10

Shown in Figure 8 is an application using two UT01VS50D Voltage Supervisors to monitor both under voltage and over voltage of

a power supply. In this application the top Voltage Supervisor monitors the under-voltage of a 5V power supply while the bottom

Voltage Supervisor monitors the over voltage of the same 5V power supply. The 5V supply is monitored through the PFI input of

both Voltage Supervisors. Resistor values for both under voltage and over voltage monitoring can be set to accommodate a range of

power supply voltages.

During normal operation where VDD is within the allowed range (VDD_UND < VDD < VDD_OV), RESET_OD of both Voltage

Supervisors will be at logic high level. The Table 1 below shows the truth table for functional, under voltage detection and over

voltage detection.

Table 1. Under Voltage Over Voltage Truth Table

VDD

PFO_UND

PFO_OV

RESET_OD_UND

RESET_OD_OV

RESET_OD

uP or ASIC

Mode

Normal Operation

HIGH

LOW

HIGH

HIGH

HIGH

Normal

VDD < VDD_UND

LOW

LOW

LOW

HIGH

LOW

Reset Asserted

VDD > VDD_OV

HIGH

HIGH

HIGH

LOW

LOW

Reset Asserted

Figure 8. UT01VS50D Over Voltage Power Supply Monitoring and Reset

1

2 VDD

PFI

3

7

6

8

WDI

R1

R2

GND

4

5

VDD

I/O

uP

MR

1

2 VDD

PFI

3

7

6

8

WDI

R3

R4

GND

4

PFO 5

I/O

UT01VS50D

UNDER VOLTAGE

MONITOR

UT01VS50D

OVER VOLTAGE

MONITOR

VTH_UND= (R1+R2)/R2 ) * VPFI

VPFI=1.25V +/- 50mV

VTH_OV= (R3+R4)/R4 ) * VPFI

VPFI=1.25V +/- 50mV

VDD 5V

R5

R6

RESET

RESET

MR

WDO

WDO

RESET_OD

PFO

RESET_OD