Other Parts Discussed in Thread: TPS55165Q1-EVM
Hello,
I have an issue with voltage output in boost mode, input voltage 8V-112V, output12V
my layout is similar to the demo board TPS55165Q1-EVM except for the VREG_Q, VREG, VOS_FB pins
the capacitor Cvreg is further from pin 11 and pin 11 corrects directly to pin 12, and then to pin 14
PCB rework:
I tried to cut a trace and place Cvreg directly to pin 11 and gnd, then run a short wire lead from pin 12 to Cvreg and another wire from pin 14 directly to Cvreg
doing this improves the voltage (nice clean 5V) on pin 11 (VRER_Q) and boost functions, but under load (approx 200mA) output voltage drops to 10.7V
Here's some measurements that we've done:
Vin 8-10.5, output = 12V, loading with 55 ohm drops output to 10.7V
Vin 10.5-11.5, output = 11V, loading with 55 ohm drops output to 10.7V
Vin 11.5-32, output = 12V, no issues with loading
other difference from demo board noted:
- we use 1oz copper, on another post someone mentioned 2oz is required
- PG is left floating, but data sheet says that it must be pulled up to 5V when Vout is 12V, but demo board has it pulled to Vout (12V)
- input and output bulk caps, we have same total capacitance, the 10uF/50V we use are electrically same except for physical size, demo board uses CGA9N3X7R1H106K230KB, we use UMK325AB7106KMHT, does that make a difference?
