[Updated: Sept. 16] — Atmel has begun sampling its most power efficient Cortex-A5 SoC yet: a Linux-ready, IoT oriented, 150mW SAMA5D2 with DDR3 and extended temperature support.

We’re somewhat surprised more semiconductor vendors haven’t tapped the Cortex-A5 design for low-power Internet of Things applications. The major exception is Atmel, which was an early supporter of Cortex-A5 SoCs in 2013 with its 536MHz SAMA5D3. Late last year, Atmel followed up with a more robust, 600MHz model called the SAMA5D4. While the more secure and multimedia friendly SAMA5D4 essentially replaced the still available SAMA5D3, the new 500MHz SAMA5D2 is offered as a low-power alternative, which Atmel claims delivers “the world’s lowest power consumption for all MPUs in its class.”

Designed for industrial IoT, wearables and POS applications, the SAMA5D2 has a lower pin-count and several ultra-small packages for space constrained applications. Like the other SAMA5D SoCs, the SAMA5D2 is a single-core solution. The SoC can clock down from 500MHz (785DMIPS) to 166MHz for ultra-low power operation. Unlike the SAMA5D4, there’s support for extended -40 to 105°C temperatures.

Block diagrams compared: SAMA5D2 (left) and SAMA5D4
(click images to enlarge)

The SoC runs at less than 150mW in active mode at 500MHz with all peripherals activated, and at less than 0.5mW in low power mode with SRAM and registers retention, claims Atmel. That’s darn good, but also apparently identical to the claims made for the SAMA5D4. Perhaps the lower consumption is found in special configurations available with Atmel’s “SleepWalking” power management technology. For example, the SAMA5D2 delivers “sub 200uA in retention mode with context preserved, 30us ultra-fast wake-up, and a new backup mode with DDR in self-refresh at only 50uA,” claims the company.

Seven variants of the SAMA5D2 are listed, with major feature differences shown as follows. Note that none of the models offer all the touted new features listed farther below, although some come close:

• SAMA5D21 — BGA196 package with 16-bit DDR
• SAMA5D22 — BGA196 package with 16-bit DDR and CAN
• SAMA5D23 — BGA196 package with 16-bit DDR, CAN, and enhanced security
• SAMA5D24 — BGA256 package with 16/32-bit DDR and USIB HSIC
• SAMA5D26 — BGA289 package with 16/32-bit DDR
• SAMA5D27 — BGA289 package with 16/32-bit DDR and CAN
• SAMA5D28 — BGA289 package with 16/32-bit DDR, CAN, and enhanced security

SAMA5D2 detailed block diagram (click to enlarge)

The SAMA5D2 debuts the SAMA5 processor family’s first DDR3 (16- or 32-bit) and USB HSIC support. There’s a 16-bit external bus interface (EBI), as well as 128KB of SRAM, a new QSPI flash interface, and ROM supported with a secure and non-secure configurable boot solution. Other features borrowed from the SAMA5D4 includes NEON and floating point support, 128KB L2 cache, which is configurable as an SRAM extension, and a pair of 32KB L1 cache allotments.

Like the SAMA5D4, but unlike the original SAM5D3, the SAMA5D2 provides robust “PCI-level” security, says Atmel. Features include TrustZone support and on-the-fly DDR3 and QSPI encryption and tamper detection. Additional security features include hardware cryptography, RSA/ECC, and memory scrambling, The device supports watchdog, temperature, voltage, and frequency monitoring, as well as unique ID tagging for each device.

Like the SAMA5D4, the SAMA5D2 provides CAN support, but overall, I/O support is somewhat more limited. For example, there’s only a single 10/100 Ethernet controller. In addition to the USB HSIC support, the SoC supports two standard USB ports, which can both be configured as host ports, or else as host and device ports.

For multimedia, you get camera and 24-bit TFT touchscreen support, as well as an audio subsystem with fractional PLL, multiple I2S and SSC/TDM channels, a stereo class D amplifier, and digital microphone support. However, the SoC lacks the SAMA5D4’s’ support for 720p video. For other I/O details, see the comparison between the SAMA5D2 and SAMA5D4 block diagrams above.

As usual, Atmel supports the SAMA5D2 with a free Linux distribution available at Linux4sam.com, which is published in the mainline kernel. More than 40 peripheral drivers in C are available for a variety of RTOSes. Atmel’s partner network is said to include IAR, ARM, Free Electrons, Active-Semi, Micron, ISSI, Winbond, Segger, Lauterbach, FreeRTOS, Express Logic, NuttX and Sequitur Labs.

 
SAMA5D2 evaluation kit

A fairly basic ATSAMA5D2-XULT (Xplained Ultra) evaluation kit is available for rapid prototyping and evaluation. The carrier board ships with an ATSAMA5D27-CU SoC, supported with 512MB of DDR3L RAM, 4GB of eMMC flash, and an option for adding QSPI flash. The 6-layer PCB carrier board also provides a Fast Ethernet port and dual USB ports.

ATSAMA5D2-XULT evaluation kit board photo and block diagram
(click images to enlarge)

The kit includes an embedded debugger and programmer, as well as “a wide range of compatible extensions boards,” says Atmel. Standalone programmer debugger solutions are also said to be available from Atmel and third parties.

 
Further information

Early samples of the SAMA5D2 are available now, and the ATSAMA5D2-XULT Xplained Ultra boards are available in October. First production quantities of the SAMA5D2 series will ship in December, starting at $4.95 in 1,000-piece quantities. The ATSAMA5D2-XULT (Xplained Ultra) kit is available for $79. More information is available at Atmel’s SAMA5D product page.