TC1270AMCVRCTR datasheet(18/40 Pages) MICROCHIP

18 / 40 page

TC1270A/70AN/71A

DS22035B-page 18

FIGURE 4-4:

TC1270A Block Diagram.

FIGURE 4-5:

TC1270AN Block Diagram.

FIGURE 4-6:

TC1271A Block Diagram.

4.2

Voltage Detect Circuit

The Voltage Detect Circuit monitors VDD. The device’s

Reset voltage trip point (VTRIP) is selected when the

device is ordered. The voltage on the device’s VDD pin

determines the output state of the RST/RST pin.

VDD voltages above the VTRIP(MAX) force the RST/RST

pin inactive. VDD voltages below the VTRIP(MIN) force

the RST/RST pin active. The state of the RST/RST pin

is unknown for VDD voltages between VTRIP(MAX) and

VTRIP(MIN). This is shown in Table 4-1

TABLE 4-1:

VDD LEVELS TO RST/RST

OUTPUT STATES

The term VTRIP will be used as the general term for the

trip point voltage where the device actually trips.

In the case where VDD is falling (for voltages starting

above VTRIP(MAX)):

• Voltages above VTRIP(MAX) will never cause the

RST/RST output pin to be driven Active.

• Voltages below VTRIP(MIN) will always cause the

RST/RST output pin to be driven Active.

Now in the case where VDD is rising (for voltages

starting below VTRIP(MIN)):

• Voltages above VTRIP(MAX) will always cause the

RST/RST output pin to be driven Inactive, (or

floated - TC1270AN) after the Reset Delay Timer

(tRST), times out.

VDD

Comparator

–

Output

Driver

RST

Reference

Noise Filter

Voltage

Delay

(Push-

Pull)

VDD

Comparator

–

RST

Reference

VSS

Noise Filter

Voltage

Delay

Output

Driver

(Open-

Drain)

VDD

Comparator

–

RST

Reference

Noise Filter

Voltage

Delay

Output

Driver

(Push-

Pull)

VDD Voltage Level

Output State

RST

VDD ≥ VTRIP(MAX)

H (1, 2)

L (1)

VTRIP(MIN) < VDD < VTRIP(MAX)

VDD ≤ VTRIP(MIN)

Legend: H = Driven High

L = Driven Low

U = Unknown, driven either High or Low

Note 1:

The RST/RST pin will be driven inactive

after the Reset Delay Timer (tRST) times

out.

The TC1270AN RST pin will be floated

after the Reset Delay Timer (tRST) times

out.

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