BQ77905: 20 Series Schematic, Use of NET tie.

Nishchay Kathuria

Part Number: BQ77905

hey! I was making a schematic for 20 series protection circuit and taking reference of the 20 cell configuration. Kindly suggest what is the need for the net tie, in the bottom left corner of the schematic.

https://www.ti.com/lit/an/slua774a/slua774a.pdf?ts=1597503294888&ref_url=https%253A%252F%252Fwww.google.com%252F

Also, can you please suggest, for what current rating is this given schematic safe to operate?

thanks and regards.

over 5 years ago

0 Matt Sunna over 5 years ago

TI__Guru* 81035 points

Hi Nishchay,

A net tie is a layout feature to provide a single connection point between the high current path and the low current reference point. It is explained a little better in this thread and also here is a link to the Altium reference document.

https://e2e.ti.com/support/power-management/f/196/t/437630

https://smtnet.com/library/files/upload/NetTies-and-How-to-Use-Them.pdf

The current rating depends on the components used. The BQ77905 is only sensing the voltage across the sense resistor. FETs and the the sense resistor should be selected to ensure they can handle the current levels you need. Some users choose to use multiple resistors in parallel and multiple parallel FETs can also be used. Here is a good app note on using multiple FETs for higher current: https://www.ti.com/lit/an/slua773/slua773.pdf

Best regards,

Matt

Power management

Power management forum

BQ77905: 20 Series Schematic, Use of NET tie.