Electronic Components Datasheet Search |
|
UM3352E Datasheet(PDF) 8 Page - Union Semiconductor, Inc. |
|
UM3352E Datasheet(HTML) 8 Page - Union Semiconductor, Inc. |
8 / 11 page ________________________________________________________________________ http://www.union-ic.com Rev.02Jun.2013 8/11 UM3352E Applications Information 256 Transceivers on the Bus The standard RS-485 receiver input impedance is 12kΩ (one unit load), and the standard driver can drive up to 32 unit loads. The Union family of transceivers have a 1/8 unit load receiver input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on one communication line. Any combination of these devices and/or other RS-485 transceivers with a total of 32 unit loads or less can be connected to the line. Reduced EMI and Reflections The UM3352E is slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. In general, a transmitter’s rise time relates directly to the length of an unterminated stub, which can be driven with only minor waveform reflections. The following equation expresses this relationship conservatively: Length=tRISE/(10×1.5ns/ft) Where tRISE is the transmitter’s rise time. A system can work well with longer unterminated stubs, even with severe reflections, if the waveform settles out before the UART samples them. Low-Power Shutdown Mode Low-power shutdown mode is initiated by bringing both RE ______ high and DE low. In shutdown, the device typically draws only 2nA of supply current. RE ______ and DE may be driven simultaneously; the parts are guaranteed not to enter shutdown if RE ______ is high and DE is low for less than 50ns. If the inputs are in this state for at least 600ns, the parts are guaranteed to enter shutdown. Enable times tZH and tZL in the Switching Characteristics tables assume the part was not in a low-power shutdown state. Enable times tZH(SHDN) and tZL(SHDN) assume the parts were shut down. It takes drivers and receivers longer to become enabled from low-power shutdown mode (tZH(SHDN), tZL(SHDN)) than from driver/receiver-disable mode (tZH, tZL). Driver Output Protection Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus contention. The first, a foldback current limit on the output stage, provides immediate protection against short circuits over the whole common-mode voltage range. The second, a thermal shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature becomes excessive. Line Length vs. Data Rate The RS-485/RS-422 standard covers line lengths up to 4000 feet. For line lengths greater than 4000 feet, repeater is required. Typical Applications The UM3352E transceivers are designed for bidirectional data communications on multipoint bus transmission lines. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. |
Similar Part No. - UM3352E |
|
Similar Description - UM3352E |
|
|
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 |