QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 429 NEGATIVE 48V HOT SWAP CONTROLLER LT4250 DESCRIPTION Hot Swap is a trademark of Linear Technology Corpora- Demonstration circuit 429 is a Hot tion Swap controller designed for dual Feature Summary: 48V battery feeds in telecom subsys- OR-ing Diodes on 48V Inputs tems. This demo board is optimized for 2A maximum operating current, 5A Fuses making it ideal for loads of 25W to Independent Connection Sense Termi- 75W. The LT4250s circuit breaker is nal immune from transient currents aris- ing from load dump, voltage spikes, Optically Isolated Power Good Sig- and input steps. Provision is made naling for interfacing the LT4250s power On-Board Input and Output Clamps good output either directly or via an opto isolator to a power con- Table 1. Performance Summary verter, allowing for inclusion of a PARAMETER VALUE common mode filter block. The Connec- V range (survival) +100V to 100V IN tion Sense terminal helps eliminate uncontrolled arcing and associated Vin range (operating) 43V to 70V damage to the backplane connector in UVLO 38.5V off, 43V on real-world operating environments. OV 71V off, 70V on Design files for this circuit board Programmed inrush current 450mA are available. Call the LTC factory. (100F) QUICK START PROCEDURE DC429 is designed for either bench The other side of the edge connec- evaluation or direct testing by sub- tor or switch must connect to 48V stitution into an existing circuit RTN (terminal E1) in order to start board. The test setup is straightfor- the LT4250 Hot Swap controller. ward as shown in Figure 1 and 5. Connect Vout terminals E5 and E9 Figure 2. to the load or power converter mod- 1. Remove the fuses or OR-ing diodes ule input. from the existing circuit board. 6. Connect PWRGD terminal E6 to the 2. Connect 48V battery feeds to test power converter modules ENABLE terminals E3 and E4. pin. 3. Connect the battery feed returns to 7. If a series filter element of any terminal E1. description is present between DC429 and the module, use the opto 4. Attach terminal E2 Connection isolator terminals E7 and E8 to Sense to a short pin on the edge control the module. The opto tran- connector, or to a normally open sistor turns ON when power is GOOD. switch contact on the card ejector. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 429 NEGATIVE 48V HOT SWAP CONTROLLER 8. The board is ready for Hot Swap- Large wires may overwhelm the tur- ping. ret terminals. These terminals are not swaged and can be easily re- moved by desoldering. The holes are CONVERSION HINTS 0.095 inches in diameter, suitable To convert DC429 to an LT4250H, for wire sizes up to 12 AWG solid simply replace Hot Swap controller or stranded. U1 and use terminal E6, which will DC429 can be adapted for use at behave as a PWRGD (assert high) higher currents by resizing the output. Note that the opto isolator MOSFET, sense resistor, ORing di- is non-functional when the H ver- odes, and fuses. The minimum trace sion of the LT4250 is installed, width is 300mils, allowing for cur- and serves only as a pull-up. rents of up to 15A. (The boards are As supplied, PWRGD is pulled up by built with 1-ounce foil). R9 and the opto LED. To eliminate Do not attempt to measure the the opto isolator altogether, re- MOSFET gate voltage directly with a move R9 (30k ). Position R8 is pro- scope probe or a voltmeter. Measure vided in case a purely resistive instead the junction of R2 and R3, pull-up path is desired (see Sche- or at pin 6 (GATE of the LT4250). matic Diagram). CIRCUIT BOARD TO HOT SWAP 48V RTN (LONG) + CONNECTION SENSE (SHORT) NC DC/DC MODULE ON (ENABLE) 48V A (LONG) 48V B (LONG) REMOVE EXISTING FUSES OR OR-ING DIODES Figure 1. Setup for Circuit Board with no Input Filter 2