Hot Swap Controller Enhancing Data Center Reliability MCC’s Application Note AN1001
– Best Practices for Integrating TVS Diodes
by MCC (https://solutions.mccsemi.com)
May 09, 2025
Data centers are facing a critical challenge due to the rapid expansion of cloud computing services and the proliferation of Artificial Intelligence (AI). This unprecedented growth has resulted in an increased demand for data processing, which, in turn, heightens the need for robust power management systems.
A significant concern is the risk of power supply failures, which can lead to widespread system outages, resulting in data loss and substantial downtime.
To address this issue, data centers have implemented hot-swap devices that allow specific server application boards to be added or replaced without shutting down the system. However, these solutions are not enough on their own. To fully ensure reliability and protect against transient current and voltage surges, it is indispensable to incorporate Transient Voltage Suppressors (TVS diodes) into hot-swap controllers.
In this application note, we will outline a procedure for selecting an appropriate TVS device for hot-swap applications, aiming to mitigate the risks associated with power supply failures and enhance overall system reliability.
Data Center Specifications and Requirements
Data center circuits are highly complex. However, when analyzing the power supply architecture, the block diagram can be simplified for clarity, as shown in Figure 1.
Fig. 1. Block diagram 54V DC-based power supply architecture.
Traditionally, power supply systems in data centers and servers have relied on a 12V DC-based architecture. However, with the rapid increase in data management requirements and power density, the demand for higher efficiency in power delivery has become crucial. This complexity is compounded as data centers transition to a 48V to 54V DC architecture, which is now becoming standard in telecommunications and IT systems.
This shift to a higher voltage output from AC/DC converters is not merely a change in numbers – it significantly affects current flow and loss minimization, thereby improving overall efficiency. The transition reflects the multifaceted challenges data centers face in optimizing their power management systems
while accommodating growing demands.
Hot-Swap Systems and the Challenges of Transient Voltage Surges
The primary goal of data center operations is to maintain continuous activity without interruptions. To achieve this, Uninterruptible Power Supply (UPS) systems are put in place to ensure that the underlying power system remains operational under any circumstances, effectively preventing failures.
However, the DC block can experience issues such as server disconnections that are unrelated to power supply failures, leading to problems from transient parasitic inductance and capacitance effects, which create a precarious situation for data center reliability.
To manage capacitive in-rush currents, hot-swap circuits control current peaks that could damage connected servers during board swapping.
These circuits, as seen in Figure 1, safely disconnect a failed server by turning off MOSFET Q1 to avoid overcurrent damage in case of a failed load.
Still, having a proper hot-swap design will not prevent parasitic inductances from the backplane to the swap card connection to cause an inductive kickback when a faulty load is disconnected. This phenomenon occurs because the overcurrent detected by the hot-swap controller will still try to flow during load disconnection, leading to arcing risk.
To prevent damage, this overvoltage must be diverted from the circuit and discharged safely. This is why TVS diodes are indispensable. The TVS diodes must be connected in parallel with the power supply to provide adequate protection during inductive overvoltage transients. These clamping diodes will protect the system by limiting the voltage using the avalanche effect.
For Choosing an Appropriate TVS take their 9-Step Approach as described in the complete attached PDF.
