MB3771 datasheet(9/24 Pages) CYPRESS

9 / 24 page

MB3771

Document Number: 002-08511 Rev. *A

Page 9 of 24

8.3 Arbitrary Voltage Supply Monitor

8.3.1 Case: VCC

 18 V

■ Detection Voltage can be set by R1 and R2.

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

■ Connect Pin 7 to VCC when VCC less than 4.45 V.

■ Pin 7 can be opened when VCC greater than 4.45 V

Power Dissipation can be reduced.

Note: Hysteresis of 28 mV at VSB at termination is available.

Hysteresis width dose not depend on (R1 + R2).........

8.3.2 Monitoring VCC > 18 V

■ Detection Voltage can be set by R1 and R2

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

■ The RESET signal output is := 0V (low level) and := 5 V (high level). VCC voltage cannot be output.

Do not pull up RESET to VCC.

■ Changing the resistance ratio between R4 and R5 changes the constant voltage output, thereby changing the voltage of the

high level RESET output. Note that the constant voltage output should not exceed 18 V.

■ The 5 V output can be used as a power supply for control circuits with low current consumption.

■ In setting the R3 resistance level, caution should be given to the power consumption in the resistor. The table below lists

sample resistance values for reference (using 1/4

 resistance).

■ Values are actual measured values (using IOUTC = 100 A, VOLC = 0.4 V). Lowering the resistance value of R3 reduces the

minimum supply voltage of the RESET output, but requires resistance with higher allowable loss.

VCC (V)

Detection

voltage (V)

RESET Output min. power

supply voltage (V)

R1 (MΩ)

R2 (kΩ)

R3 (kΩ)

Output Current

(mA)

140

100

6.7

1.6

110

< 0.2

100

3.8

1.3

< 0.5

1.4

0.51

< 1.6

VCC

RESET

MB3771

VCC

RESET

33 k

0.47

μF

100 k

5 V output(Stablized)

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