NB-IoT-BC660H-ANT Rev D — power design question

[Dijkmeneer]

Hi all,

I'm posting this in the Arduino section since I found an older thread here about the NB-IoT BC66 module (the "Security mode change issue" thread) where LubOlimex replied — figured this was the closest existing home for NB-IoT-related questions since there doesn't seem to be a dedicated category.

I recently got an NB-IoT-BC660H-ANT board via DigiKey. The PCB silkscreen reads "Rev D," and the module soldered on it is a BC660K-GL (confirmed by reading the chip marking directly). The board also has a populated NETLIGHT LED, and the silkscreen at that pin position is labeled NETLIGHT rather than GPIO6, both of which match BC66's pin function at that position rather than BC660K-GL's. I'm assuming the board layout was carried over unchanged from before the BC66→BC660K-GL module swap (Olimex's blog confirms that transition happened), but I'm curious whether that LED still does anything meaningful with BC660K-GL populated, since that pin is just GPIO6 on this chip rather than a dedicated network-status output.

Separately — the thing I haven't been able to figure out: Olimex's product page FAQ mentions that starting with hardware revision E, the design was optimized for low-power operation by removing a voltage translator and regulator present in older revisions.

Does Rev D already include that optimization, or does it still have the older, higher-current design?
Is there any chance someone could share the Rev D schematic? I've only found Rev B and Rev E published online.

I'm building a battery-powered prototype, so the sleep-current characteristics of my specific board matter for planning battery life.

Thanks in advance for any help!

[LubOlimex]

This is not very surprising since we just recently switched to revision E of NB-IoT-BC660 boards. Boards from hardware revision E has different print on the PCB that says "NB-IoT-BC660 Rev. E" at the bottom. Based on your description I believe you received the hardware revision D board.

Both revision D and revision E designs use the same main chip BC660K-GL.

Revision D still uses the regulators. Power consumption in deep sleep is the main difference between revisions. The current consumption in deep sleep is minimum around 125uA when powered from external power source and around 85uA when powered from battery. The extra current comes mainly from the AP1231 regulator and two TXB0108 level translators. Aside from that they behave the same. Revision D board is still completely fine.

Comparing revision D to revision B the changes are unnoticeable for the customer (one is not even visible in the schematic). There are only two changes:

1. Revision C:

Changed the the sim card holder with SIMNANO-6P-1.3H, this required some other components to be moved to fit.

2. Revision D:

Updated the module package for better soldering.

My advice for future purchases is to ask beforehand about the hardware revision available.