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STMicroelectronics STM32MP157A-DK1 Discovery Kit

In the video below, I take you through some of the fun features of the STM32MP157A-DK1 discovery kit from STMicroelectronics. We also take on the world of power management with the STPMIC1.

Here is the link to the STMicroelectronics Wiki page. Don't be confused that the description is for the STM32MP157C-DK2, which simply has a few extra features over the DK1.

ST Discovery Kits

The STM32MP157A-DK1 and STM32MP157C-DK2 Discovery kits allow users to easily develop and try out applications on the STM32MP1 Series microprocessors using the STM32 MPU OpenSTLinux Distribution software for the Arm Core A7 main processors and STM32CubeMP1 software for the Arm Core M4 co-processor.

The boards include an ST-LINK embedded debug tool, LEDs, push-buttons, a Gigabit Ethernet connector, a USB Type-C™ OTG connector, four USB Type-A Host connectors, one HDMI® transceiver, a stereo jack with analog microphone, and one microSD™ connector.

Expanded functionality is supported through GPIO expansion connectors for ARDUINO® shields and Raspberry Pi® HATs.

The STM32MP157C-DK2 Discovery kit features an LCD display with a touch panel and Wi‑Fi®/Bluetooth® Low Energy capability.


Power Management

What do you get when you pack six low-dropout (LDO) regulators, four DC/DC buck converters, and one boost DC/DC converter into a 5mm x 6mm x 0.8mm WFQFN package? If you ask ST, it’s a power management chip called the STPMIC1.

Block diagram of the functionality of the STPMIC1

The device is optimised for the STM32MP1 MPU’s featured in our video above, but (with 14 output rails) could easily be used to support many other applications that feature an MPU with multiple peripherals.

STM32MP1 MPU’s features

So, let’s answer the obvious question first: why would I want this in my system?

I would say there are two main reasons:

  1. Board real-estate: the external parts required to provide each power rail are reduced to 3 passives for the DC/DC converter lines and only 2 for the LDO lines. Pretty useful, when space is at a premium.
  2. Programmable control: an I2C interface and digital I/O to control and monitor power rails – all of which are protected against short-circuit and overcurrent conditions.

The STPMIC1 is designed to operate with input voltages ranging from 2.8V to 5.5V, supplying stable power to external memory and peripherals as well as the host MPU. This gives hardware designers easy options to power applications from Li-Ion or Li-Po batteries as well as 5V adaptors or USB.

Four Bucks, One Boost Converter and Six LDOs

The four buck converters switch at a base frequency of 2 MHz and are built around an adaptive constant on-time (COT) controller to guarantee excellent transient response and precise output voltage control. Each buck has up to 90% efficiency across the whole voltage range thanks to a low-power PFM mode that smoothly transitions to PWM for normal operation. Each PWM is synchronised with a 90° phase offset to the neighbouring buck (using an integrated phase-locked loop) which reduces the instantaneous power draw from the supply and reduces EMI.

The single boost converter also has a 90% efficiency and can supply 3 USB ports.

Features of Buck Regulator and Boost Converter

The linear voltage regulators include four general-purpose LDO’s, two of which are identical. The other two LDOs include one that can supply a higher maximum voltage and another that can supply a lower minimum voltage.

There is also a fixed LDO aimed at supplying the physical layer of the processor’s USB interface and a final LDO with three operating modes: a standard LDO mode, a sink/source mode for powering DDR2/3, and a bypass mode for Low power DDR2/3. There is also an auxiliary output to supply a stable reference voltage to DDR memory.

Features of the LDO

The final two outputs are the power load switches. SW1 is compliant with USB On-The-Go (OTG) and USB type C dual role data (DRD) and has VBUS detection allowing USB connections in host and device modes. SW2 is general purpose and can be connected to an external source or the output of the boost converter.

Switch features


The STPMIC1 is an I2C bus slave that can operate at all speeds up to fast-mode+ (1Mb/s). Along with the control lines, this allows the processor to control and monitor the regulator configuration, power modes, interrupts, protection etc.

Non-volatile memory allows storage of default output voltages, start-up sequences, protections and the I2C address. There is also a lock bit to prevent tampering. The device can be bought with pre-programmed settings for the start-up sequence and voltage settings, there is also a version with no programmed settings (STPMIC1C) for generic applications:

Table for STPMIC1A pre-programmed settings for the start-up sequence and voltage settings

Evaluation Kit

If this all sounds like something you would be interested in finding out more about, here is a STPMIC1 DATASHEET.

If you are interested in investigating it for yourself, there is an evaluation kit, the STEVAL-PMIC1K1 (208-5069) .

Top level image of the STEVAL-PMIC1K1

The eval board kit includes a USB dongle that provides I2C access to the STPMIC1 configuration registers and header connectors for external access to the embedded regulators and switches in the device. This lets you really get to grips with the programmable converter power-on and power-off sequences, I2C control, and non-volatile memory configuration storage.

Mark completed his Electronic Engineering degree in 1991 and worked in real-time digital signal processing applications engineering for a number of years, before moving into technical marketing.
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