DEMO MANUAL DC1741B LTC4370 Two-Supply Diode-OR Current Balancing Controller DESCRIPTION Demonstration circuit DC1741B features the LTC 4370, when the MOSFETs are disabled. The LTC4370 provides a a two supply diode-OR current sharing controller in a rich set of features to support shared current diode-ORed typical 2.9V to 18V, 16A sharing application. applications including: The maximum MOSFET voltage drop V = V OUT Load Sharing Between Two Supplies FR IN is set with an external resistor, up to 600mV. A fast gate Elimination of the Need for Active Control of Input turn-on reduces the load voltage droop during supply Supplies switchover. If the input supply fails or is shorted, a fast Elimination ofShare Bus turn-off minimizes the transient reverse current. Reverse Current Blocking Disabling the load sharing function turns the LTC4370 into a dual ideal diode controller. Elimination of Shoot-Through Current During Start-Up or Faults Two enable input pins, EN1 and EN2, allow enabling and disabling each rails MOSFET individually while the Design files for this circuit board are available. MOSFETs inherent diodes create diode-OR connection All registered trademarks and trademarks are the property of their respective owners. PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V V and V Input Voltage Operating 2.9 18 V IN IN1 IN2 Range With External V Supply 0 V CC CC V V External Supply Operating Range V , V V 2.9 6.0 V CC(EXT) CC IN1 IN2 CC V V Regulated Voltage 4.5 5 5.5 V CC(REG) CC V Error Amplifier Input Offset 0 2 mV EA(OS) g Error Amplifier Gain 150 S m(EA) V Forward Regulation Voltage (V V ) V =1.2V, V = 5V 2 12 25 mV FR IN OUT IN CC V =12V 2 25 50 mV IN V MOSFET Gate Drive (GATEV ) V = 0.2V I = 0, 1A Highest V = 12V 10 12 14 V GATE IN FWD IN V = 0.2V I = 0, 1A Highest V = 2.9V 4.5 7 9 V FWD IN I GATE1, GATE2 Fast Pull-Up Current V = 0.4V, V = 0V, CPO = 17V 0.9 1.4 1.9 A GATE FWD GATE GATE1, GATE2 Fast Down-Up Current V = 2V, V = 5V, 0.9 1.4 1.9 A FWD GATE GATE1, GATE2 Off Pull-Down Current Corresponding EN =1V, V = 2.5V 65 110 160 A GATE V EN1, EN2 Threshold Voltage EN Falling 580 600 620 mV EN(TH) V MOSFET On-Detect Threshold FETON Transitions High 0.28 0.7 1.1 V GATE(ON) (GATEV ) IN I Maximum Continuous Load Current Sharing active, limited by SUM90N04-3m3P-E3 Dissipation 16.6 A OUT Rev. A 1DEMO MANUAL DC1741B OPERATING PRINCIPLES The LTC4370 controls N-channel MOSFETs, M1 and M2, Two LEDs, OFF1 and OFF2, indicate the MOSFETs status. to share the load between two input rails.The error ampli- Each LED lights up when the gate voltage is less than fier compares OUT1 and OUT2, and controls servo ampli- 0.7V above V . IN fiers which regulate the MOSFET forward voltage drop Pay special attention to the power supply features used to V . Combined action of the error amplifier and servo FR with the LTC4370. amplifiers forces OUT1 and OUT2 to be equal and as a This controller may not work properly with supplies utiliz- result the rail currents are equal. The board RANGE resis- ing synchronized rectification in the output stage unless tor R3 = 30.1k defines the maximum regulation voltage the internal circuit of the supply has the ability to limit range as 265mV to 375mV. negative current or to block it completely. Exercise caution The board is assembled with SUM90N04-3m3P-E3 when using the controller with this type of supply unless N-channel MOSFETs, which in a single channel applica- it is determined that it contains the required circuitry. tion has current capability up to 20A. In the load share mode, the installed components guarantee continuous proper load sharing up to 16.6A total load. For a short test time of 3 to 5 seconds, it is possible to double this load. Rev. A 2