Electronic Components Datasheet Search |
|
LTC4354IDDB Datasheet(PDF) 6 Page - Linear Technology |
|
LTC4354IDDB Datasheet(HTML) 6 Page - Linear Technology |
6 / 12 page LTC4354 6 4354f TI I G DIAGRA High availability systems often employ parallel-connected power supplies or battery feeds to achieve redundancy and enhance system reliability. ORing diodes have been a popular means of connecting these supplies at the point of load. The disadvantage of this approach is the significant forward voltage drop and resulting efficiency loss. This drop reduces the available supply voltage and dissipates significant power. A desirable circuit would behave like diodes but without the voltage drop and the resulting power dissipation. The LTC4354 is a negative voltage diode-OR controller that drives two external N-channel MOSFETs as pass transistors to replace ORing diodes. The MOSFETs are connected together at the source pins. The common source node is connected to the VSS pin which is the negative supply of the device. It is also connected to the positive inputs of the amplifiers that control the gates to regulate the voltage drop across the pass transistors. Using N-channel MOSFETs to replace Schottky diodes reduces the power dissipation and eliminates the need for costly heat sinks or large thermal layouts in high power applications. At power-up, the initial load current flows through the body diode of the MOSFET and returns to the supply with the lower terminal voltage. The associated gate pin will immediately start ramping up and turn on the MOSFET. The amplifier tries to regulate the voltage drop between the source and drain connections to 30mV. If the load current causes more than 30mV of drop, the gate rises to further enhance the MOSFET. Eventually the MOSFET gate is driven fully on and the voltage drop is equal to the RDS(ON) • ILOAD. When the power supply voltages are nearly equal, this regulation technique ensures that the load current is smoothly shared between them without oscillation. The current level flowing through each pass transistor de- pends on the RDS(ON) of the MOSFET and the output impedance of the supplies. In the case of supply failure, such as if the supply that is conducting most or all of the current is shorted to the return side, a large reverse current starts flowing through the MOSFET that is on, from any load capacitance and through the body diode of the other MOSFET, to the second supply. The LTC4354 detects this failure condition as soon as it appears and turns off the MOSFET in less than 1µs. This fast turn-off prevents the reverse current from ramping up to a damaging level. In the case where the pass transistor is fully on but the voltage drop across it exceeds the fault threshold, the FAULT pin goes high impedance. This allows an LED or optocoupler to turn on indicating that one or both of the pass transistors have failed. The LTC4354 is powered from system ground through a current limiting resistor. An internal shunt regulator that can sink up to 20mA clamps the VCC pin to 11V above VSS. A 1µF bypass capacitor across VCC and VSS pins filters supply transients and supplies AC current to the device. OPERATIO 4354 TD01 VDX – VSS VGATE tOFF 400mV 2V –100mV |
Similar Part No. - LTC4354IDDB |
|
Similar Description - LTC4354IDDB |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |