pwsafe: MCU selection, first round

Werner Almesberger werner at
Wed Sep 11 18:35:58 EDT 2013

My usual criterion for sourcing components is "if Digi-Key has it,
it's safe to use" (as far as sourcing is concerned).

So I went there and did the following query:

Keyword: OTG -> 2808
Integrated Circuits (ICs) / Embedded - Microcontrollers -> 2487
In stock -> 613
Core Processor: ARM* -> 235
Voltage - Supply (min): < 2.0 V -> 183
Voltage - Supply (max): >= 3.3 V -> 152
Package / Case: <= 64 pins -> 29
Package / Case: no BGA -> 26

"-> N" indicates the number of hits remaining. At this point, all the
chips has >= 64 kB Flash and there were no T&R packagings. I sorted
by unit price for 100 units:

1.59	Freescale KL2:  MKL24Z64VFM4	M0+ 48 MHz, 32-VFQFN
2.04	Freescale KL2:  MKL25Z128VFM4	M0+ 48 MHz, 32-VFQFN
2.15	Freescale KL2:  MKL25Z128VFT4	M0+ 48 MHz, 48-VFQFN
2.21	Freescale KL2:  MKL25Z128VLH4	M0+ 48 MHz, 64-LQFP
2.55	Freescale K20:  MK20DX128VFM5	M4 50 MHz, 32-VFQFN
... more Freescale K20, KL4 ...
6.11	TI Tiva C:	TM4C1233D5PMI	M4F 80 MHz, 64-LQFP
6.67	STM32F2:	STM32F205RCT6	M3 120 MHz, 64-LQFP
7.01	TI Tiva C:	TM4C1237E6PMI	M4F 80 MHz, 64-LQFP
... more STM and TI chips in 64-LQFP ...

So this left three families: Freescale Kinetis, and there especially
the KL2 sub-series, then TI Tiva C, and finally STM32F2.

The TM4C1233D5PMI seems to have only a USB device [1], so the first
suitable TM4C in this list would be the TM4C1237E6PMI. But this isn't
correct either, and it would really be the TM4C1237D5PM, with
Digi-Key list as non-USB while TI list it as OTG.

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