DEMO CIRCUIT 1364 QUICK START GUIDE LTC4224 LTC4224 Compact Dual Low Voltage Hot Swap Controller DESCRIPTION designs, with a dual SO-8 FET on the back side of the board. Demonstration circuit DC1364 features the LTC4224 Compact Dual Low Voltage Hot Swap Controller. Design files for this circuit board are available. Call DC1364 facilitates evaluation of the LTC4224 perform- the LTC factory. ance characteristics including supply ramp-up transients, steady state, and overcurrent fault conditions. Onboard L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy LEDs indicate input supply presence, output supply, and Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode fault conditions. Layout is optimized for narrow pitch Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelPro- SENSE tect, PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. PERFORMANCE SUMMARY Specifications are at TA = 25C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V V Supply Voltage Range V = Max (V , V ) 2.7 6.0 V CC CC CC CC1 CC2 V V Undervoltage Lockout V Rising 2.2 2.37 2.65 V CC(UVL) CC ICC V V Supply Range V = Min (V , V ), V 2.7V 1.0 6.0 V CCLO CCLO CCLO CC1 CC2 CC V Undervoltage Lockout V Falling 0.76 0.8 0.84 V CCLO(UVL) CCLO V Gate Drive (V -V ) I =0A, -1A 4.5 5.5 7 V GATE GATEn CC GATEn V Circuit Breaker Trip Sense Voltage (V V ) V = 3.6V 22.5 25 27.5 mV SENSE(CB) IN OUT IN (V SENSEn ) CCn V ONn Threshold Voltage V Rising 0.76 0.8 0.84 V ON(TH) ONn V 15 30 50 mV ON(HYST) I ONn Pull-Up Current V =0.6V 5 10 15 A ON(IN) ON OPERATING PRINCIPLES The LTC4224 controls two rails with external N-channel no need for additional timing components. A fast-acting MOSFETs. Either supply rail operates as low as 1V, pro- current limiting amplifier and timed circuit breaker pro- vided the other supply is 2.7V or greater. The maximum tect the load and power MOSFETs from excessive power operating voltage is 6.0V for both channels. The dissipation in overcurrent conditions. LTC4224 can ramp up supplies in any order, and the out- The supply rails turn on and off independently under put voltage slew rate is adjustable with external gate ca- control of the ON1 and ON2 inputs. Each ON input is pacitors. All timing delays are generated internally, with pulled high by internal 10A current source. 1 LTC4224 The gate voltage comes up when one of the two rail volt- The LTC4224-1 latches off after a current fault, while the ages exceeds the 2.4V undervoltage lock out level for LTC4224-2 automatically restarts following a cool down 160ms and the associated ON control signal drop to less delay. than 0.8V. The gate driver is a 10uA current source that DC1634 is designed for operation with +5V, 1A rail ramps the gate voltage to 5.5V above the rail voltage. (channel 1) and +3.3V, 2A rail (channel 2). The Active Current Limiting (ACL) amplifier controls gate voltage to regulate 25mV across the sense resistor QUICK START PROCEDURE Demonstration circuit DC1364 is easy to set up to evalu- 4. Connect voltmeters to the FAULT, VOUT1, and ate the performance of the LTC4224. Refer to Figure 1 VOUT2 turrets. Turn on the +5.0V and +3.3V sup- for proper measurement equipment setup and follow the plies. Two green LEDs VIN1 and VIN2 should light. procedure below: 5. Turn on the +5.0V rail by placing JP2 (ON1) to the 1. Place jumpers in the following positions: ON position. Green LED D3 (VOUT1) should light JP1 VIN1 6. Turn on the +3.3V rail by placing JP3 (ON2) to the ON position. Green LED D4 (VOUT2) should light. JP2 OFF 7. Turn on electronic loads and verify circuit breaker JP3 OFF thresholds: (1.46-1.85) A for the +5.0V rail and 2. With the power off, connect the +5.0V and +3.3V (2.23-2.80) A for the +3.3V rail. power supplies to the VIN1, VIN2 and GND turrets. 8. The red FAULT led (D5) indicates an overcurrent 3. Connect VOUT1, VOUT2 and GND turrets to ap- fault on either rail. Toggling the ON signal to the propriate (+5.0V, 3A and +3.3V, 5.0A) disabled faulted rail clears the fault. electronic loads or passive resistive loads (2.7 9. Verify supply ramp up using a capacitive load on Ohms and 1.0 Ohms.) the +5.0V rail. A 1200uF load should power up properly, while a 2200uF load should cause a fault. 2