W5100 Current Consumption Problem

Question

Hi, I am using the circuit as attached. It appears something on the 3V3 supply of pin 2 is drawing too much current such that it pulls down the 3V3 supply to somewhere around 1.7V. When I remove L1 the digital supply goes to 3V3.W5100 Module.pdf (34.6 KB)

Eugeny · Answer

Imagine the current flowing through this ferrite bead! There are only two possibilities - current flowing through pin 2 of the chip - thus chip is defective - or current flowing through magjack circuitry. I would start with second possibility, checking magjack circuit and looking for short circuits, for example one of C19 or C20 shorted thus making current flowing through magjack coil and 49.9 Ohm resistors.

neilbadenhorstgmail · Answer

Thank you for the quick response. I disconnected power supply to Pin to of the W5100 (by cutting a track) and the power supply now measures 3V3 as expected. Something must be wrong then with the chip however also tried on another PCB and have the same problem. Any ideas ?

neilbadenhorstgmail · Answer

Ok fixed cut and wire so power back on pin 2. Then removed connector with magjack circuitry completely. Seems good power is 3V3 as expected. The circuit in schematic draws 60mA though. Seems too much as datasheet for W5100 says 5mA and all LED’s are off. Any ideas ? Also on magjack connector ? Using magjack: https://www.digikey.com/products/en?keywords=732-4495-5-ND

neilbadenhorstgmail · Answer

Ok removed C19, C20 and even C22, R9 and R16. So problem still exists and is around R10 R12 and R13 R14 and magjack connector as you said.

neilbadenhorstgmail · Answer

Yes magjack is wired on the board the same way as per schematic. I assume the magjack is genuine yes, bought from Digi-Key: https://www.digikey.com/products/en?keywords=732-4495-5-ND Regulator rated 150mA. However datasheet for W5100 says 5mA and all LED’s off. Maybe I’m wrong on that and the W5100 together with magjack needs more than 150mA, or perhaps rather only the magjack as everything was powering up when removed the magjack. When I remove the magjack the board draws 56mA current. With magjack in place the board briefly draws around 140mA with regulator at 3.3V then voltage drops to around 1.8V and current measures around 80mA. Putting it straight to a bench power supply at 3V3 draws way more current. Think it must be on pins 4 and 7 (3V3A) on magjack else something would surely have blown. Also hear singing when power on.

neilbadenhorstgmail · Answer

Eugeny: ratings Yes under number 7. page 64 it says DC input current +/- 5mA. Is this wrong ? Sorry I made a mistake. Swapped the wires. Placed the board on a bench power supply and it draws 146mA in total. So it must be the regulator not having enough juice. Does this amount of current consumption sound right ?

neilbadenhorstgmail · Answer

Thanks a lot for all your help. Will replace regulator and see how the programming goes…

neilbadenhorstgmail · Answer

Hi, I have a new issue on some of the PCB’s. Everything works fine for a a while and then stops. All LED’s etc goes off. This is only on 2 out of 7 PCB’s so far. When I then press a multi meter positive terminal onto the 3V3 digital supply eveything coms to life and is happy while a hold the probe there. The negative probe is not even grounded. Pic attached. new regulator used: NCP1117LPST33T3G W5100 PCB4096×2304 1.42 MB Please help ?