PIC24FJ256GB110-I Datasheet, PDF (278/328 Pages) Microchip Technology – 64/80/100-Pin, 16-Bit Flash Microcontrollers with USB On-The-Go (OTG)

PIC24FJ256GB110 FAMILY
25.2.3 ON-CHIP REGULATOR AND BOR
When the on-chip regulator is enabled,
PIC24FJ256GB110 family devices also have a simple
brown-out capability. If the voltage supplied to the reg-
ulator is inadequate to maintain the tracking level, the
regulator Reset circuitry will generate a Brown-out
Reset. This event is captured by the BOR flag bit
(RCON<1>). The brown-out voltage specifications are
provided in Section 7. Reset” (DS39712) in the
“PIC24F Family Reference Manual”.
25.2.4 POWER-UP REQUIREMENTS
The on-chip regulator is designed to meet the power-up
requirements for the device. If the application does not
use the regulator, then strict power-up conditions must
be adhered to. While powering up, VDDCORE must
never exceed VDD by 0.3 volts.
Note: For more information, see Section 28.0
“Electrical Characteristics”.
25.2.5 VOLTAGE REGULATOR STANDBY
MODE
When enabled, the on-chip regulator always consumes
a small incremental amount of current over IDD/IPD,
including when the device is in Sleep mode, even
though the core digital logic does not require power. To
provide additional savings in applications where power
resources are critical, the regulator automatically
disables itself whenever the device goes into Sleep
mode. This feature is controlled by the VREGS bit
(RCON<8>). By default, this bit is cleared, which
enables Standby mode. When waking up from Standby
mode, the regulator will require around 190 μs to
wake-up. This extra time is needed to ensure that the
regulator can source enough current to power the
Flash memory.
For applications which require a faster wake-up time, it
is possible to disable regulator Standby mode. The
VREGS bit (RCON<8>) can be set to turn off Standby
mode so that the Flash stays powered when in Sleep
mode and the device can wake-up in 10 μs. When
VREGS is set, the power consumption while in Sleep
mode, will be approximately 40 μA higher than power
consumption when the regulator is allowed to enter
Standby mode.
25.3 Watchdog Timer (WDT)
For PIC24FJ256GB110 family devices, the WDT is
driven by the LPRC oscillator. When the WDT is
enabled, the clock source is also enabled.
The nominal WDT clock source from LPRC is 31 kHz.
This feeds a prescaler that can be configured for either
5-bit (divide-by-32) or 7-bit (divide-by-128) operation.
The prescaler is set by the FWPSA Configuration bit.
With a 31 kHz input, the prescaler yields a nominal
WDT time-out period (TWDT) of 1 ms in 5-bit mode, or
4 ms in 7-bit mode.
A variable postscaler divides down the WDT prescaler
output and allows for a wide range of time-out periods.
The postscaler is controlled by the WDTPS3:WDTPS0
Configuration bits (CW1<3:0>), which allow the selec-
tion of a total of 16 settings, from 1:1 to 1:32,768. Using
the prescaler and postscaler, time-out periods ranging
from 1 ms to 131 seconds can be achieved.
The WDT, prescaler and postscaler are reset:
• On any device Reset
• On the completion of a clock switch, whether
invoked by software (i.e., setting the OSWEN bit
after changing the NOSC bits), or by hardware
(i.e., Fail-Safe Clock Monitor)
• When a PWRSAV instruction is executed
(i.e., Sleep or Idle mode is entered)
• When the device exits Sleep or Idle mode to
resume normal operation
• By a CLRWDT instruction during normal execution
If the WDT is enabled, it will continue to run during
Sleep or Idle modes. When the WDT time-out occurs,
the device will wake the device and code execution will
continue from where the PWRSAV instruction was exe-
cuted. The corresponding SLEEP or IDLE bits
(RCON<3:2>) will need to be cleared in software after
the device wakes up.
The WDT Flag bit, WDTO (RCON<4>), is not auto-
matically cleared following a WDT time-out. To detect
subsequent WDT events, the flag must be cleared in
software.
Note:
The CLRWDT and PWRSAV instructions
clear the prescaler and postscaler counts
when executed.
DS39897B-page 276
Preliminary
© 2008 Microchip Technology Inc.