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Supply Monitor. MB3771 Datasheet

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Supply Monitor. MB3771 Datasheet
















MB3771 Monitor. Datasheet pdf. Equivalent













Part

MB3771

Description

Power Supply Monitor



Feature


FUJITSU SEMICONDUCTOR DATA SHEET DS04-2 7400-7E ASSP For power supply applicat ions BIPOLAR Power Supply Monitor MB3 771 s DESCRIPTION The Fujitsu MB3771 is designed to monitor the voltage level of one or two power supplies (+5 V and an arbitrary voltage) in a microprocess or circuit, memory board in large-size computer, for example. If the circuit s power supply devi.
Manufacture

Fujitsu

Datasheet
Download MB3771 Datasheet


Fujitsu MB3771

MB3771; ates more than a specified amount, then the MB3771 generates a reset signal to the microprocessor. Thus, the computer data is protected from accidental erasu re. Using the MB3771 requires few exter nal components. To monitor only a +5 V supply, the MB3771 requires the connect ion of one external capacitor. The leve l of an arbitrary detection voltage is determined by two .


Fujitsu MB3771

external resistors. The MB3771 is availa ble in an 8-pin Dual In-Line, Single In -Line Package or space saving Flat Pack age. s FEATURES • • • • • • • • Precision voltage detecti on (VSA = 4.2 V ± 2.5 %) User selectab le threshold level with hysterisis (VSB = 1.23 V ± 1.5 %) Monitors the voltag e of one or two power supplies (5 V and an arbitrary voltage, >1.23 V) Usable.


Fujitsu MB3771

as over voltage detector Low voltage ou tput for reset signal (VCC = 0.8 V typ. ) Minimal number of external components (one capacitor min.) Low power dissipa tion (ICC = 0.35 mA typ., VCC = 5 V) De tection threshold voltage has hysteresi s function Reference voltage is connect able. s PACKAGES 8-pin plastic DIP 8-p in plastic SIP 8-pin plastic SOIP (DIP -8P-M01) (SIP-8P-.





Part

MB3771

Description

Power Supply Monitor



Feature


FUJITSU SEMICONDUCTOR DATA SHEET DS04-2 7400-7E ASSP For power supply applicat ions BIPOLAR Power Supply Monitor MB3 771 s DESCRIPTION The Fujitsu MB3771 is designed to monitor the voltage level of one or two power supplies (+5 V and an arbitrary voltage) in a microprocess or circuit, memory board in large-size computer, for example. If the circuit s power supply devi.
Manufacture

Fujitsu

Datasheet
Download MB3771 Datasheet




 MB3771
FUJITSU SEMICONDUCTOR
DATA SHEET
DS04-27400-7E
ASSP For power supply applications
BIPOLAR
Power Supply Monitor
MB3771
s DESCRIPTION
The Fujitsu MB3771 is designed to monitor the voltage level of one or two power supplies (+5 V and an arbitrary
voltage) in a microprocessor circuit, memory board in large-size computer, for example.
If the circuit’s power supply deviates more than a specified amount, then the MB3771 generates a reset signal to
the microprocessor. Thus, the computer data is protected from accidental erasure.
Using the MB3771 requires few external components. To monitor only a +5 V supply, the MB3771 requires the
connection of one external capacitor. The level of an arbitrary detection voltage is determined by two external
resistors. The MB3771 is available in an 8-pin Dual In-Line, Single In-Line Package or space saving Flat Package.
s FEATURES
• Precision voltage detection (VSA = 4.2 V ± 2.5 %)
• User selectable threshold level with hysterisis (VSB = 1.23 V ± 1.5 %)
• Monitors the voltage of one or two power supplies (5 V and an arbitrary voltage, >1.23 V)
• Usable as over voltage detector
• Low voltage output for reset signal (VCC = 0.8 V typ.)
• Minimal number of external components (one capacitor min.)
• Low power dissipation (ICC = 0.35 mA typ., VCC = 5 V)
• Detection threshold voltage has hysteresis function
• Reference voltage is connectable.
s PACKAGES
8-pin plastic DIP
8-pin plastic SIP
8-pin plastic SOIP
(DIP-8P-M01)
(SIP-8P-M03)
(FPT-8P-M01)




 MB3771
MB3771
s PIN ASSIGNMENT
CT
VSC
OUTC
GND
(TOP VIEW)
18
27
36
45
RESET
VSA
VSB /RESIN
VCC
(DIP-8P-M01)
(FPT-8P-M01)
(FRONT VIEW)
8
7
6
5
4
3
2
1
RESET
VSA
VSB / RESIN
VCC
GND
OUTC
VSC
CT
(SIP-8P-M03)
s BLOCK DIAGRAM
VSA 7
100 k
40 k
VSB / RESIN 6
+
Comp. A
1.24 V
+
Comp. B
VCC
5
REFERENCE VOLTAGE
1.24 V
+
RQ
12 µA
−+
10 µA
Comp. C
2 VSC
+
S
1
CT
83
RESET OUTC
4 GND
2




 MB3771
MB3771
s FUNCTIONAL DESCRIPTIONS
Comparators Comp.A and Comp.B apply a hysteresis to the detected voltage, so that when the voltage at either
the VSA or VSB pin falls below 1.23 V the RESET output signal goes to “low” level.
Comp. B may be used to detect any given voltage(Sample Application 3), and can also be used as a forced
reset pin (with reset hold time) with TTL input (Sample Application 6).
Note that if Comp.B is not used, the VSB pin should be connected to the VCC pin (Sample Application 1).
Instantaneous breaks or drops in the power supply can be detected as abnormal conditions by the MB3771
within a 2 µs 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 be created by connecting capacitors to the VSA or
VSB pin (Sample Application 8).
Because the RESET output has built-in pull-up resistance, there is no need to connect to external pull-up
resistance when connected to a high impedance load such as a CMOS logic IC.
Comparator Comp. C is an open-collector output comparator without hysteresis, in which the polarity of input/
output characteristics is reversed. Thus Comp. C is useful for over-voltage detection (Sample Application 11)
and positive logic RESET signal output (Sample Application 7), as well as for creating a reference voltage
(Sample Application 10).
Note that if Comp. C is not used, the VSC pin should be connected to the GND pin (Sample Application 1).
s FUNCTION EXPLANATION
VCC
18
CT 2 7
36
45
VS
VCC
0.8 V
RESET
RESET
VHYS
TPO
TPO
(1) (2) (3) (4) (5) (6)
(7) (8)
t
t
(1) When VCC rises to about 0.8V, RESET goes low.
(2) When VCC reaches VS +VHYS, CT then begins charging. RESET remains low during this time
(3) RESET goes high when CT begins charging.
TPO =: CT × 10 5 (Refer to CT pin capacitance vs. hold time )
(4) When VCC level dropps lower then VS, then RESET goes low and CT starts discharging.
(5) When VCC level reaches VS + VHYS, then CT starts charging.
In the case of voltage sagging, if the period from the time VCC goes lower than or equal to VS to the time VCC
reaches VS +VHYS again, is longer than tPI, (as specified in the AC Characteristics), CT is discharged and charged
successively.
(6) After TPO passes, and VCC level exceeds VS + VHYS, then RESET goes high.
(7) Same as Point 4.
(8) RESET remains low until VCC drops below 0.8V.
3




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