Other Parts Discussed in Thread: LM5171
Tool/software:
Hi,
I’m using two LM5171 controllers in parallel to build a Li-ion cell cycler capable of up to 100 A. The setup generally works well, but I’ve run into an intermittent issue when discharging.
Here is an overview of the system:
-
Paralleling scheme:
-
DCDC1 channel 1 uses a 10 mΩ sense resistor (for low-current accuracy).
-
The other three channels use 680 µΩ sense resistors.
-
-
Control logic:
-
≤ 2 A → only DCDC1 channel 1 enabled.
-
2–20 A → whole DCDC1 (all channels in that block) enabled.
-
20 A → all 4 channels (both DCDC blocks) enabled.
-
-
Operating mode: FPWM mode.
-
ISET: Shared across all channels, correctly set.
-
VIPK: 0.795 V.
The problem I'm encountering is the following:
-
Charging: Always works fine.
-
Discharging:
-
At > 2 A, discharging sometimes fails if it is the first operation after enabling the DCDCs.
-
If a charge cycle has been performed first, subsequent discharges work reliably.
-
When the problem occurs, the output current is lower than commanded (never reaches the target, but remains constant)
-
-
Regardless of the operation, the registers always report a bootUV error flag on all channels (both when the system works correctly and when it doesn’t). However, I've measured all 4 bootstrap capacitors and they were all at 8.34V.
Do you have any ideas what the problem could be?
