I'm trying to find the part numbers for FETs used in a 4in1 quadcopter ESC.
ESC information (as advertised):
- brand/model: HAKRC/HK1S
- voltage 1-2S Lipo or 1-2S HV Lipo, which translates to roughly 3.3 - 8.7 V
- current: 10 A continuous, 12 A for 5 seconds
- firmware: BLHeli_S O_L_05
The firmware variant ("O") points towards a pair of P- and NFETs for each phase, but that's not 100% sure.
There are three chips marked "SP1 645" and three chips marked "AKW 3FAB" per phase.
Doubts have come up regarding the max voltage rating, because the MCU might not be able to pull a PFET's gate high enough to fully switch it off. FETs were reported to blow up when a 2S LiPo is connected. This seems plausible because there is no additional circuitry present to drive the high side FET's gate, unless the chips aren't ordinary FETs.
I was able to trace some signals and here are my findings.
The chip labeled "SP1 645" in the first picture has direct connections to
- a motor phase output and
- the EFM8BB1's pin 8, which is P1.5. In BLHeli_S terms that's "Cc", or "phase C com FET gate output".
-> it's probably a PFET.
The chip labeled "AKW 3FAB" in the third picture, next to the black lead has direct connections to
- Bat- (or Gnd),
- the same motor phase output as the chip described above
- the EFM8BB1's pin 9, which is P1.4. That's "Cp" or "phase C PWM gate output" in BLHeli_S.
- -> it's probably an NFET.
The EFM8BB1 is directly powered from Bat+. The absolute maximum for this chip is 4.2 V, which is pretty much exactly a fully charged LiPo. The SOT-23-6 part is apparently a boost regulator because
- it sits opposite to a large inductor labeled "100" and a diode labeled "K34"
- the ESC has 5 V output on a pin labeled "5V" even if it is only supplied with a lower voltage through Bat+
The connections found so far support the impression that this ESC can't handle anything above 4.2 V. The FETs might be able to, but the whole ESC can't.