To minimize nRF51822 power consumption, what is best operating voltage either 3.3V with internal DC/DC enabled or external DC/DC 1.8V?
To minimize nRF51822 power consumption, what is best operating voltage either 3.3V with internal DC/DC enabled or external DC/DC 1.8V?
Hi
I suspect that would depend on the specifications for a chosen external DC/DC. The problem with DC/DC is that it requires some current to operate, so if you do not have a high current consumption, it does not pay off to enable it. For the internal DC/DC of the nRF51, it is only enabled during radio activity, but the radio normally contributes to the majority of the overall current consumption.
I also suspect there is some overhead in figuring out when to enable an external DC/DC, in order to not have it enabled when not needed or when it is insufficient, but also to ensure that it is enabled early enough in order for the supply voltage to be stable before the radio starts. Unstable supply voltage may effect radio performance, which was the problem with with the nRF51 internal DC/DC on revision 1 and 2 in combination with BLE softdevice prior to version 8.0.0. More explanation on this thread. Furthermore, Nordic can not guarantee that an external DC/DC will operate sufficiently with the radio. The radio requires fairly stable power supply.
In short, external DC/DC will cost you BOM and some time to integrate with the nRF51. I also doubt it can deliver better performance than the internal nRF51 DC/DC. I know there were some customers that used external DC/DC with revision 2 nRF51 when it was not recommended to use the internal DC/DC with softdevice. I have not heard of any interest for it after nRF51 revision 3 + S110 v8.0.0 was released, which enabled the internal DC/DC with softdevice. Perhaps others can step in if they have any further experience on usage with external DC/DC with nRF51.
Hi
I suspect that would depend on the specifications for a chosen external DC/DC. The problem with DC/DC is that it requires some current to operate, so if you do not have a high current consumption, it does not pay off to enable it. For the internal DC/DC of the nRF51, it is only enabled during radio activity, but the radio normally contributes to the majority of the overall current consumption.
I also suspect there is some overhead in figuring out when to enable an external DC/DC, in order to not have it enabled when not needed or when it is insufficient, but also to ensure that it is enabled early enough in order for the supply voltage to be stable before the radio starts. Unstable supply voltage may effect radio performance, which was the problem with with the nRF51 internal DC/DC on revision 1 and 2 in combination with BLE softdevice prior to version 8.0.0. More explanation on this thread. Furthermore, Nordic can not guarantee that an external DC/DC will operate sufficiently with the radio. The radio requires fairly stable power supply.
In short, external DC/DC will cost you BOM and some time to integrate with the nRF51. I also doubt it can deliver better performance than the internal nRF51 DC/DC. I know there were some customers that used external DC/DC with revision 2 nRF51 when it was not recommended to use the internal DC/DC with softdevice. I have not heard of any interest for it after nRF51 revision 3 + S110 v8.0.0 was released, which enabled the internal DC/DC with softdevice. Perhaps others can step in if they have any further experience on usage with external DC/DC with nRF51.
