Power MOSFET & current sensing are integrated in 20A hot-swap controller

April 28, 2015 // By Graham Prophet
LTC4234 is a 20A Hot Swap controller with integrated MOSFET and current sensing, providing a small footprint hot-plug solution for high density circuit boards.

The device ensures safe board insertion and removal from live 2.9V to 15V backplanes by controlling an internal N-channel power MOSFET to gently power up bulk capacitors, avoiding sparks, connector damage and system glitches. By integrating the two most critical and largest Hot Swap components – the power MOSFET and sense resistor – the LTC4234 reduces design time and saves board area. The internal MOSFET’s safe operating area (SOA) is production tested and specified to ensure a rugged hot-plug solution, especially for space-constrained boards and cards in servers, network routers and switches, solid state drives and industrial systems.

Upon insertion, the LTC4234 waits for connector contact bounce to finish before soft-starting the output. A ground-referenced signal proportional to the load current is provided for monitoring with an external analogue-to-digital converter (ADC). The current limit can be reduced from its 22.5A default with a single resistor, affording quick adjustment for dynamic load changes and various applications. For higher current applications, two LTC4234s can be paralleled for a 40A solution. During overcurrent conditions, the controller limits MOSFET power dissipation by folding back its current limit for an adjustable timeout period. Undervoltage and overvoltage thresholds protect downstream loads against voltages outside a valid window, preventing circuit malfunction and damage.

Specified over the 0°C to 70°C commercial, -40°C to 85°C industrial and -40°C to 125°C automotive temperature ranges, the LTC4234 is housed in a 38-pin 5 x 9 mm QFN package, for $4.95 (1000).

Linear Technology; www.linear.com/product/LTC4234

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