We are targeting a very compact design. Thus, we have two questions for the external circuits of the DA14580/14581:
1. Do we have to use the 16Mhz Crystal? There is 16Mhz RC oscillator inside the silicon, can we use that instead? Can we also use external 16Mhz clock source to replace the crystal? Same question also applies to 32kHz clock source as well.
2.For the power supply of the chip. Can we skip the Buck converter to save the space of the bulk inductor? Instead, we plan to use two regulated power rails to supply VBAT and VDCDC, is this doable?
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HI,
Here's the comment to your question.
1. The tolerance of internal 16MHz RC oscillator is high and thermal sensitive. It is not recommended for TDMA/TDD BLE application which requires accurate time base for synchronization. The external 32KHz can be skipped and use the internal 20K RCX oscillator instead for sleep mode. External 16MHz clock source can be used but the power consumption will certainly go up.
2.巴克转换器是将the VBAT voltage to 1.4V to feed the internal LDOs to generate a 1.2V regulated voltage for core and peripheral. It is recommended to keep buck converter as the current consumption in the idle or sleep mode will be the best as the quiescent current for external LDO and DC/DC is quite high. The LDO for VBAT input should not have any problem as long as it is operated above 2.4V for OTP option.
Regards, WC Ip
We are not too concern about the current consumption but cares about the size of the whole solution. That's why we want to skip the buck converter to save the bulk inductor space. So basically, we can use two separate rails: >2.4V and 1.4V to power on the chip, right?
Hi,
Theoretical yes, but you need to verify on the bench based on your own design . Beware of the power up sequence, VBAT1V to GND, VBAT3V before VDCDC when ON.
Regards, WC Ip
regarding below:
1. The tolerance of internal 16MHz RC oscillator is high and thermal sensitive. It is not recommended for TDMA/TDD BLE application which requires accurate time base for synchronization
in my project, we use broadcast and observer mode only, that means some devices may send non-connectable advertise and other devices will listen or observe the advertise, but not connect to them, so can we use the internal 16MHz RC ?
Hi achao1104,
You cant just use the RC16 to operate your bluetooth even if you dont establish connections. The BLE communication frequency is depended on the XTAL, you wont be able to transmit BLE packets in the appropriate frequencies since your RC16 will drift.
Thanks MT_dialog
got it.