WIZnet Developer Forum

W7100A Chip on WIZ107SR Module Get Very Very Hot

Dear WizNet Tech Support and all,

Recently we bought about 25++ pcs Wiz107SR (TTL & 232 version) from wiznet local distributor in Indonesia.

We use Wiz107SR in an IoT-based energy monitoring system and the device demands to run 24/7 and our device life expectation is 5 years.

The problem we face is the W7100A gets very hot (around 50 deg C) in an open space (room temperature) several minutes after power on. At this point it didn’t affect the device’s performance (data transmission works flawlessly, we able to ping, etc). We already read some of old post that as PHY chip, its normal for W7100A to get hot (around 40 - 50 deg C) when in operation.

But, when the PCBs placed inside its casing (casing size is about 100x80x60mm) [color=#FF0000]the W7100A chip is get very very hot[/color] (it should reach 80 deg C) several minutes after power on. At this point the [color=#FF0000]device is stop working[/color] (no data transmission, unable to PING, and didn’t appear in in the config tool).

Here is some action we already taken to reducing the W7100A’s heat (all of it didn’t work) :

  1. Place an heat sink on top of the chip => Not Working, the heat sink became untouchably hot to
    heat sink reference :
  2. Setting the inactivity timer to 10 second (Our cloud server is collecting data from the device every 5 minutes) in order to put the W7100A to idle / sleep when no data transmission activity => Not Working, the chip still get hot
  3. Experimental : holding the Wiz107SR reset terminal low for several minutes to see if it reducing the heat => Not Working, the heat not reduced
  4. Place an 100nF ceramic capacitor to +3.3V and 0V terminal at the module to reduce voltage ripple (if any) => Not Working

[color=#FF0000]The problem is appear in every single Wiz107SR we bought.[/color]
Can you tell us how to deal with this heating problem or how to reduce the heat of the W7100A chip?

Here is some technical info about how we use the Wiz107SR module :

  • Main Power Input : +24 VDC
  • Main Regulator IC : LM2596-5.0 (convert +24VDC to +5VDC)
  • Regulator IC for Wiz107SR : AMS1117-3.3 (Convert +5VDC to +3.3VDC)
  • Voltage to Wiz107SR is measured around 3.2 - 3.3 VDC
  • Wiz107SR Serial Baudrate is set at 9600 - 19200

Let us know if you need further details to analyze the issue.
Any help or suggestion is really appreciated.

Thank You in Advance

Best Regards,
Pramudita Johan Iswara

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