Electronic Components Datasheet Search |
|
SP3073E Datasheet(PDF) 1 Page - Exar Corporation |
|
SP3073E Datasheet(HTML) 1 Page - Exar Corporation |
1 / 6 page APPLICATION NOTE 1 AN207 ADVANTAGES OF ENHANCED RECEIVER FAILSAFE FEATURES IN RS-485/RS-422 SERIAL TRANSCEIVERS 1.0 INTRODUCTION RS-485/RS-422 receiver failsafe keeps the data bus in a known state when there are no active drivers on the bus. The Exar RS-485/RS-422 transceivers offer two different types of receiver failsafe: standard and enhanced. This application note will discuss how the enhanced receiver failsafe feature can help customers with failsafe problems while terminated. 2.0 STANDARD RECEIVER FAILSAFE RS-485/RS-422 devices such as Exar’s SP491 offer a standard receiver failsafe. The standard receiver failsafe feature for this device will provide a logic high at the receiver output when the receiver inputs are open circuit or floating. For example, when the data cable is disconnected, the receiver output will keep the line in a known high state. Standard receiver failsafe has an internal weak biasing network that will force the open inputs to >200mV thus resulting in a logic high output. Figure 1 shows the receiver configuration for failsafe logic high output. FIGURE 1. OPEN INPUT RECEIVER FAILSAFE Some applications operating at high speeds incorporate a termination resistor at the ends of the bus to prevent signal reflections. The termination resistor value should match the characteristic impedance of the data cable. In a majority of applications, the termination resistor is typically 120 ohms. When a termination resistor is connected between receiver inputs "A" and "B" the standard receiver failsafe feature will not operate properly (see Figure 2). FIGURE 2. TERMINATED RECEIVER INPUT |
Similar Part No. - SP3073E |
|
Similar Description - SP3073E |
|
|
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 |