounding pin 7 at the time of SW ON sets RESET (pin 8) to Low and RESET (pin 2) to High. (b) VCC MB3773 Logic circuit 1 8 RESET Tr 2 7 RESET 10 kW 3 6 CK Cr GND 4 5 10 kW RESIN Note : Feeding the signal to terminal RESIN and turning on Tr sets the RESET terminal to Low and the RESET terminal to High. 14
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MB3773 EXAMPLE 4: Monitoring Two Supply Voltages (with hysteresis, reset output and NMI) VCC2(12 V) VCC1 (5 V) Logic circuit MB3773 RESET 1 8 2 7 RESET CT 3 6 CK 30 kW 4 5 R3 NMI or port 180 kW GND 10 kW R4 R6 + + _ _ Comp. 1 1.2 kW Comp. 2 R1 4.7 kW 5.1 kW R5 R2 Example : Comp. 1, Comp. 2 : MB4204, MB47393 Notes : • The 5 V supply voltage is monitored by the MB3773. • The 12 V supply voltage is monitored by the external circuit. Its output is connected to the NMI terminal and, when voltage dr
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MB3773 EXAMPLE 5: Monitoring Two Supply Voltages (with hysteresis and reset output) VCC2 (12 V) VCC1 (5 V) 20 kW Logic circuit MB3773 R6 1 8 RESET 2 7 RESET 30 kW Diode CT 3 6 CK R3 GND 4 5 180 kW R4 + + _ _ Comp. 1 1.2 kW Comp. 2 R1 5.1 kW 4.7 kW R2 R5 Example : Comp. 1, Comp. 2 : MB4204, MB47393 Notes : • When either 5 V or 12 V supply voltage decreases below its detection voltage (VSL), the MB3773 RESET terminal is set to High and the MB3773 RESET terminal is set to Low. • Use VCC1 ( = 5 V)
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MB3773 EXAMPLE 6: Monitoring Low voltage and Overvoltage Monitoring (with hysteresis) VCC (5 V) 20 kW MB3773 Logic circuit R6 1 8 RESET 2 7 RESET 30 kW Diode CT 3 6 CK R3 GND 4 5 180 kW R4 + _ _ + Comp. 1 1.2 kW R1 Comp. 2 5.6 kW 4.7 kW R6 R5 Example : Comp. 1, Comp. 2 : MB4204, MB47393 RESET VCC 0 V2L V2H V1L V1H Notes : • Comp. 1 and Comp. 2 are used to monitor for overvoltage while the MB3773 is used to monitor for low voltage. Detection voltages V1L/V1H at the time of low voltage are appro
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MB3773 EXAMPLE 7: Monitoring Supply Voltage Using Delayed Trigger VCC VCC 5V 4V MB3773 Logic circuit 1 8 RESET 2 RESET CT 7 CK 3 6 C1 GND 4 5 Note : Adding voltage such as shown in the figure to VCC increases the minimum input pulse width by 50 m s (C1 = 1000 pF). 18
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MB3773 EXAMPLE 8: Stopping Watch-dog Timer (Monitoring only supply voltage) These are example application circuits in which the MB3773 monitors supply voltage alone without resetting the microprocessor even if the latter, used in standby mode, stops sending the clock pulse to the MB3773. • The watch-dog timer is inhibited by clamping the CT terminal voltage to VREF. The supply voltage is constantly monitored even while the watch-dog timer is inhibited. For this reason, a reset signal is output
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MB3773 (Continued) (c) Using NPN transistor VCC (5 V) MB3773 Logic circuit 1 8 RESET 2 7 RESET R1=1 MW 3 6 CK 4 5 HALT GND R2=1 kW CT (d) Using PNP transistor VCC (5 V) MB3773 Logic circuit 1 8 RESET 2 7 RESET R1=51 kW 3 6 CK 4 5 HALT GND R2=1 kW CT 20
