BL3085B www.belling.com.cn v1.2 page- 1 - high esd-protected, fail-safe, slew-rate-limited rs-485 transceivers general description the BL3085B is a half-duplex rs-485 transceiver wit h 18kv iec 61000-4-2 contact discharge protection. the BL3085B contains one driver and one receiver. the device features fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted. this means that the receiver output will be logic high even if all transmitters on a terminated bus are disabled. the BL3085B features reduced slew-rate driver that mini mizes emi and reduces reflections caused by improperly terminated cables, allowing error-free d ata transmission up to 250kbps. the BL3085B has a 1/8 unit load receiver input impedance that allows up to 256 transceivers on the bus. configuration functional block of BL3085B applications rs-485 communications level translators transceivers for emi-sensitive applications industrial control local area networks energy meter networks lighting systems
BL3085B www.belling.com.cn v1.2 page2 pin function description pin number name function 1 ro receiver output. 2 /re receiver output enable. /re is low to enable the re ceiver; /re is high to disable the receiver. 3 de driver output enable: de is high to enable the driv er; de is low to disable the driver. 4 di driver input 5 gnd ground. 6 a non-inverting receiver input and non-inverting driver output. 7 b inverting receiver input and inverting driver o utput. 8 v cc power supply. function table transmitting inputs outputs /re de di b a x 1 1 0 1 x 1 0 1 0 0 0 x high-z high-z 1 0 x shutdown receiving inputs outputs /re de a-b ro 0 x -0.05v 1 0 x -0.2v 0 0 x open/shorted 1 1 1 x high-z 1 0 x shutdown
BL3085B www.belling.com.cn v1.2 page3 absolute maximum ratings parameter symbol rating units power supply v cc +7 v control input voltage /re, de -0.3 to v cc +0.3 v transmitter input voltage di -0.3 to v cc +0.3 v transmitter output voltage a, b -8 to +13 v receiver input voltage a, b -8 to +13 v receiver output voltage ro -0.3 to v cc +0.3 v operating temperature -40 to +85 dc electrical characteristics v cc =+5v5 G ,ta= -40 +85 typical values are v cc =+5v and ta 25 note 1 parameter symbol conditions min typ max units power supply vcc 4.5 5.5 v driver differential driver output(no load) v od1 figure 1 5 v differential driver output v od2 figure 1 r=27 1.5 v change in magnitude of differential output voltage note 2 ? v od figure 1 r=27 0.2 v driver common-mode output voltage v oc figure 1 r=27 3 v change in magnitude of common-mode voltage note 2 ? v oc figure 1 r=27 0.2 v input high voltage v ih1 de,di,/re 2.0 v input low voltage v il1 de,di,/re 0.8 v
BL3085B www.belling.com.cn v1.2 page4 di input hysteresis v hys 100 mv v in =12v 125 input current(a and b) i in4 de=gnd v cc =gnd or 5.25v v in =-7v -75 a -7v v Q out v Q cc -100 driver short-circuit output current i osd 0v v Q out 12v Q 100 ma receiver receiver differential threshold voltage v th -7v v Q cm 12v Q -200 -125 -50 mv receiver input hysteresis 40 mv receiver output high voltage v oh i o =-4ma,v id =-50mv v cc -1.5 v receiver output low voltage v ol i o =4ma,v id =-200mv 0.4 v three-state output current at receiver i ozr 0.4v v Q o 2.4v Q 1 a receiver input resistance r in -7v v Q cm 12v Q 96 k receiver output short-circuit current i osr 0v v Q ro v Q cc 7 95 ma supply current de=v cc 150 600 a supply current i cc no load ,/re=di= gnd or v cc de=gnd 185 600 a supply current in shutdown mode i shdn de=gnd, /re=vcc di=v cc or gnd 10 a note 1 all currents into the device are positive. all curre nts out of the device are negative. all voltages are referred to device ground unless otherwise noted. note 2 v od and v oc are the changes in v od and v oc , respectively, when the di input changes state. switching characteristics v cc =+5v5 G ,ta= -40 +85 typical values are at v cc =+5v ta 25 parameter symbol conditions min typ max units t dplh 450 800 driver input to output t dphl figure 3 and 5 r diff =54 c l1 =c l2 =100pf 450 800 ns
BL3085B www.belling.com.cn v1.2 page5 driver output skew |t dplh C t dphl | t dskew figure 3 and 5 r diff =54 c l1 =c l2 =100pf 100 ns driver rise or fall time t dr , t df figure 3 and 5 r diff =54 c l1 =c l2 =100pf 150 500 ns maximum data rate f max 250 kbps driver enable to output high t dzh figure 4 and 6 c l =100pf s2 closed 200 ns driver enable to output low t dzl figure 4 and 6 c l =100pf s1 closed 200 ns driver disable time from low t dlz figure 4 and 6 c l =15pf s1 closed 300 ns driver disable time from high t dhz figure 4 and 6 c l =15pf s2 closed 300 ns receiver input to output t rplh t rphl figure 7 and 9 ; rise and fall time of vid 15ns Q 450 800 ns |t rplh C t rphl | differential receiver skew t rskd figure 7 and 9 ; rise and fall time of vid 15ns Q 30 ns receiver enable to output low t rzl figure 2 and 8 c l =100pf s1 closed 20 50 ns receiver enable to output high t rzh figure 2 and 8 c l =100pf s2 closed 20 50 ns receiver disable time from low t rlz figure 2 and 8 c l =100pf s1 closed 80 150 ns receiver disable time from high t rhz figure 2 and 8 c l =100pf s2 closed 80 150 ns time to shutdown t shdn 50 300 ns driver enable from shutdown to output high t dzh(shdn) figure 4 and 6 c l =15pf s2 closed 200 ns driver enable from shutdown to output low t dzl(shdn) figure 4 and 6 c l =15pf s1 closed 200 ns receiver enable from shutdown to output high t rzh(shdn) figure 2 and 8 c l =100pf s2 closed 300 ns receiver enable from shutdown to output low t rzl(shdn) figure 2 and 8 c l =100pf s1 closed 300 ns
BL3085B www.belling.com.cn v1.2 page6 test circuits and timing diagrams figure 1 driver dc test load figure 2 receiver enable/disable timing test load figure 3 driver timing test circuit figure 4 driver enable/disable timing test load figure 5 driver propagation delays figure 6 driver enable and disable times
BL3085B www.belling.com.cn v1.2 page7 figure 7 receiver propagation delays figure 8 receiver enable and disable times figure 9 receiver propagation delay test circuit
BL3085B www.belling.com.cn v1.2 page8 package information sop8l
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