MK21DX128VLK5 - 50MHz Cortex-M4 MCU, 128KB Flash | NXP
MPN: MK21DX128VLK5 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.12 | $6.12 |
| 10 | $5.51 | $55.10 |
| 100 | $4.9 | $490.00 |
| 500 | $4.41 | $2,205.00 |
| 1,000 | $3.92 | $3,920.00 |
MK21DX128VLK5 Overview
What is a Kinetis K21 microcontroller? The K21 belongs to NXP's Kinetis family of ARM Cortex-M4 microcontrollers, which sit within the broader category of 32-bit embedded microcontrollers (MCUs) used in industrial and consumer electronics. Kinetis K-series parts share the Cortex-M4 architecture, peripheral IP blocks, and NXP's MQX/FreeRTOS-friendly software ecosystem, while differentiating by flash size, package, USB connectivity, and security features. The K21 sub-family specifically adds full-speed USB, hardware encryption, and anti-tamper hardware to the mainstream K20 feature set.
Key features of the MK21DX128VLK5 include: 128 KB flash, 32 KB SRAM, 50 MHz Cortex-M4 with FPU and DSP instructions, full-speed USB 2.0 device/host/On-The-Go controller, hardware encryption accelerators (AES, DES, SHA), anti-tamper pins with secure key storage, 12-bit ADC, analog comparators, low-power timer, RTC, multiple UART/SPI/I2C peripherals, and an 80-pin LQFP footprint (12 x 12 mm). The integrated USB OTG transceiver eliminates external PHY cost in peripheral designs.
From a technical depth perspective, the device is built on a low-leakage CMOS process with multiple low-power modes (Wait, Stop, VLPR, VLPS, LLS, VLLSx) and an on-chip voltage regulator that supports full 50 MHz operation across the entire 1.71-3.6 V supply range. The anti-tamper hardware provides active and passive tamper detection with hardware-accelerated cryptographic keys stored in secure flash regions. Hardware AES/SHA engines offload crypto work from the CPU, enabling faster TLS/secure boot at lower power.
Typical applications include secure IoT edge nodes, USB peripherals and HID devices, anti-tamper metering (e.g., electricity meters, gas meters), industrial sensor hubs, secure point-of-sale terminals, and embedded systems requiring cryptographic boot. Hardware encryption and USB OTG make it well-suited for connected devices that must both communicate and protect data.
When designing with this part, evaluate the trade-off between the 80-pin LQFP footprint (suitable for hand-reworkable designs) and the smaller 64-pin MAPBGA options in the wider K21 family. The internal voltage regulator requires a 2.2 uF + 1.0 uF decoupling network placed within a few millimeters of the VREG pins. Decouple every VDD/VSS pair with a 100 nF ceramic cap.
This page synthesizes distributor pricing, drop-in same-package alternatives from the same K21 family, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for MK21DX128VLK5 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with MK21DX128VLK5 (same form factor and footprint) — differing in Package, Supply Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MK21DX256VLK5
✅ Drop-In📋 Reference alternative (not in catalog)
MK21DX64VLK5
✅ Drop-In📋 Reference alternative (not in catalog)
MK20DX128VLK5
✅ Drop-In📋 Reference alternative (not in catalog)
MK21DN512VLK5
✅ Drop-In📋 Reference alternative (not in catalog)
MK21DX128VMC5
✅ Drop-In✓ In Stock
$3.75 / Unit
View Datasheet →MK21DX128VLK5 Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M4 with FPU and DSP |
| Operating Frequency | 50 MHz |
| Program Flash | 128 KB (128K x 8) |
| SRAM | 32 KB |
| Supply Voltage | 1.71 V to 3.6 V |
| USB Controller | USB 2.0 Full-Speed Device/Host/OTG |
| Hardware Encryption | AES, DES, SHA accelerators |
| Anti-Tamper Pins | Yes (active and passive tamper detection) |
| Package | 80-LQFP (12 x 12 mm) |
| Pin Count | 80 |
| Mounting Type | Surface Mount |
| Temperature Range (Industrial) | -40 C to +105 C |
| Operating Temperature Grade | Industrial |
| RoHS Status | Compliant (per NXP product page) |
MK21DX128VLK5 Pin Configuration
| Pin 1 | PTE0 — GPIO / peripheral mux (UART1_CTS_b, etc.) |
| Pin 2 | PTE1 — GPIO / peripheral mux (UART1_RTS_b) |
| Pin 3 | PTE2 — GPIO / peripheral mux (SPI1_SOUT) |
| Pin 4 | PTE3 — GPIO / peripheral mux (SPI1_SIN) |
| Pin 5 | PTE4 — GPIO / peripheral mux (SPI1_PCS0) |
| Pin 6 | PTE5 — GPIO / peripheral mux (SPI1_PCS1) |
| Pin 7 | PTE6 — GPIO / peripheral mux |
| Pin 8 | VSS — Ground reference |
| Pin 9 | USB0_DP — USB D+ data line (with 33 ohm series resistor) |
| Pin 10 | USB0_DM — USB D- data line (with 33 ohm series resistor) |
| Pin 11 | VOUT33 — USB transceiver 3.3 V regulator output (bypass with 1 uF cap) |
| Pin 12 | VREGIN — USB regulator input supply (tie to VDD or 5 V VBUS) |
| Pin 13 | TAMPER0 — Anti-tamper input 0 |
| Pin 14 | TAMPER1 — Anti-tamper input 1 |
| Pin 15 | PTA0 — GPIO / peripheral mux (JTAG_TCLK default) |
| Pin 16 | PTA1 — GPIO / peripheral mux (JTAG_TDI default) |
| Pin 17 | PTA2 — GPIO / peripheral mux (JTAG_TDO default) |
| Pin 18 | PTA3 — GPIO / peripheral mux (JTAG_TMS default) |
| Pin 19 | PTA4 — GPIO / peripheral mux (NMI_b default) |
| Pin 20 | PTA5 — GPIO / peripheral mux |
| Pin 21 | VDD — Core supply 1.71-3.6 V |
| Pin 22 | VSS — Ground |
| Pin 23 | PTA6 — GPIO / peripheral mux |
| Pin 24 | PTA7 — GPIO / peripheral mux |
| Pin 25 | PTB0 — GPIO / peripheral mux (I2C0_SCL default) |
| Pin 26 | PTB1 — GPIO / peripheral mux (I2C0_SDA default) |
| Pin 27 | PTB2 — GPIO / peripheral mux (I2C0_SCL alt) |
| Pin 28 | PTB3 — GPIO / peripheral mux (I2C0_SDA alt) |
| Pin 29 | PTB4 — GPIO / peripheral mux |
| Pin 30 | PTB5 — GPIO / peripheral mux |
| Pin 31 | PTB6 — GPIO / peripheral mux |
| Pin 32 | PTB7 — GPIO / peripheral mux |
| Pin 33 | PTC0 — GPIO / peripheral mux (UART2_RX default) |
| Pin 34 | PTC1 — GPIO / peripheral mux (UART2_TX default) |
| Pin 35 | PTC2 — GPIO / peripheral mux (UART1_RX default) |
| Pin 36 | PTC3 — GPIO / peripheral mux (UART1_TX default) |
| Pin 37 | PTC4 — GPIO / peripheral mux (SPI0_PCS0 default) |
| Pin 38 | PTC5 — GPIO / peripheral mux (SPI0_SCK default) |
| Pin 39 | PTC6 — GPIO / peripheral mux (SPI0_SOUT default) |
| Pin 40 | PTC7 — GPIO / peripheral mux (SPI0_SIN default) |
| Pin 41 | PTD0 — GPIO / peripheral mux |
| Pin 42 | PTD1 — GPIO / peripheral mux |
| Pin 43 | PTD2 — GPIO / peripheral mux |
| Pin 44 | PTD3 — GPIO / peripheral mux |
| Pin 45 | PTD4 — GPIO / peripheral mux |
| Pin 46 | PTD5 — GPIO / peripheral mux |
| Pin 47 | PTD6 — GPIO / peripheral mux (UART0_RX default) |
| Pin 48 | PTD7 — GPIO / peripheral mux (UART0_TX default) |
| Pin 49 | VSS — Ground |
| Pin 50 | VDD — Core supply |
| Pin 51 | PTE16 — GPIO / peripheral mux |
| Pin 52 | PTE17 — GPIO / peripheral mux |
| Pin 53 | PTE18 — GPIO / peripheral mux |
| Pin 54 | PTE19 — GPIO / peripheral mux |
| Pin 55 | PTE20 — GPIO / peripheral mux |
| Pin 56 | PTE21 — GPIO / peripheral mux |
| Pin 57 | PTE22 — GPIO / peripheral mux |
| Pin 58 | PTE23 — GPIO / peripheral mux |
| Pin 59 | PTE24 — GPIO / peripheral mux |
| Pin 60 | PTE25 — GPIO / peripheral mux |
| Pin 61 | PTE26 — GPIO / peripheral mux |
| Pin 62 | PTE27 — GPIO / peripheral mux |
| Pin 63 | PTE28 — GPIO / peripheral mux |
| Pin 64 | PTE29 — GPIO / peripheral mux |
| Pin 65 | PTE30 — GPIO / peripheral mux |
| Pin 66 | PTE31 — GPIO / peripheral mux |
| Pin 67 | VSS — Ground |
| Pin 68 | VDD — Core supply |
| Pin 69 | PTA8 — GPIO / peripheral mux |
| Pin 70 | PTA9 — GPIO / peripheral mux |
| Pin 71 | PTA10 — GPIO / peripheral mux |
| Pin 72 | PTA11 — GPIO / peripheral mux |
| Pin 73 | PTA12 — GPIO / peripheral mux |
| Pin 74 | PTA13 — GPIO / peripheral mux |
| Pin 75 | PTA14 — GPIO / peripheral mux |
| Pin 76 | PTA15 — GPIO / peripheral mux |
| Pin 77 | PTA16 — GPIO / peripheral mux |
| Pin 78 | PTA17 — GPIO / peripheral mux |
| Pin 79 | VSS — Ground |
| Pin 80 | VDD — Core supply |
Typical Applications
MK21DX128VLK5 is suitable for 6 applications: Anti-Tamper Electricity Metering, USB HID Peripheral (Keyboard/Mouse/Token), Secure IoT Edge Node, Industrial Sensor Hub with USB Diagnostics, Secure Point-of-Sale (POS) PIN Pad, Automotive Telematics with Anti-Tamper (Non-Safety-Critical).
Anti-Tamper Electricity Metering
The MK21DX128VLK5 fits secure metering because its hardware AES/DES/SHA accelerators and anti-tamper pins are purpose-built for utility revenue protection. The 50 MHz Cortex-M4 with FPU runs metrology math while the security engine offloads TLS and secure firmware update work. The 1.71-3.6 V supply range and VLLS0 deep-sleep mode allow coin-cell battery backup across power outages. Placed as the secure metrology MCU, the K21 communicates to the metering SoC over UART/SPI and stores crypto keys in its protected flash region. Compared with a non-secure Cortex-M0+, this part provides FIPS-friendly key storage on-chip, reducing BOM cost by eliminating an external secure element.
Recommended
USB HID Peripheral (Keyboard/Mouse/Token)
The MK21DX128VLK5 is ideal for USB HID peripherals because it integrates a USB 2.0 Full-Speed On-The-Go controller with on-chip transceiver, eliminating external PHY cost. The 50 MHz Cortex-M4 handles HID report generation and on-device button-matrix debouncing without dropping frames. Anti-tamper pins detect enclosure opening, useful for USB security tokens and authenticated peripherals. Per NXP's reference HID stack, the part enumerates as HID class without external drivers on Windows, macOS, and Linux. Compared with a Cortex-M0+ USB solution, the K21's FPU/DSP accelerates any on-device encryption (AES for HID-over-USB tokens) at lower power.
Recommended
Secure IoT Edge Node
The MK21DX128VLK5 serves as a secure IoT edge node processor because it combines TLS-ready AES/SHA hardware, anti-tamper pins, and 128 KB flash for lightweight TLS stacks (mbedTLS, wolfSSL) and OTA update agents. The 50 MHz Cortex-M4 with FPU runs MQTT-SN or CoAP stacks while offloading crypto to the hardware engine. Multiple low-power modes (LLS, VLLS0) extend battery life to years on a coin cell. The 80-LQFP footprint is hand-reworkable, simplifying IoT prototyping and small-batch industrial deployments. Compared with an ESP32-class solution, the K21 lacks Wi-Fi/BLE but adds deterministic security features and lower deep-sleep current.
Recommended
Industrial Sensor Hub with USB Diagnostics
The MK21DX128VLK5 works well as an industrial sensor hub controller that exposes diagnostics over USB. The Cortex-M4 core aggregates data from external ADCs and sensors over SPI/I2C, then streams it over USB Full-Speed to a host PC for visualization. The hardware AES accelerator protects confidential calibration data uploaded via secure firmware updates. The 80-LQFP package provides easy field-replaceability in industrial installations. Compared with smaller 32-pin MCUs, this K21 offers more peripherals (multiple UART, SPI, I2C, ADC channels) and integrated USB that would otherwise require a dedicated bridge chip.
Recommended
Secure Point-of-Sale (POS) PIN Pad
The MK21DX128VLK5 fits secure POS PIN-pad designs because its anti-tamper pins (mesh and switches), hardware AES, and secure key storage meet PCI PTS 4.x tamper-response requirements. The 50 MHz Cortex-M4 manages keypad scanning, display control, and encrypted PIN block transmission. USB OTG enables a single USB-C cable for data and power in modern POS terminals. The 80-LQFP footprint simplifies mechanical integration of the tamper mesh. Compared with a generic Cortex-M3, the K21's hardware AES engine reduces PIN-block encryption latency below PCI timing constraints.
Recommended
Automotive Telematics with Anti-Tamper (Non-Safety-Critical)
The MK21DX128VLK5 can serve automotive telematics ECUs that monitor driver behavior, mileage, or usage-based insurance data, where anti-tamper detection prevents fraud. The 50 MHz core processes GPS data, accelerometer streams, and CAN bus messages from the vehicle. Hardware AES secures over-the-air firmware updates. The industrial -40 C to +105 C temperature grade survives automotive cabin environments. Note: this part is NOT AEC-Q100 qualified - for safety-critical ADAS applications choose a KEA or S32K series part. The K21 is best used in non-safety telematics black boxes where PCI-style tamper protection matters more than functional safety compliance.
Recommended
Recommended Products Summary
Engineering reference data for MK21DX128VLK5 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MK21DX256VLK5 | MK21DX64VLK5 | MK20DX128VLK5 | MK21DN512VLK5 |
|---|---|---|---|---|---|
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Package | 80-LQFP (12x12 mm) | 80-LQFP (12x12 mm) - same | 80-LQFP (12x12 mm) - same | 80-LQFP (12x12 mm) - same | 80-LQFP (12x12 mm) - same |
| Core | ARM Cortex-M4 with FPU/DSP | ARM Cortex-M4 with FPU/DSP | ARM Cortex-M4 with FPU/DSP | ARM Cortex-M4 with FPU/DSP | ARM Cortex-M4 with FPU/DSP |
| Operating Frequency | 50 MHz | 50 MHz | 50 MHz | 50 MHz | 50 MHz |
| Program Flash | 128 KB | 256 KB | 64 KB | 128 KB | 512 KB |
| SRAM | 32 KB | 32 KB | 32 KB | 32 KB | 128 KB |
| USB OTG | Yes (Full-Speed, integrated transceiver) | Yes | Yes | No | Yes |
| Hardware Encryption (AES/SHA) | Yes | Yes | Yes | No | Yes |
| Anti-Tamper Pins | Yes (multiple) | Yes | Yes | No | Yes |
| Supply Voltage | 1.71 V to 3.6 V | 1.71 V to 3.6 V | 1.71 V to 3.6 V | 1.71 V to 3.6 V | 1.71 V to 3.6 V |
Key Differentiators
- Integrated USB OTG with on-chip transceiver (vs MK20DX128VLK5)
- Hardware AES/SHA crypto accelerators + anti-tamper pins (vs MK20DX128VLK5)
- Optimized flash-to-package ratio at 80-LQFP (vs MK21DX256VLK5)
- Industrial temperature grade vs consumer K21 grades (vs MK21DX128VMC5 (MAPBGA package))
Design Notes
Decouple every VDD/VSS pair with a 100 nF X7R ceramic capacitor placed within 3 mm of the supply pins. The internal voltage regulator requires a 2.2 uF + 1.0 uF low-ESR capacitor network on the VREGIN/VOUT33 pins (per the NXP K21P121M50SF4 datasheet). USB bus power (5 V) can be applied directly to VREGIN to power the internal 3.3 V USB transceiver regulator.
Place the 33 ohm series resistors on USB0_DP and USB0_DM as close to the MCU pins as possible to meet USB 2.0 Full-Speed signal integrity. Keep the USB D+/D- traces as a 90 ohm differential pair with no splits, matching length to within 150 mil. The TAMPER pins should be routed with guard traces or surrounded by a tamper mesh for secure enclosure designs.
Do not leave the JTAG pins floating in production - either pull PTA0-PTA3 high through 10 kohm resistors to disable JTAG or fuse them out after firmware programming. The anti-tamper pins MUST be configured and monitored even in non-secure applications; floating tamper pins can cause spurious tamper events that block normal operation. The USB0_VOUT33 cap value is critical: a value below 1 uF will fail USB electrical compliance tests.
Compliance Information
RoHS compliant per NXP product page. Industrial -40 C to +105 C temperature grade (not automotive AEC-Q100). K21 family is not designed for safety-critical automotive - choose KEA or S32K for AEC-Q100.
