حفاظت مدار محدودکننده‌های ولتاژ گذرا (تی وی اس) تجهیزات حفاظت در برابر اضافه‌ولتاژ گذرا (اس پی دی)

Product Attributes

Introduction

The MIC2596 and MIC2597 are dual-channel negative-voltage hot-swap controllers designed to facilitate the safe insertion and removal of PCBs into and from live backplanes. To minimize external components, each channel of the MIC2596/MIC2597 integrates a high-voltage power MOSFET. The built-in current sensing in each channel provides inrush current limiting by regulating the channel's output current to a user-programmable maximum. Current sensing also provides programmable overcurrent and undercurrent detection. If a channel experiences an overload or undercurrent condition for longer than a programmable interval, that channel shuts down. Foldback current limiting keeps the internal MOSFET power dissipation at a safe level during overloads, and fast fault shutdown response ensures protection of both the system supply and the load. The MIC2596 automatically attempts to restart in response to overcurrent faults until the fault is cleared, while the MIC2597 latches the output off until reset by an external action. A logic-compatible signal is provided on each channel to indicate overcurrent or undercurrent fault conditions.

When a board is inserted into a live power system, high inrush currents are generated due to charging of bulk capacitors across the board's power pins. Although transient in nature, these inrush currents can be very large in magnitude. Such current spikes may cause the supply voltage to deviate from its regulated range, resulting in system crashes. In addition, high di/dt rates can cause permanent damage to electronic parts and/or components.

The MIC2596 family is designed to address these issues by limiting the inrush current that a PCB or other load can draw during a hot-swap event. In addition to inrush current control, the MIC2596/MIC2597 provide output current limiting and monitoring to ensure reliable protection of both the host system and the board.

In some systems, a significant ground potential difference may exist between the physical device monitor and the actual power control circuitry. For example, in a system spanning multiple equipment racks where a centralized CPU monitors hot-swap functions. To avoid the need for optoisolators or similar devices when using hot-swap components in such systems, the MIC2596/MIC2597 provide separate grounds for their on-chip power-related functions and digital interface pins (ON1, ON2, FAULT1#, FAULT2#). The unique architecture of these devices allows a ±8V potential difference between V_DDA ("analog" ground) and V_DDL ("logic" ground) without affecting device performance.

In distributed systems, V_DDA should be connected to the local return of the supply controlled by the MIC2596/MIC2597, while V_DDL should be connected separately to the ground of the monitoring and control logic. If tolerance of a voltage difference between V_DDA and V_DDL is not required, both grounds should be connected together at the device.

Referring to the typical application circuit, when a channel's ON pin is asserted, the corresponding MIC2596/MIC2597 output is enabled. To minimize inrush current transients, the output current is regulated to ensure it does not exceed the value programmed by resistor R1 (R2) connected to the I LIMIT pin.

The MIC2596 and MIC2597 act as electronic circuit breakers to protect loads, connectors, power supplies, and other system components from faults such as short circuits.

Features

• Safe hot swap in –48V systems
• Operating voltage up to –70V
• Programmable inrush current limiting
• Two thermally isolated channels
• Overcurrent fault detection and protection
• Anti-nuisance trip circuitry
• No-load detection
• Logic-compatible enable and fault signals
• Separate analog and logic ground pins support large system ground potential difference (±8V)

Applications

• Central office switching
• –48V power distribution