MB3773 View Datasheet(PDF) - Cypress Semiconductor

Part Name

Description

Manufacturer

MB3773

Power Supply Monitor with Watch-Dog Timer

Cypress Semiconductor 

MB3773

EXAMPLE 4: Monitoring Two Supply Voltages (with hysteresis, reset output and NMI)

VCC2(12

VCC1 (5

MB3773

Logic circuit

1

8

RESET

2

7

RESET

CT

3

6

4

5

30 kΩ

R3

180 kΩ

R4

+

10 kΩ

R6

CK

NMI or port

GND

+

_

1.2 kΩ

R1

Comp. 1

_

Comp. 2

5.1 kΩ

R2

4.7 kΩ

R5

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 drops, Comp. 2 interrupts the logic circuit.

• Use VCC1 (  5 V) to power the comparators (Comp. 1 and Comp. 2) in the external circuit shown above.

• The detection voltage of the VCC2 (  12 V) supply voltage is approximately 9.2 V/9.4 V and has a hysteresis width

of approximately 0.2 V.

VCC2 detection voltage and hysteresis width can be found using the following formulas:

→ Detection voltage

V2H



R3  (R4 // R5)

R4 // R5

× VREF (Approximately 9.4 V in the above illustration)

V2L 

R3  R5

R5

× VREF

(Approximately 9.2 V in the above illustration)

→ Hysteresis width VHYS  V2H  V2L

Document Number: 002-08513 Rev. *A

Page 16 of 31

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