MB3793-45
Power-Voltage Monitoring IC with
Watchdog Timer Datasheet
Description
The MB3793 is an integrated circuit to monitor power voltage; it incorporates a watchdog timer. A reset signal is output when the
power is cut or falls abruptly. When the power recovers normally after resetting, a power-on reset signal is output to microprocessor
units (MPUs). An internal watchdog timer with two inputs for system operation diagnosis can provide a fail-safe function for various
application systems.
Model No.
MB3793-45
Marking Code
3793-7
Detection Voltage
4.5 V
Features
•
•
•
•
•
•
Precise detection of power voltage fall:
±2.5%
Detection voltage with hysteresis
Low power dispersion: I
CC
= 31
μA
(reference)
Internal dual-input watchdog timer
Watchdog timer halt function (by inhibition pin)
Independently-set watchdog and reset times
Application
• Arcade Amusement etc.
Cypress Semiconductor Corporation
Document Number: 002-08552 Rev. *C
•
198 Champion Court
•
San Jose
,
CA 95134-1709
•
408-943-2600
Revised June 29, 2017
MB3793-45
Contents
Description ................................................................... 1
Features ....................................................................... 1
Application ................................................................... 1
1. Pin Assignment ...................................................... 3
2. Pin Description ....................................................... 3
3. Block Diagram ........................................................ 4
4. Block Functions ..................................................... 5
5. Absolute Maximum Ratings .................................. 6
6. Recommended Operating Conditions .................. 6
7. Electrical Characteristics ...................................... 7
7.1 DC Characteristics ........................................... 7
7.2 AC Characteristics ........................................... 7
8. Timing Diagram ...................................................... 8
8.1 Basic Operation (Positive Clock Pulse) ........... 8
8.2 Basic Operation (Negative Clock Pulse) .......... 9
8.3 Single-Clock Input Monitoring (Positive Clock
Pulse) .................................................................... 10
8.4 Inhibition Operation (Positive Clock Pulse)..... 11
8.5 Clock Pulse Input Supplementation (Positive
Clock Pulse) .......................................................... 12
9. Operation Sequence ............................................ 13
10. Typical Characteristics ...................................... 15
11. Application Example .......................................... 18
11.1 Supply Voltage Monitor and Watchdog Timer18
11.2 Supply Voltage Monitor and Watchdog Timer
Stop ...................................................................... 19
11.3 Setting of Compulsory Reset ....................... 19
12. Usage Precaution ............................................... 20
13. Ordering Information ......................................... 20
14. RoHS Compliance Information ......................... 20
15. Package Dimensions ......................................... 21
16. Major Changes ................................................... 23
Sales, Solutions, and Legal Information ................. 24
Document Number: 002-08552 Rev. *C
Page 2 of 24
MB3793-45
4. Block Functions
1.
Comp. S
Comp. S is a comparator with hysteresis to compare the reference voltage with a voltage (V
S
) that is the result of dividing the power
voltage (V
CC
) by resistors R
1
and R
2
. When V
S
falls below 1.24 V, a reset signal is output. This function enables the MB3793 to detect
an abnormality within 1
μs
when the power is cut or falls abruptly.
2.
Output Circuit
The output circuit has a comparator to control the reset signal (RESET) output. When the voltage at the CTP pin for setting the
power-on reset hold time exceeds the threshold voltage, resetting is canceled.
Since the reset (RESET) output buffer has the CMOS organization, no pull-up resistor is needed.
3.
Pulse Generator
The pulse generator generates pulses when the voltage at the CK1 and CK2 input clock pins changes to High from Low level
(positive-edge trigger) and exceeds the threshold voltage; it sends the clock signal to the watchdog timer.
4.
5.
6.
Watchdog Timer
Inhibition Pin
Logic Circuit
The watchdog timer can monitor two clock pulses. Short-circuit the CK1 and CK2 clock pins to monitor a single clock pulse.
The inhibition (INH) pin forces the watchdog timer on/off. When this pin is High level, the watchdog timer is stopped.
Logic circuit controls charging and discharging of the power-on reset hold time setting capacity (C
TP
) on a signal of Comp.S and
Watchdog timer.
Document Number: 002-08552 Rev. *C
Page 5 of 24
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