DEMO MANUAL DC1354B LT1641-1, LT1641-2, LT4256-1, and LT4256-2 Positive High Voltage Hot Swap Controller DESCRIPTION Demonstration circuit 1354B is a positive high voltage hot The LT1641-1 and LT4256-1 latch off if MOSFET shuts swap controller featuring either the LT 1641-1, LT1641-2, off under overcurrent condition, while LT1641-2 and LT4256-1, or LT4256-2. LT4256-2 automatically restart after time-out delay. The board facilitates measurement of transient conditions, The DC1354B contains one hot swap controller, power steady state operation with different loads, and fault con- MOSFET, current sense resistor, enable circuit, input volt- ditions. The Controller responds to fault conditions such age clamp, gate protection circuit, resistive output voltage as input undervoltage(UV), output power good (PWRGD) divider for feedback signal, and three LEDs to indicate the fault, and overcurrent and response can be verified by the presence of input and output voltages and power good output voltage (V ) LED state and PWRGD pin signal. condition. OUT All registered trademarks and trademarks are the property of their respective owners. Design files for this circuit board are available. Specifications are at T = 25C PERFORMANCE SUMMARY A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Operating Voltage LT1641 9 80 V CC LT4256 10.8 80 V V V Undervoltage Lockout LT1641 7.5 8.3 8.8 V LKO CC LT4256 9.8 V V Undervoltage Threshold LT1641, ON pin voltage Low to High transition 1.28 1.313 1.345 V UNLH LT4256, UV pin voltage Low to High transition 3.96 4 4.04 V V Feedback Voltage Threshold LT1641, FB Low-to-High Transition, 1.28 1.313 1.345 V FB FB High-to-Low Transition 1.221 1.233 1.245 V LT4256, FB Low-to-High Transition, 3.95 3.99 4.03 V FB High-to-Low Transition 4.2 4.45 4.65 V V SENSE Pin Trip-Voltage(V -V ) LT1641, V =0V 8 12 17 mV SENSETRIP CC SENSE FB V =1V 39 47 55 mV FB LT4256, V =0V 5.5 14 22 mV FB V 2V 45 55 65 mV FB V External N-Channel Gate Drive LT1641, V - V , 10.8V V 20V 4.5 18 V GATE GATE CC CC 20 VV 80V 10 18 V CC LT4256, V - V , 10.8V 20V 4.5 8.8 12.5 V GATE CC CC 20 VV 80V 10 11.6 12.8 V CC I GATE Pin Pull-Up Current LT1641 5 10 20 A GATEUP LT4256 16 32 63 A I GATE Pin Pull-Down Current LT1641 35 70 100 mA GATEDN LT4256 40 62 80 mA Rev 0 1DEMO MANUAL DC1354B OPERATING PRINCIPLES The LT1641-1, LT1641-2, LT4256-1, and LT4256-2 are voltage by replacing the enable circuit (R5, R11), input positive high voltage hot swap controllers that have abso- voltage clamp (D1), gate protection circuit (R8, R14, D3, lute maximum supply voltage (V ) 100V and operating D6), and resistive output voltage divider (R10, R12). The CC range (9-80) V for LT1641 and (10.8-80) V for LT4256. DC1354B as supplied by the factory is assembled with In the DC1354B, any controller operates on the +48V the SUM90N10-8m2p MOSFET in a D2PAK package and rail. Each board can easily be readjusted for any rated 7m current sense resistor (R1). QUICK START PROCEDURE Demonstration circuit DC1354B is easy to set up to evalu- 2. Place a scope probe to the VOUT turret, turn on con- ate the performance of the LT1641-1, LT1641-2, LT4256- troller, and measure a power-up time with no load. For 1, and LT4256-2. Refer to Figure1 for proper measure- LT4256 this time must be in the range (13.7 - 54) ms, ment equipment setup and follow the procedure below. and for LT1641- (43 - 173) ms. The board test is performed in several steps by measur- 3. Connect Low Capacitive Load to the output of hot swap ing some transient parameters and verifying successful circuitry (VOUT +48V turret). Turn on controller. This or failed power up actions under defined conditions. In power up should be successful and two LEDs (V OUT all test steps turn on switch SW PS to connect demo green and PWRGD - green) must light. board to the +48V power supply, turn on switch SW PS to NOTE. The following tests verify loaded controller perfor- activate controller (connecting the ENABLE pin to the VIN mance. The transients with Low Load should be success- +48V) and turn +48V off for resetting controller after fault. fully completed, while transients with High Load should 1. It should be noted that loading parameters such as Low fail. The LT1641-1 and LT4256-1 in the overcurrent Capacitive Load, High Capacitive Load, Low Resistive fault condition are latched off, while the LT1641-2 and Load, and High Resistive are different for LT4256 and LT4256-2 provide retry. To avoid power MOSFET dam- for LT1641. These parameters are shown below sepa- age in the LT1641-2 and LT4256-2 High Load tests keep rately for each controller: switch SW ON in the on position for a very short time. LT1641 4. Connect High Capacitive Load to the output of hot swap circuitry (VOUT +48V turret). Turn on controller. This n Low Capacitive Load: 1000uF power up should be unsuccessful, and the two LEDs n High Capacitive Load: 8700uF remaining off will confirm this. n Low Resistive Load: 10, 50W For LT4256-1 and LT1641-1, the failed power-up is indi- cated by the VOUT (green) and PWRGD (green) LED lights n High Resistive Load: 5.5 remaining off. Disconnect the ENABLE turret from the LT4256 VIN +48V turret for short time and connect them again. n The controller should be latched off in the shut off mode. Low Capacitive Load: 250uF n For LT4256-2 and LT1641-2, make short time connection High Capacitive Load: 3500uF of the ENABLE turret and VIN +48V. The V (green) and OUT n Low Resistive Load: 11, 50W PWRGD (green) LED will blink indicating an autoretry in n High Resistive Load: 5.0 the failed power up. Rev 0 2