NXP Semiconductors MPC5644A, Reference Manual, Page: 1647 / 1735

Power Management Controller (PMC)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 1647
35.4 Functional description
The power management controller provides the base current for an external ballast transistor to generate
the 1.2 V supply. It also contains a 3.3 V regulator and several POR / LVI voltage monitors for system
supervision.
A 5 V loose tolerance detection circuit (POR 5 V) is used to determine if the supply voltage VDDREG is
high enough to guarantee the startup of bandgap voltage reference. As a consequence 5 V and 3 V LVIs
can safely startup with reliable output value. The device is kept in reset until 5 V LVI has been cleared,
allowing for correct 3.3 V regulator, 1.2 V regulator and 1.2 V LVI startup. Internal 3.3 V and 1.2 V POR
are included to provide minimum low voltage reset capability.
Internal 3.3 V and 1.2 V POR are included to provide minimum low voltage reset capability.
The voltage regulators can be disabled to support the connection of external power supplies to the 3.3 V
and 1.2 V pins. It can be done in two ways:
1. Grounding VDDREG
Internal regulators are automatically disabled, external bipolar transistor is omitted. In this case, all
LVI monitors are also disabled. Therefore, when using external power supplies and grounding
VDDREG, the user has to provide external LVI monitoring.
2. Keeping VDDREG powered
External bipolar transistor is omitted, 3.3 V internal regulator is disabled after startup by setting the
V33DIS bit in the NVUSRO register (Non Volatile User Option register in the flash memory. See
Section 35.4.3, 3.3 V internal voltage regulator for more details.). In this case there is no need of
external LVI monitoring.
As PORs are powered by VHH their value is reliable also when VDDREG is grounded, as long as
VDDEH1 or VDD33 are at the correct voltage.
35.4.1 Bandgap
The bandgap voltage of the PMC is capable of generating a reference voltage of 1.219 V. It is used as
reference to generate all supply voltages, for this reason it is powered directly out of the 5 V domain to
avoid startup racing conditions. Supply voltage range is from 4.5 V to 5.5 V. The bandgap shall work with
decreased performance down to 4.0 V supply.
The bandgap is calibrated during factory test—see the “PMC Electrical Characteristics” table in the device
data sheet for accuracy details. The calibration data is typically stored in flash memory and is automatically
read from the flash every time the part is initiated through reset. The default LVI thresholds are set to a
safe value that accommodates the full uncalibrated bandgap range, so that external voltages can be applied
in the specified ranges—see the “PMC Electrical Characteristics” table in the device data sheet for details.
The bandgap has two monitor signals: bandgap_OK and temperature_OK. The former is low during
startup and rises when bandgap reference has settled (uses an internal POR on the bandgap supply); the
latter is a low accuracy temperature sensor, which goes low when an over temperature condition has
occurred, i.e., when local temperature is higher than 160 – 200 °C. Both signals and POR value are
available in the status register (PMC_SR) as bandgap status bits.