MB3793-37A
Power Voltage Monitoring IC with
Watchdog Timer Datasheet
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 fall-safe function for various application systems.
The model number is MB3793-37A corresponding to the detected voltage. The model number and package code are as shown
below.
Model No.
MB3793-37A
Marking code
3793AF
Detection voltage
3.7 V
Features
Precise detection of power voltage fall:
2.5%
Detection voltage with hysteresis
Low power dispersion: I
CC
= 30
A
(reference)
Internal dual-input watchdog timer
Watchdog-timer halt function (by inhibition pin)
Independently-set wacthdog and reset times
Two types of packages (SOP-8pin : 2 types)
Application
Arcade Amusement etc
Cypress Semiconductor Corporation
Document Number: 002-08517 Rev. *A
•
198 Champion Court
•
San Jose
,
CA 95134-1709
•
408-943-2600
Revised March 15, 2016
MB3793-37A
Contents
Pin Assignment ................................................................ 3
Pin Description ................................................................. 3
Block Diagram .................................................................. 4
Block Description ............................................................. 5
Absolute Maximum Ratings ............................................ 6
Recommended Operating Conditions ............................ 6
Electrical Characteristics ................................................. 7
DC Characteristics .............................................................. 7
AC Characteristics .............................................................. 8
Diagram ............................................................................. 9
Basic operation (Positive clock pulse) ............................... 9
Basic operation (Negative clock pulse) ........................... 10
Single-clock input monitoring
(Positive clock pulse) ........................................................ 11
Inhibition operation (Positive clock pulse) ........................ 12
Clock pulse input supplementation
(Positive clock pulse) ........................................................ 13
Operation Sequence ....................................................... 13
Typical Characteristics .................................................. 16
Application Example ...................................................... 20
Supply voltage monitor and watchdog timer
(1-clock monitor) ............................................................ 20
Supply voltage monitor and watchdog timer stop ...... 21
Typical Application ......................................................... 22
Notes On Use .................................................................. 23
Ordering Information ...................................................... 23
RoHS Compliance Information of
Lead (Pb) Free version ................................................... 23
Marking Format (Lead Free version) ........................... 24
Labeling Sample (Lead free version) ........................... 25
MB3793-37APF-❏❏❏E1, MB3793-37APNF-❏❏❏E1
Recommended Conditions Of Moisture
Sensitivity Level ............................................................. 26
Package Dimensions ...................................................... 28
Major Changes ................................................................ 30
Document Number: 002-08517 Rev. *A
Page 2 of 29
MB3793-37A
1. Pin Assignment
(Top view)
1
2
3
4
8
7
6
5
CK1
CK2
INH
V
CC
RESET
CTW
CTP
GND
(FPT-8P-M01)
(FPT-8P-M02)
2. Pin Description
Pin no.
1
2
3
4
Symbol
RESET
CTW
CTP
GND
Descriptions
Outputs reset pin
Watchdog timer monitor time setting pin
Power-on reset hold time setting pin
Ground pin
Pin no.
5
6
7
8
Symbol
V
CC
INH
CK2
CK1
Descriptions
Power supply pin
Inhibit pin
Inputs clock 2 pin
Inputs clock 1 pin
Document Number: 002-08517 Rev. *A
Page 3 of 29
MB3793-37A
3. Block Diagram
To V
CC
of all blocks
.
I
1
= 3
μA
.
=
I
2
. .
30
μA
5 V
CC
CTP 3
.
R
1
=
.
494 kΩ
RESET 1
Output circuit
Logic circuit
INH 6
Comp.S
CTW 2
Pulse generator 1
CK1 8
.
V
REF
= 1.24 V
.
R
2
. .
=
240 kΩ
To GND of
all blocks
Watchdog
timer
Reference
voltage
generator
−
+
V
S
Pulse generator 2
CK2 7
4 GND
Document Number: 002-08517 Rev. *A
Page 4 of 29
MB3793-37A
4. Block Description
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 1 and 2. When V
S
falls below 1.24 V, a reset signal is output.
This function enables the MB3793 to detect an abnomality within 1
s
when the power is cut or falls abruptly.
2.
Output circuit
The output circuit contains a RESET output control comparator that compares the voltage at the CTP pin to the threshold voltage to
release the RESET output if the CTP pin voltage exceeds the threshold value.
Since the reset (RESET) output buffer has CMOS organization, no pull-up resistor is needed.
3.
Pulse generator
The pulse generator generates pulses when the voltage at the CK1 and CK2 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.
The logic circuit contains flip-flops.
Flip-flop RSFF1 controls the charging and discharging of the power-on reset hold time setting capacitor (C
TP
).
Flip-flop RSFF2 turns on/off the circuit that accelerates charging of the power-on reset hold time setting capacitor
(C
TP
) at a reset. The RSFF2 operates only at a reset; it does not operate at a power-on reset when the power is turned on.
Document Number: 002-08517 Rev. *A
Page 5 of 29
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