DSPIC33FJ12MC201TESS datasheet(68/304 Pages) MICROCHIP

68 / 304 page

dsPIC33FJ12MC201/202

DS70265E-page 68

6.2

POR

A POR circuit ensures the device is reset from power-

on. The POR circuit is active until VDD crosses the

VPOR threshold and the delay TPOR has elapsed. The

delay TPOR ensures the internal device bias circuits

become stable.

The device supply voltage characteristics must meet

the

specified

starting

voltage

and

rise

rate

requirements to generate the POR. Refer to

Section 24.0 “Electrical Characteristics”

for details.

The POR status (POR) bit in the Reset Control

(RCON<0>) register is set to indicate the Power-on

Reset.

6.3

BOR and PWRT

The on-chip regulator has a BOR circuit that resets the

device when the VDD is too low (VDD < VBOR) for proper

device operation. The BOR circuit keeps the device in

Reset until VDD crosses the VBOR threshold and the

delay TBOR has elapsed. The delay TBOR ensures the

voltage regulator output becomes stable.

The BOR status (BOR) bit in the Reset Control

(RCON<1>) register is set to indicate the Brown-out

Reset.

The device will not run at full speed after a BOR as the

VDD should rise to acceptable levels for full-speed

operation. The PWRT provides power-up time delay

(TPWRT) to ensure that the system power supplies have

stabilized at the appropriate levels for full-speed

operation before the SYSRST is released.

The power-up timer delay (TPWRT) is programmed by

the

Power-on

Reset

Timer

Value

Select

(FPWRT<2:0>) bits in the POR Configuration

(FPOR<2:0>) register, which provides eight settings

(from 0 ms to 128 ms). Refer to Section 21.0 “Special

Features”

for further details.

Figure 6-3 shows the typical brown-out scenarios. The

Reset delay (TBOR + TPWRT) is initiated each time VDD

rises above the VBOR trip point.

FIGURE 6-3:

BROWN-OUT SITUATIONS

VDD

SYSRST

VBOR

VDD

SYSRST

VBOR

VDD

SYSRST

VBOR

TBOR + TPWRT

VDD dips before PWRT expires

TBOR + TPWRT

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