MB3771 datasheet(10/24 Pages) CYPRESS

10 / 24 page

MB3771

Document Number: 002-08511 Rev. *A

Page 10 of 24

8.4 5 V and 12 V Power Supply Monitor (2 types of power supply monitor VCC1 = 5 V, VCC2 =12 V)

■ 5 V is monitored by VSA. Detection voltage is about 4.2 V

■ 12 V is monitored by VSB. When R1 = 390 k and R2 = 62 k, Detection voltage is about 9.0 V.Generally the detection voltage is

determined by the following equation.

Detection Voltage = (R1 + R2)  VSB/R2

8.5 5 V and 12 V Power Supply Monitor (RESET signal is generated by 5 V, VCC1 = 5 V, VCC2 = 12 V)

■ 5 V is monitored by VSA, and generates RESET signal when VSA detects voltage sagging.

■ 12 V is monitored by VSC, and generates its detection signal at OUTC.

■ The detection voltage of 12 V monitoring and its hysteresis is determined by the following equations.

Detection voltage =

R1 + R2 + R3  V

(8.95 V in the circuit above)

R2 + R3

Hysteresis width =

R1 (R3  R3 // R4)

 VSC

(200 mV in the circuit above)

(R2 + R3) (R2 + R3 // R4)

VCC2

MB3771

R1: 390 k

R2: 62 k

RESET

VCC1

Logic

circuit

VCC2

MB3771

R1: 390 k

R2: 33 k

RESET

VCC1

IRQ

R L: 10 k

R5: 100 k

R3: 30 k

R4: 510 k

Port Logic Circuit

MB3771 Datasheet(PDF) 10 Page - Cypress Semiconductor