I received the TDA4VM Edge AI starter kit in the post a few days ago. The kit is supplied without a power supply, so in this quickfire post I'll present some of my thoughts and ideas on powering the board on a budget.
One of the recommended power supplies is a wapping 20V 65W AC/DC desktop class supply, costing about £23 + VAT + Postage and Packing in the U.K.
Can we use something cheaper like a Universal USB-C power supply used with the Raspberry Pi 4. Let's find out.
The TDA4VM starter kit can accept a wide range of input voltages, although the recommend power supplies are 20V Type-C; capable of supplying up to 60W of power (20VDC at 3A). However, as can be seen in the screenshot, below, the nominal voltage output from the USB-C Type connector is 5-20VDC with a maximum output current of 5000mA. Hence, there is quite some flexibility, as to the power input supply that can be used, depending on how the starter kit is operated.
N.B If USB peripherals are used with the starter kit, then they "require VBUS and depending on their power needs, may have too much voltage drop from a 5 V input supply. This is a reason higher voltage supply is recommended. There are many USB Type C power supply manufactures and models available in the market, and it is not possible to test the EVM with every combination", this according to the user manual.
The list of recommended power supplies are shown in the screenshot image, below.
Power Budget Considerations
The functional block diagram, seen opposite, is of the power input supply. Here, it can be seen that the power input is fed to a USB Type-C controller and Power Delivery (PD) manager, the TPS25750.
From this device the power is distributed, firstly, to the LM61460, a low-EMI synchronous step-down converter, configured to output 5V.
Secondly, the power from the Type-C controller is supplied to a 3.3V buck regulator (LM5141RGET) and onto a Power Management Integrated Circuit (PMIC), which regulates the power supplies to the TDA4VM processor.
An EEPROM is used to configure the PMIC, as well as Wake-up the processor. This setup seems to offer amble protection to the starter kit processor and one would expect that the PD controller prevents external peripherals from drawing too much current from the input power. The USB type-C can only supplies power.
The functional power requirements of the major elements of the starter kit are listed in the screenshot image, below.
One can deduce from the listing above that a smaller and cheaper supply could be used, when a limited number of external peripherals are enabled. Also, the processor would not be expected to operate at its maximum capacity. Then, it should be possible to drive the kit with a Raspberry Pi type power supply, like the one shown in the image, below. This is a much cheaper solution than the official supplies and may be enough to drive one or two external cameras. I will be getting one of these soon and will report back my findings in an upcoming article.
SK-TDA4VM User's Guide SPRUJ21A – AUGUST 2021 – REVISED SEPTEMBER 2021, Texas Instruments