Google Coral AI Taps Renesas for Programmable PMICs

January 15, 2020 by Cabe Atwell

Renesas’ ISL91301B PMIC is featured in Google’s Coral devices, including the Mini PCIe Accelerator, M.2 Accelerator, and SoM.

Renesas Electronics has announced the incorporation of a new PMICs (Power Management IC) in Google’s Coral AI ecosystem, which includes prototyping devices (SBC, USB accessory) and production-ready devices (SoM, PCIe modules, etc.) designed for a number of industries, including manufacturing, medical, automotive, and more.



The ISL91301B. Image (modified) used courtesy of Renesas Electronics

Google’s Coral technology offers a series of hardware and software tools aimed at advancing AI at the Edge, allowing manufacturers to develop products with machine-learning capabilities already baked within the hardware. 


What Qualifies the PMIC for Google Coral AI?

Renesas’ new (PDF) ISL91301B PMIC is designed for low-power AI processors, offering a small footprint and quad buck regulator that provides up to 4A (16A total) per continuous phase output current with 94% peak efficiency.

It also features four buck controllers and can reconfigure its power stages for said controllers, depending on the applications. Additionally, the PMIC packs Renesas’ R5 Modulation Technology, which is said to provide a quick single-cycle response, tuned compensation, and fast switching frequency to changing output load conditions.


Block diagram of ISL91301AIIZ

Block diagram of ISL91301AIIZ. ISL91301AIIZ, the sister device to ISL91301B, is a three-output PMIC while the ISL91301B is a four-output PMIC. Image used courtesy of Renesas Electronics

“We are thrilled to be collaborating with Google on their innovative, next-generation products," said Andrew Cowell, VP of the mobility infrastructure and IoT power business division at Renesas.

"Our multiphase PMIC employs Renesas’ industry-leading R5 modulation technology for a blazingly fast transient response, which allows Google’s designers to dynamically scale power to improve overall system performance.” 


Key Specifications of the New PMIC

The device offers a number of notable features, including its programmable PWM frequency of 2MHz to 6MHz. Other key features of the ISL91301B PMIC include:

  • 4A per phase for the 2.8V to 5.5V supply voltage (VIN_SEL = AVIN)
  • 3A per phase for the 2.5V to 5.5V supply voltage (VIN_SEL = GND)
  • High efficiency (93% for 3.8V in/1.8V out)
  • Low lq in low-power mode
  • ±0.7% system accuracy
  • Remote voltage sensing

The new PMICs also feature a I2C programmable output of 0.3V to 2V and an independent Dynamic Voltage Scaling (DVS) for each output. It also includes soft-start and fault detection (UV, OV, OC, OT) and short-circuit protection. 

The device has a footprint of 2.570mm x 2.919mm and features a 42 ball WLCSP with 0.4mm pitch.


Technology Behind ISL91301B

Renesas states their ISL91301B PMIC integrates low on-resistance MOSFETs and programmable PWM frequency, which allows the use of small external inductors and capacitors. It also features automatic Diode Emulation (DE) and Pulse Skipping (PS) modes under light-load conditions to increase efficiency and maximize battery life.


Dual-phase efficiency vs. single-phase efficiency

Dual-phase efficiency vs. single-phase efficiency. Image used courtesy of (PDF) Renesas Electronics

The PMIC is outfitted with a standard interrupt, chip enable, and watchdog reset functions.

Moreover, the PMIC features four MPIOs and a pair of GPIOs with I2C, SPI, and various other pin mode functions.


How ISL91301B Fits in the Google Coral Ecosystem

We've recently discussed Google's new and updated Coral hardware for 2020. By incorporating Renesas’ ISL91301B PMIC into the Coral ecosystem, Google claims that their devices gain a new level of power efficiency over similar devices currently on the market. 

Beyond the PMIC, Google’s Coral line features a number of other industry components, including MediaTek’s 8167S SoC, which hosts a quad-core Arm Cortex-A35 processor; an IMG PowerVR GE8300 GPU; and Google's own Edge TPU


Google Coral AI products

Google’s Coral devices incorporate the company’s Edge TPU (Tensor Processing Unit) along with Renesas’ ISL91301B PMIC. Image (modified) used courtesy of Google

The Coral ecosystem also includes a yet-to-be-released Accelerator Module outfitted with Renesas’ PMIC and Edge TPU, which offers either a PCIe Gen 2 or USB 2.0 serial interface. These can be incorporated into custom PCB designs.

In Renesas’ press release, Kai Yick, Google's hardware manager, stated, “Renesas’ Multiphase PMICs provide our engineering team with the high performance and design flexibility required to build Coral. Our collaboration with Renesas ensures our Edge TPU achieves the highest power efficiency to perform calculations offline and locally.” 


Applications Beyond Coral AI

Of course, it should be mentioned that the ISL91301B PMIC isn’t exclusive to Google’s Coral-based devices. The devices can be incorporated into any hardware that requires high output power and a small footprint.