TC51 datasheet(5/14 Pages) MICROCHIP

5 / 14 page

 2002 Microchip Technology Inc.

DS21429B-page 5

TC51

4.0

APPLICATIONS INFORMATION

4.1

Processor RESET Supervisor

Figure 4-1 shows the TC51 used as a processor reset

supervisor. Because the TC51 is available in threshold

settings of 1.6V to 6.0V, the user can choose the reset

single threshold setting best suited to the system power

supply voltage at hand. Also, the 1

µA supply current is

significantly lower than its nearest competitor.

As shown in the timing diagram (Figure 3-1),VOUT is

low for voltages between 0.7V and VDET+. The TC51

activates its on-board delay timer once the power

supply voltage is within tolerance (i.e., greater than

VDET+). VOUT is released after delay time (TDLY).

Should the power supply voltage momentarily dip

(“brown-out” condition), the TC51 immediately drives

and holds the processor RESET input low. RESET is

released after the power supply voltage is again within

tolerance, and after the delay timer expires. RESET is

driven and held low when power fails (power-off or

“blackout”), and is maintained down low to a supply

voltage of 0.7V.

FIGURE 4-1:

PROCESSOR RESET

SUPERVISOR

FIGURE 4-2:

TC51 OPERATION DURING POWER-UP, BROWN-OUT AND POWER DOWN

TC51

VOUT

GND

VDD

Processor

RESET

47K

0.7V

Power-Up

Steady

State

Operation

TDLY

Time

TDLY

Brown-Out

Power Down

Nominal

Power Supply

Voltage

Threshold

Voltage

(VDET-, VDET+)

VOH

TC51 Output

VOL

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