DC684A Analog Devices

DEMO MANUAL DC684A LT4256-3 48V Hot Swap Controller Description Demonstration circuit 684A is a 48V Hot Swap controller Selectable Auto Retry or Latchoff on Overcurrent Faults featuring the LT4256-3 in a 2A application. The LT4256-3 Power Good Monitor is ideally suited for demanding power distribution control Open MOSFET Detection in 12V, 24V and 48V applications for hot board insertion protection, high side power switching, and electronic Available in a 16-lead SSOP package, the LT4256-3 is circuit breaker functions. The LT4256-3 provides a rich showcased on demonstration circuit 684A configured for set of features to support Hot Swap applications including: a 48V, 2A application. By changing a few passive compo- nents, 12V and 24V applications can easily be evaluated Overvoltage Shutdown at up to 10A provided the thermal considerations of pass Undervoltage Lockout FET Q1 are taken into account. Foldback Inrush Current Limiting Design files for this circuit board are available at Overcurrent Circuit Breaker with Programmable DEMO MANUAL DC684A Quick s Dp Demonstration circuit 684A is easy to set up to evaluate to the turret Vmicro to monitor the OPEN pin on the turret the performance of the LT4256-3. Refer to Figure 1 for labeled OPEN proper measurement equipment setup and follow the NOTE: The OPEN and PWRGD pins are provided with procedure below: separate supplies to facilitate connection of the PWRGD Demonstration circuit 684A has two user configurable to a DC/DC power converter which may require a different jumper options: voltage than the system processor which would monitor the OPEN state. J1 Retry: Set to ON for auto retry or OFF for latchoff on overcurrent faults. Connect a suitable load to the VOUT and GND turrets. This load can be an electronic load or power resistors (24W at J2 LED Function: Select PWRGD or VOUT PRESENT. 100W for 2A at 48V) can be used. In the former position, LED D6 will only illuminate when the output voltage crosses the 44.9V threshold. NOTE: Because the LT4256 incorporates foldback current In the latter position, D6 will illuminate whenever Q1 limiting, the nominal startup current supplied to the load is enhanced. is 700mA and can be as low as 500mA. This current limit increases linearly until the FB pin exceeds 2V (VOUT > With power off, connect a nominal 48V power supply 20V). An electronic constant current load set to 2A will capable of supplying 3A to the VIN and GND turrets. not permit the circuit to turn on unless it is gated on by Connect a logic level supply to the turrets labeled VLOGIC the PWRGD signal (as would be the case with a DC/DC and GND to monitor the PWRGD state on the turret la- converter controlled by the PWRGD signal). Resistive beled PWRGD. This same supply can also be connected loading will not have this problem. + + + + + V LOAD IN + + VOUT OR SYSTEM PWRGD SUPPLY V V OPEN PWRGD + V MICRO Figure 1. Proper Measurement Equipment Setup dc684af 2 ure roce tart