XC886/888CLM
Power Supply, Reset and Clock Management
User’s Manual
7-2
V1.3, 2010-02
Power, Reset and Clock, V 1.0
EVR Features:
•
Input voltage (
V
DDP
): 3.3 V/5.0 V
•
Output voltage (
V
DDC
): 2.5 V +/-7.5%
•
Low power voltage regulator provided in power-down mode
•
V
DDC
and
V
DDP
prewarning detection
•
V
DDC
brownout detection
The EVR consists of a main voltage regulator and a low power voltage regulator. In
active mode, both voltage regulators are enabled. In power-down mode, the main
voltage regulator is switched off, while the low power voltage regulator continues to
function and provide power supply to the system with low power consumption.
The EVR has the
V
DDC
and
V
DDP
detectors. There are two threshold voltage levels for
V
DDC
detection: prewarning (2.3 V) and brownout (2.1 V). When
V
DDC
is below 2.3 V, the
V
DDC
NMI flag NMISR.FNMIVDD is set and an NMI request to the CPU is activated
provided
V
DDC
NMI is enabled (NMICON.NMIVDD). If
V
DDC
is below 2.1 V, the brownout
reset is activated, putting the microcontroller into a reset state.
For
V
DDP
, there is only one prewarning threshold of 4.0 V if the external power supply is
5.0 V. When
V
DDP
is below 4.0 V, the
V
DDP
NMI flag NMISR.FNMIVDDP is set and an
NMI request to the CPU is activated provided
V
DDP
NMI is enabled
(NMICON.NMIVDDP).
If an external power supply of 3.3 V is used, the user must disable
V
DDP
detector by
clearing bit NMICON.NMIVDDP. In power-down mode, the
V
DDC
detector is switched off
while
V
DDP
detector continues to function.
The EVR also has a power-on reset (POR) detector for
V
DDC
to ensure correct power up.
The voltage level detection of POR is 1.5 V. The monitoring function is used in both
active mode and power-down mode. During power up, after
V
DDC
exceeds 1.5 V, the
reset of EVR is extended by a delay that is typically 300
µ
s. In active mode,
V
DDC
is
monitored mainly by the
V
DDC
detector, and a reset is generated when
V
DDC
drops below
2.1 V. In power-down mode, the
V
DDC
is monitored by the POR and a reset is generated
when
V
DDC
drops below 1.5 V.
*
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