Other Parts Discussed in Thread: LM5176
I have created a variant of the evm board from files previously provided in this forum, effectively so I can use it for a custom battery charging solution. First off, I own one of the EVM boards and can confirm it works very well. I have been trying to do both schematic and electrical comparisons between the EVM board when its in operation against the one I have designed.
Powering mine up I noticed that its default power usage is ~85mA@12V against the 15mA@12V on the evm board. My board is outputting at 0V at Vout. A few obervational notes:
- The input series 10Ω resistor to Vin is dropping ~800mV
- HDRV1 is showing as a noisy ground signal. Even after disconnecting all components on its net, its still sits at 0. See scope below.
- I have 2 boards built up that have the same current draw/results/issues
- When i pull the enable pin to ground, my board draws 0mA, so it appears that current is not leaking outside of the IC
- I have reflowed majority of the components at least once and tested everywhere possible for shorts
I created the following table of observations:
Pin Num | Devboard | Custom board | I/O | Function |
1 | 2.23 | 2.3V | I | Enable |
2 | 11.7 | 10.7 | I/P | Vin |
3 | 11.6 Noisy | 11.8 | I | Vin Sense |
4 | 1.69 | 1.78 | I | Mode |
5 | 0 | 0 | I | Dither |
6 | 1.21 | 0 | I | |
7 | 0 | 0 | I | |
8 | 1.16 | 1.16 | I | SoftStart |
9 | 1.39 | 3.23 | O | Compensate |
10 | 0 | 0 | G | Gnd |
11 | 0.8 | 0 | I | FB |
12 | 10 | 0 | I | Vout Sense |
13 | 10 | 0 | I | |
14 | 10 | 0 | I | |
15 | 0 Noisy | 0 | I | |
16 | 0 | 0 | I | |
17 | 7.4 | 0 | O | PGOOD |
18 | 10 | 0 | I | |
19 | 16 | 6.8 | O | |
20 | 16 | 6.8 | P | |
21 | 0 Noisy | 0 | O | |
22 | 0 | 0 | G | Gnd |
23 | 7.4 | 7.3 | I/O/P | Vcc - Out |
24 | 10 | 0 | I/P | Bias |
25 | Switching | Switching | O | |
26 | Switching | 6.8V DC | P | |
27 | Switching | 0 (Noisy) | O | |
28 | Switching | 0 (Noisy) | I |
HDRV1 output signal: scoped
Schematic PDF for better resolution: http://a.uguu.se/7pnQPFOL2gKW_LM5176Customboard.pdf