NXP Semiconductors MPC5746R - Operating Conditions

MPC5746R Hardware Design Guide, Rev. 1
Power Supply
NXP Semiconductors8
3.2 On-chip 1.25 V Regulator
In order to lower system cost, MPC5746R provides an on-chip regulator that can use an external NPN pass
transistor to provide the 1.25 V core supply voltage from either a 5.0 V or 3.3 V supply. The recommended
external circuits are shown in Figure 4.
Figure 4. 1.25 V Supply with external pass Transistor
When the 5.0 V supply configuration is in use, the internal regulator regulates the BJT emitter voltage to
1.25[V], which is used as the core supply (
VDD_LV). The remaining energy needs to be dissipated via the
transistor as heat. The capability of the transistor package to dissipate heat degrades as the temperature
increases. To overcome such problems, the user should analyze the thermal capabilities of the transistor and
add sufficient heat dissipation options as needed.
VDD_HV_FLA
4
3.3 V 1 μF~2.2 μF 1 nF
VDD_LV_BD
5
1.25 V 4.7 μF 100 nF
VDD_HV_IO_BD
5
5.0 V 4.7 μF 100 nF
VDDSTBY 1.3 V–5.9 V 1 μF 100 nF
1
This supply may be optionally provided by the on-chip regulator using a bipolar junction transistor (BJT). See Section 3.1.2.
2
Recommend 4 x 4.7 uF bulk capacitors with lower ESR (each < 200 mΩ) for VDD_LV supply domain.
3
Recommend 5 x 4.7 uF bulk capacitors for VDD_HV_IO_MAIN supply domain.
4
No connection to external supply required.
5
Only present on the 292 MAPBGA emulation device.
Table 6. Supply Decoupling Requirements
Domain Supply Voltage Bulk Bypass (each pin)