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MB3771 Dataheets PDF



Part Number MB3771
Manufacturers Fujitsu
Logo Fujitsu
Description Power Supply Monitor
Datasheet MB3771 DatasheetMB3771 Datasheet (PDF)

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 prot.

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


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