HV301

The Supertex HV301 and HV311 Hotswap Controllers provide control of power supply connection during insertion of cards or modules into live backplanes. They may be used in systems where active control is implemented in the negative lead of supplies ranging from ±10V to ±90V.

During initial power application the gate of the external pass device is clamped low to suppress contact bounce glitches by a "normally on" circuit which does not require initialization of the IC. Thereafter the UV/OV supervisors and power-on-reset work together to suppress gate turn on until mechanical bounce has ended. The HV301/311 then control the current inrush limit to a programmed level using one of two possible methods, i) servo control or ii) a drain to ramp capacitor. The above methods eliminate the need for extra hold-off or current limiting components. The devices also include an electronic circuit breaker, programmed by a sense resistor.

After the load capacitance has fully charged, the HV301/311 will transition into a low power mode, and enable the open drain PWRGD. In low power mode the HV301/311 continues to monitor the input voltage and monitor the current level. If a load fault occurs, the electronic circuit breaker will trip, the pass element will be turned off, and the PWRGD will return to an inactive state. Thereafter a programmable auto-retry timer will hold the device off to allow the pass element to cool before resetting and restarting. The auto-retry can be disabled using a single resistor if desired.

The HV301/HV311 includes a current mode servo-circuit which can be used as a return to limit during input voltage steps such as would be seen in a diode "ORed" situation when power switches back to regulated supply from battery operation. The HV301/HV311 allow independent programming of the trigger level of this phenomenon so that it may be set at a different level to the current limit level if desired. Under all circumstances the maximum servo period is limited to 100ms to protect the pass element.