Table of Contents
Advertisement
• Programmable voltage reference
• USB full-speed/low-speed OTG/Host/Device controller with device charge detect
2
• SPI, I
C (w/ SMBUS support), UART (w/ ISO7816 and IrDA), CAN, I
• GPIO with pin interrupt support, DMA request capability, digital glitch filtering
• Capacitive touch sensing inputs (TSI)
• Debug interfaces: JTAG, cJTAG, SWD
• Trace: TPIO, FPB, DWT, ITM
2.2 Clocking
The Kinetis MCUs start up from an internal digitally controlled oscillator (DCO). Software can enable
one or two external oscillators if desired. The external oscillator for the multipurpose clock generator
(MCG) module can range from 32.768 KHz up to a 32 MHz crystal or ceramic resonator. The external
oscillator for the real time clock (RTC) module accepts a 32.768 kHz crystal.
Two crystals are provided on board for clocking the K20D72M device: 8 MHz crystal as main oscillator
to clock MCG module and 32.768 kHz crystal for clocking RTC module.
2.3 System Power
In standalone operation, the main power source for the TWR-K20D72M is derived from the 5.0V input
from either the USB mini-B connector, J14 or the debugger header, J11, when a shunt is placed on
jumper J10. On board low-dropout regulator provides either 3.3V or 1.8V supply from the 5.0V input
voltage based on jumper settings on J17, refer to sheet 5 of the TWR-K20D72M schematic for details.
When installed into a Tower System, the TWR-K20D72M can be powered from either an on-board
source or from another source in the assembled Tower System. If both the on-board and off-board
sources are available, the TWR-K20D72M will default to the off-board source.
The 3.3V or 1.8V power supplied to the MCU is routed through a jumper, J6. The jumper shunt can be
removed to allow for either 1) alternate MCU supply voltages to be injected or 2) the measurement of
power consumed by the MCU.
2.3.1 Board Power Select
TWR-K20D72M board include on board regulators for both 3.3V and 1.8V output and add jumper J17
to select which one to use as board power and CPU power. This allows MCU operation under 1.8V
power supply.
2.3.2 RTC VBAT
The real time clock (RTC) module on the K20D72M has two modes of operation, system power-up and
system power-down. During system power-down, the RTC is powered from the backup power supply,
VBAT. The TWR-K20D72M provides a battery holder for a coin cell battery that can be used as the
TWR-K20D72M User's Manual
2
S
Page 7 of 17
Advertisement
Table of Contents
