Using AFE4404 with STM32F4Dsicovery

carlogulliani · ‎2016-04-25

Posted on April 25, 2016 at 20:35

I have a question about using TI AFE4404 with STM32F4Disco. My question about power supply. I found in datasheet, that

Supplies: Rx: 2 V to 3.6 V, Tx: 3 V to 5.25 V, IO: 1.8 V to 3.6 V

And description of theirevolution board where they describe power solution:

AFE4404 can operate from 2.0-V to 3.6-V Rx analog supply (RX_SUP), 1.8-V to 3.6-V IO digital supply(IO_SUP), and 3.0-V to 5.25-V Tx Control supply (TX_SUP).<
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>The power for the board is derived from the USB input (J1) through a forward-biased diode (D1) to avoidreverse current flow. The USB data bus is ESD protected using TI’s ESD protection diode array<
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>TPD4E004DRYR (U5). The USB VBUS is fed to the integrated Li-Ion linear charger and systempower pathmanagement module, bq24032ARHLR (U3), which generates greater than 4.2-V output (VCC_BAT).<
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>This output is fed to TI’s low-input boost converter with integrated power diode and input/output isolation,TPS61093 (U7), for generating a boosted voltage of 8.97 V. This output is fed to low-noise voltageregulator LP3878-ADJ (U9) for generating 5 V for TX_SUP. The VCC_BAT is also fed to the ultralownoiselinear voltage regulator TPS7A4901DGN (U6) for generating 3 V for the MSP_DVCC, MSP_AVCC,RX_SUP and IO_SUP.<
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><
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>Series jumper resistors are provided to make sure the power supplies to the board are correct.

So, stm32 has +5V pin and +3V pin, do I need those ICs I described above to use with AFE4404 or it's enough to use stm's pins for this one? #stm32 #afe4404

re.wolff9 · ‎2016-04-26

Posted on April 26, 2016 at 11:12

Usually power supply specifications allow for a 10% difference from the normal value. So if you see 2.7-3.6V they mean that the chip can run at 3.0 or 3.3V nominal, where the 3.0V can be allowed to drop as low as 2.7V and the 3.3V can be tolerated as high as 3.6V.

In your case the manufacturer only allows a +5% on the 5V spec. So you see 5.25V. Fine.

For your TX the spec says 3.0-5.25V. That means they expect you to use 3.3V or 5.0V, NOT 3.0V.

I don't know that chip you're talking about, I haven't checked it out. Just using the information you posted.

carlogulliani · ‎2016-04-26

Posted on April 26, 2016 at 11:40

And what are the current sourcing capabilities of the +5V and +3V pins of STM32 device?

The AFE can draw high switching currents from the TX_SUP pin. Is the +5V pin of STM32 capable of sourcing the switching currents?

michaelc.barton9 · ‎2016-04-26

Posted on April 26, 2016 at 13:04

Please take a look at the STM32 Discovery Board User Manual (PDF)

The 5v supply is dependent on how the board is powered. If it is plugged into computer USB, then that is what your computer will allow, otherwise it is limited by your battery/PSU

The 3v supply comes from onboard LDO Vreg LD3985 which can supply up to 150mA

just plugging in my board, I see it draws ~80mA, and most of that would be drawn by the 3v peripherals

carlogulliani · ‎2016-04-26

Posted on April 26, 2016 at 13:38

so than, it's better to have an additional power supply for this as they recommend, is it? And one more question, this chip uses I2C interface for communicating. But it has 3 more pins instead of SCL and SDA for output: RESETZ, Analog CLK and ADC_RDY.

I guess ADC_RDY is gpio, which allows me to check the status of chip's internal ADC, RESETZ probably too, but how can I connect this Analog CLK to stm32f4discovery, I mean do I need to connect it directly to crystal of 8MHz or there is another way?