Kinetis® K21-50 MHz, Full-Speed USB, Anti-Tamper Microcontrollers based on Arm® Cortex®-M4 Core

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Block Diagram

Kinetis K21_50 MCUs Block Diagram

Kinetis K21_50 MCUs Block Diagram



  • 11 low-power modes with power and clock gating for optimal peripheral activity and recovery times. 4 µs wake-up from Stop mode
  • Full memory and analog operation down to 1.71 volts for extended battery life
  • Low-leakage wake-up unit with up to eight internal modules and 16 pins as wake-up sources in low-leakage stop (LLS)/very low-leakage stop (VLLS) modes
  • Low-power timer for continual system operation in reduced power state

Flash, SRAM and FlexMemory

  • 128 KB-512 KB flash. Fast access, high reliability with 4-level security protection
  • Up to 64 KB FlexRAM
    • FlexMemory
    • Up to 4 KB of user-segmentable byte write/erase EEPROM for data tables/system data
    • EEPROM with over 10M cycles and flash with 100 µsec write time (brownouts without data loss or corruption)
    • No user or system intervention to complete programming and erase functions and full operation down to 1.71 volts
    • In addition, FlexNVM from 64 KB for extra program code, data or EEPROM backup


  • 50 MHz Arm® Cortex®-M4 core with DSP instruction set, single cycle MAC and single instruction multiple data (SIMD) extensions.
  • Up to 16-channel DMA for peripheral and memory servicing with reduced CPU loading and faster system through put 0 MHz core
  • Cross bar switch enables concurrent multi-leader bus accesses, increasing bus bandwidth

Timing and Control

  • Up to two FlexTimers with a total of 10 channels. Hardware dead-time insertion and quadrature decoding for motor control
  • Carrier modulator timer for infrared waveform generation in remote control applications
  • Four-channel 32-bit periodic interrupt timer provides time base for RTOS task scheduler or trigger source for ADC conversion and programmable delay block

Connectivity and Communications

  • Up to three UARTs. One UART supports RS232 with flow control, RS485, ISO7816 and IrDA. All other two UARTS support RS232 with flow control and RS485
  • One inter-IC Sound (I²S) serial interface for audio system interfacing
  • One DSPI and one I²C

Reliability, Safety and Security

  • >Hardware Encryption coprocessor for secure data transfer and storage. Faster than software implementations and with minimal CPU loading. Supports a wide variety of algorithms - DES, 3DES, AES, MD5, SHA-1, SHA-256
  • System security and tamper detect with secure real-time clock with independent battery supply. Secure key storage with internal/external tamper detect for unsecure flash, temperature, clock, and supply voltage variations and physical attack detection
  • Cyclic redundancy check engine validates memory contents and communication data, increasing system reliability
  • Independent-clocked COP guards against clock skew or code runaway for fail-safe applications such as the IEC 60730 safety standard for household appliances
  • External watchdog monitor drives output pin to safe state external components if watchdog event occurs

Part numbers include: MK21DN512AVLK5, MK21DN512AVMC5, MK21DX128AVLK5, MK21DX128AVMC5, MK21DX256AVLK5, MK21DX256AVMC5.


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Design Files

Quick reference to our design files types.

2 design files

  • Symbols and Footprints

    Kinetis® Symbols, Footprints and Models

  • Calculators

    TFS FlexMem Endurance Calculator


Quick reference to our board types.

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Note: For better experience, software downloads are recommended on desktop.

Engineering Services

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To find additional partner offerings that support this product, visit our Partner Marketplace.


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