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Ambiq Rides Quadratic Power Curve

January 24, 2017

Author: Loyd Case

Ambiq Micro’s new Apollo 2 processor uses a 48MHz Cortex-M4F CPU that consumes less than 10 microamps per megahertz when executing from flash memory or embedded SRAM. Mainstream MCUs that sport the same ARM CPU require 80 microamps per megahertz or more. Ambiq reaches its bold power goals by running much of the SoC at subthreshold voltages. Subthreshold circuits drive transistors at voltages less than what’s necessary to create a conducting path between the source and drain. Although it employs standard supply voltages, Ambiq has tuned portions of both the logic and analog circuitry to run at about 0.5V internally. This voltage reduction extends battery life for IoT and wearable devices. The new MCU first sampled in 2Q16 and is scheduled to begin production in 1H17.

Ambiq developed a proprietary ultra-low-voltage approach called Subthreshold Power Optimized Technology (SPOT), which it used in several products before Apollo 2. Among those products are a pair of RTCs (one of which incorporates a PMIC) and the original Apollo MCU, which employs a 24MHz Cortex-M4F CPU.

The company implemented the logic (including the CPU’s physical layout), analog components, and memory using subthreshold circuits. Running at these extremely low voltages greatly reduces power consumption, which decreases quadratically with voltage. Similar microcontrollers from NXP and STMicroelectronics require 10–30x more operational current.

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