DEMO CIRCUIT 537 QUICK STARTLTC4230 GUIDE LTC4230 Triple Hot Swap Controller with MultifuncDESCRIPTION Demonstration circuit DC537A is designed to evaluate the performance of the LTC4230 Triple Hot Swap Controller with multifunction current control. The board demonstrates all possible operation modes: power-up and power-down, when power rails turn on or turn off, steady state with constant load and overload conditions. The board contains one LTC4230 Controller, three power channels, three resistive feedback signal dividers, an ON pin circuit, and a circuit for configuration of the FAULT pin function. Each power channel includes a series connected power MOSFET and sense resistor. Design files for this circuit board are available. Call the LTC factory. LTC is a trademark of Linear Technology Corporation. PERFORMANCE SUMMARY PARAMETER Supply Voltage VCC1 Supply Voltage VCC2 Supply Voltage VCC3 Undervoltage Lockout, Channel 1 Undervoltage Lockout, Channel 2 Undervoltage Lockout, Channel 3 Circuit Breaker Trip Current GATEn Pin Pull-Up Slew Rate Normal Gate Pull-Down Slew Rate Fast Gate Pull-Down Slew Rate ON High Threshold Voltage ON Low Threshold Voltage FB Low Threshold Voltage FB Hysteresis Supply Voltage VCC1 Specifications are at TA = 25C CONDITIONS VCC2 VCC1 VCC3 (VCC1-1) VCC1 Low to High Transition VCC2 Low to High Transition VCC3 Low to High Transition Fast Comparator Slow Comparator Charge Pump On, 0 VGATE 0.2V ON Low, GATE=5V FAULT Latched and Circuit Breaker Tripped or in UVLO ON Low to High Transition ON High to Low Transition FB High to Low Transition VCC2 VCC1 VCC3 (VCC1-1) Supply Voltage VCC2 Supply Voltage VCC3 Undervoltage Lockout, Channel 1 Undervoltage Lockout VCC1 Low to High Transition VIN Rising, 0C < TA < 85C VIN Rising VIN Falling MIN 2.700 2.375 1.700 2.13 1.98 1.09 19.1 5.65 0.42 TYP MAX 16.5 16.5 16.5 2.52 2.32 1.29 23.8 8.65 1.13 UNITS 1.380 1.27 1.259 V V V mV 2.700 16.5 V 2.375 16.5 1.700 2.13 16.5 2.52 2.5 2.6 2.35 2.15 1.19 21.4 7.14 0.74 14.70 10.0 1.250 1.172 1.209 1.6 1.314 1.234 1.234 3 2.35 V V V V A V/ms V/ms V/s V V V V 1 LTC4230 OPERATING PRINCIPLES The LTC4230 is a triple hot swap controller that controls three supply voltages from 1.7V to 16.5V with VCC1 VCC2 VCC3. The LTC4230 is suited to low voltage power control in applications for hot board insertion or removal and electronic circuit breaker functions. The LTC4230 provides a rich set of features to support Hot Swap applications including: Under voltage lockout Programmable over voltage protection Programmable soft start with inrush current limiting Dual level over current fault protection Programmable over current response time Automatic retry or latched mode operation User-programmable supply voltage power-up rate Output voltages VOUTn monitoring and RESETn signaling Spurious RESETn signal elimination by the glitch filter Available in a 20 lead SSOP package, the LTC4230 is showcased on demonstration circuit DC537A configured for 1.7 to 16.5 volt operation with a slow comparator current limit protection in the range of 5.71A - 8.57A and a fast comparator - in the range of 19.3A - 23.6A. Pull-up resistors are provided to monitor the RESETn pin signals. MOSFET gate capacitors C7, C8, C9 define the output voltage slew rate. Initially the board is populated for nominal 0.74V/ms slew rate in each power channel. The external ON control signal should be higher than 2.8V. Three optional Zener diodes (D4, D5, and D6) can be used to protect the system against supply overvoltage condition on the load side of the pass transistor. QUICK START PROCEDURE Demonstration circuit 537 is easy to set up to evaluate the performance of the LTC4230. Refer to Figure 1 for proper board connections with power supplies, loads, and the ON control signal source. Demonstration Circuit 537 has three optional components R13, R10, and R7 for the output voltage monitoring value adjustments and one user configurable jumper JP1 option. Calculate R13, R10, and R7 resistors based at the selected channel voltages and install them on the board. Place jumper J1 in the AUTORETRY position to evaluate automatic retry when current limit is reached, or in the STATUS position to evaluate latched mode operation. 2 With power off, connect three power supplies capable of supplying 25A to the appropriate V1_IN, V2_IN, V3_IN turrets and GND. Supplies voltages should satisfy the conditions shown in the PERFORMANCE SUMMARY and VCC1*VCC2; VCC3*(VCC1-1). Connect the ON pin to a signal source capable of developing 16V>VON>1.39V to the turret labeled ON/OFF and be sure that the ON signal is initially zero (low). NO LOAD TEST Turn on the power supplies, verify the input voltages, and then switch the ON control signal from low to high ( 1.39V). All three outputs should come up. LTC4230 Verify the RESETn turret signals. All three voltages should be lower than 0.5V. Switch the ON control signal from high to low. All outputs should go down. RATED LOAD TEST Repeat the test with resistive loads connected to each output. Be sure that the current in each channel does not exceed 5.65A current limit. OVER CURRENT FAULT TEST Three separate tests are needed to verify the circuit breaker functions. First two tests run with conditions for slow comparator operation; third test - for fast comparator operation. Monitor the turn off events with a digital storage scope. 1. With the outputs unloaded and the circuit functioning, connect a load to the selected channel output, which will draw 10A current. The channel will fault. Verify latch off and automatic retry modes by changing the jumper JP1 position. Repeat this test for each channel. 2. With the jumper JP1 in the STATUS position, the board unpowered and the ON control signal high, connect a load capable of drawing 10A to any channel output. Leave the other two channels unloaded. First, turn the two unloaded channel supplies on. Then turn on the third supply and verify that LTC4230 is in the latch mode. NOTE. This test can be run only with the components initially installed on the board and the channel operating voltage VCCn*12V. Otherwise, the MOSFET can operate out of the safe operating area, and not survive. Higher operating voltages or higher currents require a larger FET. 3. Adjust the resistive load to draw 24A current in channel 1 to demonstrate the FAST comparator fault.. With the jumper JP1 in the STATUS position, the unloaded outputs and the circuit functioning, connect this load to the channel 1 output. Verify that LTC4230 is in the latch mode. UNDER VOLTAGE LOCKOUT TEST Test under voltage lockout functionality by reducing the input voltage below 2.15V for channel 1, below 1.98V for channel 2, and below 1.09V for channel 3. CHANNEL SEQUENCING If power on sequencing is desired, remove the RESETn pin pull-ups. Choose the channel sequence in the power up mode. Connect the RESETn1 pin to the GATEn2 pin; connect RESETn2 pin to the GATEn3 pin. The additional indexes 1, 2, 3 show channel sequencing order. As FBn1 pin exceeds its threshold RESETn1 will release the MOSFET GATEn2 pin; as the FBn2 pin exceeds its threshold, RESETn2 will release the channel MOSFET GATEn3 pin. Apply ON signal and observe the start up sequencing. 3 LTC4230 4 LTC4230 5