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Effect of LSCO in Analog Mode

Rob.Riggs
Senior III
Posted on June 25, 2018 at 00:59

Am am using an STM32L433 part with an LSE and wish to use the LSCO to drive a Bluetooth module's low-power oscillator input (SPBT3.0DP2's LPO) pin.  I see that the code which enables the LSCO output sets the PA2 to Analog mode.  I am running the MCU at 3.3V. The BT module LPO limits are 1.5-1.8V.  So I need to do some sort of level conversion.  After reading the reference manual and datasheet, I still don't have a good feel for the electrical characteristics of the L4's LSCO pin.

Is the output impedance characterized somewhere? I don't see that in the datasheet or reference manual.

What is the affect of setting an output pin which is not driven by the DAC to analog mode?

I am asking because I am trying to find the lowest cost and lowest power option for driving the LPO at 1.8V.  The BT module does have a 1.8V output which can be switched via a mosfet if needed, but I don't know yet♯ if I really need an active component here.

#stm32l4 #lsco
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