Other Parts Discussed in Thread: TPS51120
I designed a circuit around the TPS51120 for my 5V0 and 3V3 power source. I prefer the "current mode" as it has a low ripple.
The board wouldn't power up and now I'm trying to reproduce the same on the EVM.
I'm using the TPS51120EVM, and the configuration is as shown below.
1 - VO1 - NC
2 - COMP1 - NC
3 - VFB1 - NC
4 - VREF2 - 2V0
5 - GND
6 - VFB2 - Wired to VFILT5. For default 3V3 output.
7 - COMP2 - RC to GND. (10K and 1nF)
8 - VO2 - Wired to Output (Ch2)
9 - EN5 - Floating. Enabled.
10 - EN3 - Floating. Enabled.
11 - PGOOD2 - Pulle dup to VFILT5 (100K)
12 - EN2 - Floating. Enabled
13 - VBST2 - 0.1uF cap to LL2
14 - DRVH2 - 5.1Ohms to High side gate.
15 - LL2 - Drain of Low-side MOSFET
16 - DRVL2 - Gate of the low side gate.
17 - PGNG2 - GND
18 - CS2 - 15mOhms sense resistor.
19 - VREG3 - NC
20 - V5FILT - 4ohms to VREG5 and 1uF to GND
21 - VREG5 - 5V0 - 10uF to GND
22 - VIN - 12V. 1uF to GND
23 - CS1 - NC
24 - PGND1 - GND
25 - DRVL1 - NC
26 - LL1 - NC
27 - DRVH1 - NC
28 - VBST1 - NC
29 - EN1 - NC
30 - PGOOD1 - NC
31 - TONSEL - GND/VFILT5
32 - SKIPSEL - GND/VREF2
33 - PwPd - GND
In the first step, I'm trying to generate the 3V3 output. I have an LED at the output. The VIN is 12V.
When in enable EN2, The LED just blinks. Probably goes into the fault condition. I read close to 4.65V when I set the JP2 to "Fault-Off" setting.
Is there a working reference design for the 5V0 and 3V3 in the current mode? Did anyone else have a similar stability issue?
Any help will be greatly appreciated.