DEMO MANUAL DC1627A LTC4226 Wide Operating Range Dual Hot Swap Controller Description Demonstration circuit 1627A is intended to display the Both channels of this circuit operate with a 1.25A maximum Hot Swap functionality of the LTC 4226 wide operating current in the 12V rails. It is not recommended to use this range dual Hot Swap controller. The DC1627A has two circuit for other operating conditions. independent circuits, each for two rails. The circuit placed There are two versions of the controller: LTC4226-1 and on the upper board area is for a high current load. LTC4226-2. The LTC4226-1 remains off after a fault while The first channel of the upper board circuit operates with the LTC4226-2 automatically retries after a 0.5 second a 10A maximum in the +12V rail while the second channel delay. operates with a 5A maximum in the +5V rail. Provision is The DC1627A allows estimating the performance of the made for the installation of several MOSFET packages to LTC4226 in different operation modes such as ramp-up, test the LTC4226 s performance during a short time with steady-state, and overcurrent fault conditions. the larger current. Circuit LEDs indicate a presence of the Design files for this circuit board are available at input rail voltages and fault conditions in each rail. There are DEMO MANUAL DC1627A p s Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Circuit Breaker Current Limit 4.45 5 5.55 A CB2 t Timer Period During Circuit Breaker Operation 39 50 80 ms CB2 I Current Limit by CL Amplifier CLS = 0V (1.5) 6.9 8.6 10.4 A LIM2 CLS = Open (2) 9.2 11.5 13.7 A CLS = 3V (3) 13.8 17.3 20.7 A t Fault Timer Period CLS = 0V (1.5) 3.3 5.1 8.4 ms FTMR2 CLS = Open (2) 1.9 2.8 4.7 ms CLS = 3V (3) 0.8 1.3 2.1 ms Compact Circuit for FireWire Power Distribution V Input Supply Range Based on the ON Pin Threshold 4.62 16.7 V CC V Input Supply Undervoltage V Rising 4.62 4.96 5.28 V CC(UV) CC I Circuit Breaker Current Limit 1.35 1.51 1.68 A CB t Timer Period During Circuit Breaker Operation 6.07 9.2 15.3 ms CB I Current Limit by CL Amplifier CLS = 0V (1.5) 2.1 2.6 3.2 A LIM CLS = Open (2) 2.8 3.5 4.2 A CLS = 3V (3) 4.2 5.3 6.3 A t Fault Timer Period 0.6 0.9 1.6 ms CLS = 0V (1.5) FTMR 0.35 0.5 0.9 ms CLS = Open (2) 0.15 0.25 0.39 ms CLS = 3V (3) o p The LTC4226 controls two rails with external N-channel active current limiting. By this means, the timer period MOSFETs. Two independent ONn comparators allow ramp- during an active current limit is ten times less than it is in ing rails up and down independently. the circuit breaker operation. During normal operation, the charge pump delivers 9A to The LTC4226-1 latches off after the MOSFET is turned off the gate driver to turn on the external N-channel MOSFET. under an overcurrent condition. The ON pin status must be recycled low to high for the gate drive to restart. The Each channels circuit breaker (CB) comparator and cur- demo board with LTC4226-1 is labeled as DC1627A-A. rent limit (CL) amplifier monitor the load current using the sense resistor voltage between the V and the SENSEn The LTC4226-2 automatically retries after an overcurrent CCn pins. When the sense resistor voltage exceeds circuit condition. It begins with a 0.5 second delay before resetting breaker threshold (V ), (but lower than V ) the CB the fault timer with a 100A pull-down, followed by gate CB LIMIT comparator enables a 2A current source, and the voltage restart if ON pin is high. The demo board with LTC4226-2 at the fault timer (FTMRn) capacitor ramps up. When the is labeled as DC1627A-B. FTMRn comparator voltage reaches 1.23V threshold, the Both channels share a common current limit select func- corresponding MOSFET is turned off. tionality with the current limit select (CLS) pin signal. This When the sense resistor voltage exceeds V , the CL signal can have three input states: low, open and high. The LIMIT amplifier limits the current in the load by reducing the three input states correspond to the preset current limit gate-to-out voltage in an active control loop. The fast values. V becomes 1.5, or 2.0, or 3.0 of 1.15 V . LIMIT CB response CL amplifier can quickly adjust the gate-to-out Undervoltage protection in the upper circuit is based on the voltage in the event of an output-to-ground short circuit. ONn pin threshold. The resistors of each ONn pin divider The FTMRn capacitor voltage ramps up with a 20A (or are selected to have a threshold voltage at the LTC4226 ON 36A, or 80A) current source instead of the 2A in the dc1627af 2 rinciples perating ummary erformance