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LTC4300-1 Datasheet(PDF) 11 Page - Linear Technology |
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LTC4300-1 Datasheet(HTML) 11 Page - Linear Technology |
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11 / 18 page  LTC4300-1/LTC4300-2 11 430012fb For more information www.linear.com/LTC4300-1 associated with hot swapping have settled. Owing to their small capacitance, the SDAIN and SCLIN pins cause minimal disturbance on the backplane busses when they make contact with the connector. Figure 6 shows the LTC4300-2 in a CompactPCI con- figuration. The LTC4300-2 receives its VCC voltage from one of the long “early power” pins. Because this power is not switched, add a 5Ω to 10Ω resistor between the VCC pins of the connector and the LTC4300-2, as shown in the figure. In addition, make sure that the VCC bypass- ing on the backplane is large compared to the 0.01µF bypass capacitor on the card. Establishing early power VCC ensures that the 1V precharge voltage is present at the SDAIN and SCLIN pins before they make contact. Connect VCC2 to the output of one of the CompactPCI power supply Hot Swap circuits. VCC2 is monitored by a filtered UVLO circuit. With the VCC2 voltage powering up after all other pins have established connection, the UVLO circuit ensures that the backplane and card data and clock busses are not connected until the transients associated with hot swapping have settled. Figure 7 shows the LTC4300-1 in a PCI application, where all of the pins have the same length. In this case, connect an RC series circuit on the I/O card between VCC and ENABLE.AnRCproductof10msprovidesafiltertoprevent theLTC4300-1frombecomingactivateduntilthetransients associated with hot swapping have settled. Figure 8 shows the LTC4300-2 in an application where the user has a custom connector with pins of three different lengths available. Making VCC2 the shortest pin ensures that all other pins are firmly connected before VCC2 receives any voltage. A filtered UVLO circuit on VCC2 ensures that the VCC2 pin is firmly connected before the LTC4300-2 connects the backplane to the card. Repeater/Bus Extender Application Users who wish to connect two 2-wire systems separated by a distance can do so by connecting two LTC4300-1s back-to-back, as shown in Figure 9. The I2C specification allows for 400pF maximum bus capacitance, severely limiting the length of the bus. The SMBus specification places no restriction on bus capacitance, but the limited impedances of devices connected to the bus require sys- tems to remain small if rise and fall time specifications are to be met. The strong pull-up and pull-down imped- ances of the LTC4300-1 are capable of meeting rise and fall time specifications for one nanofarad of capacitance, thus allowing much more interconnect distance. In this situation, the differential ground voltage between the two systems may limit the allowed distance, because a valid logic LOW voltage with respect to the ground at one end of the system may violate the allowed VOL specification with respect to the ground at the other end. In addition, the connection circuitry offset voltages of the back-to- back LTC4300-1s add together, directly contributing to the same problem. Systems with Disparate Supply Voltages (LTC4300-1) In large 2-wire systems, the VCC voltages seen by devices at various points in the system can differ by a few hun- dred millivolts or more. This situation is well modelled by a series resistor in the VCC line, as shown in Figure 10. For proper operation of the LTC4300-1, make sure that VCC(BUS) ≥ VCC(LTC4300) – 0.5V. 5V to 3.3V Level Translator and Power Supply Redundancy (LTC4300-2) Systems requiring different supply voltages for the back- plane side and the card side can use the LTC4300-2, as shown in Figure 11. The pull-up resistors on the card side connect from SDAOUT to SCLOUT to VCC2, and those on the backplane side connect from SDAIN and SCLIN to VCC. The LTC4300-2 functions for voltages ranging from 2.7V to 5.5V on both VCC and VCC2. There is no constraint on the voltage magnitudes of VCC and VCC2 with respect to each other. This application also provides power supply redundancy. If either the VCC or VCC2 voltage falls below its UVLO threshold, the LTC4300-2 disconnects the backplane from the card, so that the side that is still powered can continue to function. applicaTions inFormaTion |
Similar Part No. - LTC4300-1_15 |
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Similar Description - LTC4300-1_15 |
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