Hi,
I am using a nRF51822 board and I wanted to know if the LC filter is necessary if I don't need to use any analog entrance or exit. I just need the BLE and a digital input.
Hi,
I am using a nRF51822 board and I wanted to know if the LC filter is necessary if I don't need to use any analog entrance or exit. I just need the BLE and a digital input.
Which LC filter? AFAIK there is one on the antenna and one for the DCDC. The LC on say pin DEC2(?) is for the internal DCDC power supply (not sure I would call it a filter?) Whether you need that depends on your external voltage source greater than 2.1V (the min the DCDC requires) and whether you want the efficiency of the DCDC (vs LDO.)
If my voltage source is above 2.1V (3V for example) do I need the internal DCDC or I can work with the LDO?
The nRF51822 has a internal LDOs that powers the System, Peripherals, Flash, the Radio etc. It also has an internal DCDC that can be enabled to reduce the current consumption of the Radio substantially, see Section 8.5.3 in the nRF51822 Product Specification, found here. However, this requires some additional external components which are shown in the reference circuitry also found in the PS.
The DCDC requires at least 2.1V. The LDO requires any voltage in the chip range (1.7-3.6V).
As Bjorn's answer states, the DCDC is more efficient but requires external components (what you are calling an LC filter.)
Typically you would use the DCDC if your power supply was a small coin battery and you want long battery life.
Actually my power supply is not a battery, so I don't have battery life problems.