User Manual

12311-MRB
12311 Development Hardware Reference Manual, Rev. 1
Freescale Semiconductor 3-9
3.3.1 Power Management
The 12311-MRB power management circuit is shown in Figure 3-8.
Figure 3-8. 12311-MRB Power Management Circuit
Power to the 12311-MRB can be configured in several ways and the circuit has the following features:
• Board can be supplied through the IO headers (V_BRD)
• Board can be supplied from an external DC supply (J6)
— The external supply can be unregulated (V_UNREG) and make use of the onboard 3.3 V LDO
regulator
— The external supply voltage can be used directly without use of the LDO
• 8-Pin 2x4 header J13 provides means to supply current to various board components and also
measure current if desired
• Green LED D1 is available as a power indicator.
Table 3-2 shows the header configuration information for the various power supply modes.
NOTE
• The Freescale TWR-RF development boards generate the system power
supply on the motherboard and supply the voltage to the 12311-MRB
through the V_BRD pin of Headers J2 and J3. In this mode, the current
flows to the 12311-MRB through the pins.
• If an external supply is used via 12311-MRB header J5, current flows to
the motherboard through the V_BRD pin of Headers J2 and J3. THE
MOTHERBOARD SUPPLY SHOULD NOT BE USED.
• In all modes, the IO voltage supply of peripherals on a motherboard
must be the same voltage as V_BRD, which is also the voltage applied
to the IC MC1213x.