12.1 Layout Guidelines
When doing the layout of the TPS2474x in the ORing then hot swap configuration the following are considered best practice.
- Ensure proper Kelvin Sense of RSNS
- Keep the filtering capacitors CFSTP and CRV as close to the IC as possible.
- Keep the traces from CCP to CP and A as short as possible.
- Run a separate trace from A and RVSNM to ORing FET source. This will prevent the charge pump noise along with a DC bias (due to supply current draw) from interfering with the reverse current threshold.
- Run a separate trace from C and from RRV to ORing FET drain.
- Place a Schottky diode and a ceramic bypass capacitor close to the source of the Hot Swap MOSFET.
- Place a TVS and a ceramic bypass capacitor between VIN and ground close to the source of the ORing MOSFET.
- Use a separate trace to connect to VDD and SENM.
- Note that special care must be taken when placing the bypass capacitor for the VDD pin. During Hot Shorts, there is a very large dv/dt on input voltage during the MOSFET turn off. If the bypass capacitor is placed right next to the pin and the trace from RSNS to the pin is long, an LC filter is formed. As a result a large differential voltage can develop between VDD and SENM if there is a large transient on Vin. This could result in a violation of the abs max rating from VDD to SENM. To avoid this, place the bypass capacitor close to RSNS instead of the VDD pin.