Electronic Components Datasheet Search |
|
LTC1685 Datasheet(PDF) 9 Page - Linear Technology |
|
LTC1685 Datasheet(HTML) 9 Page - Linear Technology |
9 / 12 page 9 LTC1685 Output Short-Circuit Protection The LTC1685 employs voltage sensing short-circuit pro- tection at the output terminals of both the driver and receiver. For a given input polarity, this circuitry deter- mines what the correct output level should be. If the output level is different from the expected, it shuts off the big output devices. For example, if the driver input is >2V, it expects the “A” output to be >3.25V and the “B” output to be <1.75V. If the “A” output is subsequently shorted to a voltage below VDD/2, this circuitry shuts off the big output devices and turns on a smaller device in its place (the converse applies for the “B” output). The outputs then appear as ±10mAcurrentsources.Notethatundernormal operation, the output drivers can sink/source >50mA. A time-out period of about 50ns is used in order to maintain normal high frequency operation, even under heavy ca- pacitive loads. If the cable is shorted at a large distance from the device outputs, it is possible for the short to go unnoticed at the driver outputs due to parasitic cable resistance. Addition- ally, when the cable is shorted, it no longer appears as an ideal transmission line, and the parasitic L’s and C’s might give rise to ringing and even oscillation. All these conditions disappear once the device comes out of short-circuit mode. For cables with the typical RS485 termination (no DC bias on the cable, such as Figure 10), the LTC1685 will auto- matically come out of short-circuit mode once the physical short has been removed. With cable terminations with a DC bias (such as Fast-20 and Fast-40 differential SCSI APPLICATIONS INFORMATION terminators, see Figure 15), the LTC1685 will not come out of short-circuit mode automatically upon release of the physical short. In order to resume normal operation, the DE pin has to be pulsed low for at least 200ns. High Speed Twisted Pair Transmission Data rates up to 52Mbps can be transmitted over 100ft of category 5 twisted pair. Figure 10 shows the LTC1685 receiving differential data from another LTC1685 trans- ceiver. Figure 11a shows a 26MHz (52Mbps) square wave propagated over 100ft of category 5 UTP. Figure 11b shows a more stringent case of propagating a single 20ns pulse over 100ft of category 5 UTP. Figure 12 shows a 4Mbps square wave over 1000ft of category 5 unshielded twisted pair. 1685 F11 DRIVER INPUT RECEIVER OUTPUT 10ns/DIV 2V/DIV 2V/DIV Figure 11a. 100ft of Category 5 UTP: 50Mbps 1685 F11b RECEIVER INPUT DRIVER INPUT RECEIVER OUTPUT 20ns/DIV 2V/DIV 5V/DIV 2V/DIV CABLE DELAY Figure 11b. 100ft of Category 5 UTP: 20ns Pulse Figure 10 100 Ω A 1 4 EN RO 1685 F10b 1/4 LTC1518 LTC1685 LTC1685 12 3 2 B 7 6 3 2 DE DI RO RE 4 1 100 Ω 7 6 3 2 DE DI RO RE 4 1 EN |
Similar Part No. - LTC1685 |
|
Similar Description - LTC1685 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |