4 Output Voltage Clamping with TPS2352x

Traditional hot-swap design has a limitation of excessive SOA stress on the hot-swap FET in case output needs to be powered under over-voltage conditions.

The proposed design uses TPS2352x to address the SOA problems. As shown in Figure 4-1, the voltage clamp design adds one feedback loop using an op-amp to the traditional hot-swap design and uses the over-voltage lockout (OVLO). OVLO is typically set by the input voltage node, however, in the proposed design the OVLO signal is fed back from the floating supply output node. Once the OVLO signal trips, the hot-swap controller can turn off the pass-FET immediately and limit the output voltage at the target to 62.5V. With the floating supply output powering the downstream system, C_OUT is discharged and the OVLO signal also goes below the threshold turning back the pass-FET ON again. This repetitive process clamps the output voltage as shown in Figure 4-2. This brings system benefits by lowering C_OUT by 80% and reducing SOA stress by 55% compared to the traditional hot-swap design.

Figure 4-1 Hot-Swap Circuit with Clamping Scheme on Floating Supply Output

Figure 4-2 Conceptual Waveforms During 75V/10ms Over-Voltage Event in the Proposed Design