4µA IQ hot swap controller protects batteries

August 26, 2014 // By Graham Prophet
LTC4231 is an ultra-low quiescent current (IQ) Hot Swap controller, enabling safe board or battery insertion and extraction from 2.7V to 36V systems.

The LTC4231 controls an external N-channel MOSFET to 'gently' power up board capacitors, avoiding sparks, connector damage and system glitches. Device quiescent current is 4 µA during normal operation, dropping to 0.3 µA in shutdown mode. To ensure low current operation, the undervoltage and overvoltage resistive dividers are connected to a strobed ground, lowering their average current draw by 50x. The LTC4231 provides a compact and rugged micropower solution for hot plugging and battery protection, especially in energy conscious applications using solar power or energy harvesting. Current limit acts in under 1 µsec, and there is selectable latch-off or auto-retry after a current fault.

The chip survives and also protects downstream circuitry from reversed batteries up to -40V by controlling back-to-back N-channel MOSFETs. Undervoltage protection cuts off low voltage batteries to prevent deep discharge, while adjustable hysteresis avoids oscillations from battery recovery after load removal. Dual level overcurrent protection is provided by a timed circuit breaker and fast current limit. The 2.7V to 36V operating range accommodates a wide range of battery chemistries including lead-acid, Li-Ion and stacked NiCd.

The LTC4231 is available in two options: the LTC4231-1 remains off after an overcurrent fault, whereas the LTC4231-2 automatically attempts to turn on after a 500 msec cool-down period. Specified over the 0°C to 70°C commercial and -40°C to 85°C industrial temperature ranges, the LTC4231 is in 12-pin MSOP and 3 x 3 mm QFN packages from $2.25 (1000).

Linear Technology; www.linear.com/product/LTC4231