Consider the following points before starting the
TPS7H3302 layout design.
- The input bypass capacitor for VLDOIN should be placed as close as possible to the pin with short and wide connections.
- The output capacitor for VTT should be placed
close to the pin with short and wide connection in order to avoid additional ESR and/or
ESL trace inductance.
- VTTSNS should be connected to the positive node
of VTT output capacitors as a separate trace from the high-current power line. This
configuration is strongly recommended to avoid additional ESR and/or ESL. If sensing the
voltage at the point of the load is required, it is recommended to attach the output
capacitor or capacitors at that point. Also, it is recommended to minimize any additional
ESR and/or ESL of ground trace between the GND pin and the output capacitor or
capacitors.
- Consider adding low-pass filter at VTTSNS if the
ESR of the VTT output capacitor or capacitors is larger than 2 mΩ.
- VDDQSNS can be connected separately from VLDOIN. Remember that this sensing potential is the reference voltage of VTTREF. Avoid any noise-generating lines.
- The negative node of the VTT output capacitor or
capacitors and the VTTREF capacitor should be tied together by avoiding common impedance
to the high-current path of the VTT sink and source current.
- The GND and PGND pins should be connected to the thermal land underneath the die pad with multiple vias connecting to the internal system ground planes (for better result, use at least two internal ground planes). Use as many vias as possible to reduce the impedance between PGND/GND and the system ground plane. Also, place bulk caps close to the DIMM/module or memory load point and route the VTTSNS to the DIMM/module load sense point.
- In order to effectively remove heat from the
package, properly prepare the thermal land. Apply solder directly to the package’s thermal
pad. Numerous vias, 0.33 mm in diameter or smaller, connected from the thermal land to the
internal/solder side ground plane or planes should also be used to help dissipation.