Freescale Semiconductor, Inc
FRDM-K20D50MUM
Page 8 of 17
FRDM-K20D50M Power Supplies
Power Supply Name
Description
P5-9V_VIN
Power supplied from the
V
IN
pin of the I/O
headers
(J9 pin 16). A Schottky diode provides
back drive protection.
P5V_SDA
Power supplied from the
OpenSDA USB
connector A Schottky diode provides back
drive protection.
P5V_K20D50M
Power supplied from the
K20D50M USB
connector A Schottky diode provides back
drive protection.
P3V3_VREG
Regulated 3.3V supply
. Sources power to the
P3V3 supply rail through a back drive
protection Schottky diode.
1
P3V3_BATT
Coin cell battery
supply voltage. Sources
power to the P3V3 supply rail through a back
drive protection Schottky diode.
P3V3
Main supply rail
for FRDM-K20D50M
assembly. May be sourced from P3V3_VREG,
P3V3_BATT, or directly from the I/O headers
(J9 pin 8)
P3V3_K20D50M
K20D50M MCU supply.
Header J4 provides a
convenient means for energy consumption
measurements.
2
P3V3_SDA
OpenSDA circuit supply.
Header J3 provides a
convenient means for energy consumption
measurements.
2
P5V_USB
Nominal
5V supplied to the I/O headers
(J9
pin 10). Sourced from either the
P5V_K20D50M or P5V_OSDA supply through
a back drive protection Schottky diode.
NOTES:
1)
By default the linear regulator, U1, is a 3.3V output regulator. However, this is a common footprint that
would allow the user to modify the assembly to utilize an alternative device such as a 1.8V or 2.5V
regulator. The K20 microcontroller has an operating range of 1.71V to 3.6V
2)
J3 and J4 are not populated by default. The two pins of these headers are shorted together by a trace on
the bottom layer of the PCB. To measure the energy consumption of either the K20 or the OpenSDA
MCU, the trace between these pins must first be cut. A current probe or a shunt resistor and voltage meter
can then be applied to measure the energy consumption on these rails.