TC1270ASBVRCTR datasheet(20/40 Pages) MICROCHIP

20 / 40 page

TC1270A/70AN/71A

DS22035B-page 20

4.2.3

POWER-DOWN/BROWN-OUTS

As the device powers-down/brown-outs, the VDD falls

from a voltage above the devices trip point (VTRIP). The

device will trip at a voltage between the maximum trip

point

(VTRIP(MAX)) and the minimum trip point

(VTRIP(MIN)). Once the device voltage (VDD) goes

below this voltage, the RST/RST pin will be forced to

the active state.

Figure 4-8 shows the waveform of the RST pin as

determined by the VDD voltage. As the VDD voltage falls

from the normal operating point, the device “enters”

reset

crossing

the

VTRIP voltage (between

VTRIP(MAX) and VTRIP(MIN)). Then when VDD voltage

rises, the device “exits” reset by crossing the VTRIP volt-

age (below or at VTRIP(MAX)). After the “exit” state has

been detected, the Reset Delay Timer (tRST) starts.

Once the tRST time completes, the Reset pin is driven

inactive.

Table 4-3 shows the state of the RST or RST pins.

TABLE 4-3:

RESET PIN STATES

FIGURE 4-8:

RST

Operation as determined by the VTRIP.

Device

State of RST Pin when:

Output Driver

VDD < VTRIP

VDD > VTRIP

(1)

VDD < VTRIP

VDD > VTRIP

(1)

TC1270A

—

Push-Pull

TC1271A

—

Push-Pull

Note 1:

The RST/RST pin will be driven inactive after the Reset Delay Timer (tRST) times out.

VDD

VTRIP

RST(1)

< 1V is outside the

device specifications

tRD

tRST

tRD

tRST

VTRIP

(with VDD Falling)

(with VDD Rising)

Note 1:

The TC1270AN requires an external pull-up resistor.

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