UCC5620 description UCC5620 provides 27 lines of active termination for a scsi (small com - puter systems interface) parallel bus. the scsi standard recommends active termination at both ends of the cable. the UCC5620 is ideal for high performance 5v scsi systems. during disconnect the supply current is typically only 100 a, which makes the ic attractive for lower powered systems. the UCC5620 is designed with a l ow channel capacitance of 2.5pf, which eliminates effects on signal integrity from disconnected terminators at interim points on the bus. the power amplifier output stage allows the UCC5620 to source full ter - mination current and sink active negation current when all termination lines are actively negated. the UCC5620, as with all unitrode terminators, is completely hot plugga - ble and appears as high impedance at the teminating channels with v trmpwr = 0v or open. internal circuit trimming is utilized, first to trim the 110 ? impedance, and then most importantly, to trim the output current as close to the maximum scsi-3 specification as possible, which maximizes noise margin in fast scsi operation. other features include thermal shutdown and current limit. this device is offered in low thermal resistance versions of the industry standard 36-pin wide body qsop (mwp) and 48-pin lqfp (fqp). consult qsop-36 or lqfp-48 packaging diagram for exact dimensions. 27-line scsi terminator block diagram features ? complies with scsi, scsi-2, scsi-3, spi and fast-20 (ultra) standards ? 2.5pf channel capacitance during disconnect ? 100ma supply current in disconnect mode ? 4v to 7v operation ? 110 termination ? completely meets scsi hot plugging ? ?900ma sourcing current for termination ? +500ma sinking current for active negation ? logic command disconnects all termination lines ? trimmed impedance to 5% ? current limit and thermal shutdown protection slus287a - october 1999 udg-96109 circuit design p atented
2 UCC5620 termpwr voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7v signal line voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 0v to +7v regulator output current . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5a storage temperature . . . . . . . . . . . . . . . . . . . ? 65 c to +150 c junction temperature . . . . . . . . . . . . . . . . . . . ? 55 c to +150 c lead temperature (soldering, 10 sec.). . . . . . . . . . . . . +300 c currents are positive into, negative out of the specified termi - nal. consult packaging section of databook for thermal limita - tions and considerations of packages. absolute maximum ratings discnct gnd line21 line20 line19 line7 line23 line9 gnd line27 gnd line24 line25 line26 line8 gnd line10 reg gnd gnd line11 line12 14 13 12 11 10 9 8 7 6 5 4 3 2 1 23 24 25 26 27 28 29 30 31 32 33 34 35 36 18 17 16 15 line15 line3 line4 19 20 21 22 line13 line14 line1 line2 trmpwr line18 line17 line16 line22 line5 line6 connection diagram ssop-36 (top view) mwp package electrical characteristics unless otherwise stated, these specifications apply for t a = 0c to 70c, trmpwr = 4.75v, discnct = 0v, t a =t j . parameter test conditions min typ max units supply current section trmpwr supply current all termination lines = open 1 2 ma all termination lines = 0.2v 630 650 ma power down mode discnct = trmpwr 100 200 a 48 47 46 45 1 44 43 42 41 40 39 38 37 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 36 35 34 33 32 31 30 29 28 27 26 25 line 22 line 5 line 6 line 7 line 8 hs/gnd n/c line 24 line 9 hs/gnd hs/gnd reg line 19 line 20 line 21 trmpwr hs/gnd line 17 line 18 line 16 line 4 line 15 line 2 line 3 n/c line 12 line 13 line 14 hs/gnd line 27 line 26 line 25 discnct1 hs/gnd line 10 n/c line 11 hs/gnd hs/gnd hs/gnd line 23 hs/gnd hs/gnd line 1 hs/gnd hs/gnd hs/gnd n/c lfqp-48 (top view) fqp package
3 UCC5620 electrical characteristics unless otherwise stated, these specifications apply for t a = 0c to 70c, trmpwr = 4.75v, discnct = 0v, t a =t j . parameter test conditions min typ max units output section (termination lines) termination impedance (note 3) 104.5 110 115.5 ? output high voltage (note 1) 2.6 2.8 3.0 v max output current v line = 0.2v, t j = 25c ? 22.1 ? 23.3 ? 24 ma v line = 0.2v ? 20.7 ? 23.3 ? 24 ma v line = 0.2v, trmpwr = 4v, t j = 25c (note 1) ? 21 ? 23 ? 24 ma v line = 0.2v, trmpwr = 4v (note 1) ? 20 ? 23 ? 24 ma v line = 0.5v ? 22.4 ma output leakage discnct = 2.4v, trmpwr = 0v to 5.25v 10 400 na output capacitance discnct = 2.4v (note 2) 2.5 4 pf regulator section regulator output voltage 2.6 2.8 3.0 v drop out voltage all termination lines = 0.2v 0.4 0.8 v short circuit current v reg = 0v ? 650 ? 900 ?1300 ma sinking current capability v reg = 3.5v 300 500 900 ma thermal shutdown 170 c thermal shutdown hysteresis 10 c disconnect section disconnect threshold 0.8 1.5 2.0 v input current discnct = 0v ?20 ?60 a note 1: measuring each termination line while other 26 are low (0.2v). note 2: guaranteed by design. not 100% tested in production. note 3: tested by measuring i out with v out = 0.2v and v out with no load, then calculate: () z vnl v iatv out out = ? .. . . 02 02 pin descriptions discnct: taking this pin high or leaving it open causes all channels to become high impedance, and the chip to go into low-power mode; a low state allows the channels to provide normal termination. gnd: ground reference for the ic. line1 - line27: 110 ? termination channels. reg: output of the internal 2.7v regulator. trmpwr: power for the ic.
4 UCC5620 unitrode corporation 7 continental blvd. merrimack, nh 03054 tel. (603) 424-2410 fax (603) 424-3460 trmpwr reg to scsi bus trmpwr data bytes 1 and 2 +2 parity bits l1 4.7 f 4.7 f discnct to drivers and receivers UCC5620 control bits l27 figure 1. typical wide scsi bus configuration using the UCC5620 application information udg-98188
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