4 ms·
It’s a typical thing in industrial design to conduct the heat to metal enclosure. I did this for transistors in a stepper motor driver and for FPGA designs. The
by lnsru 7y ago
It’s a typical thing in industrial design to conduct the heat to metal enclosure. I did this for transistors in a stepper motor driver and for FPGA designs. The cost of conductive sheet is close to zero compared to possible problems. Lenovo saved this 0,2 cent drop of thermal paste. Maybe it’s worth producing thousands of consumer devices, though I would like to buy properly designed products.
Edit: thank you for explanation. This was not thermal problem then. I am just curious why didn’t all laptops had this problem?
- omgtehlion 7y agoI would refer you to comment by mindslight down here. It is just bad design by Lenovo. You should not put a switching transistor in linear mode. That rc-dampener is just bullshit.
- laydn 7y agoThat circuit appears to assume that AUDIO_PWR_EN signal will switch very infrequently. If AUDIO_PWR_EN is a pin that is controlled by software, and, if you keep switching that pin such that the MOSFET is kept in the linear region due to the RC on the gate, that MOSFET will be toast very quickly.
- rzzzt 7y agoThis is intended to be a power saving feature; if enabled, audio detection will be driving the enable pin with a few seconds of hysteresis: http://www.thinkwiki.org/wiki/How_to_enable_audio_codec_power_saving http://www.thinkwiki.org/wiki/How_to_enable_audio_codec_powe...
- segfaultbuserr 7y agoNow the problem is, why would a MOSFET be destroyed even if there is a few seconds of hysteresis?! Well, defective driver is a still possibility, but perhaps it's a hardware problem.