complies with scsi, scsi-2 and spi-2 standards 5pf channel capacitance during disconnect meets scsi hot plugging - 400ma sourcing current for termination +100ma sinking current for active negation 1v dropout voltage regulator logic high command disconnects all termination lines 100 m a supply current in disconnect mode trimmed termination current to 5% trimmed impedance to 5% low thermal resistance surface mount packages the uc5612 provides 9 lines of active termination for a scsi (small computer systems interface) parallel bus. the scsi standard recommends active termi- nation at both ends of the cable segment. the only functional differences between the uc5603 and uc5612 is the ab- sence of the negative clamps on the output lines. parametrically, the uc5612 has a 5% tolerance on impedance and current compared to a 3% tolerance on the uc5603. custom power packages are utilized to allow normal operation at full power (2 watts). the uc5612 provides a disconnect feature which, when opened or driven high, disconnects all terminating resistors, disables the regulator and greatly reduces standby power consumption. the output channels remain high impedance even without termpwr applied. a low channel capacitance of 5pf allows interim points of the bus to have little to no effect on the signal integrity. internal circuit trimming is utilized, first to trim the impedance to a 5% tolerance, and then most importantly, to trim the output current to a 5% tolerance, as close to the maximum scsi specification as possible. this maximizes the noise mar- gin in fast scsi operation. other features include thermal shutdown and cur- rent limit. this device is offered in low thermal resistance versions of the industry stand- ard 16 pin narrow body soic, 16 pin zip (zig-zag in line package) and 24 pin tssop. uc5612 9-line low capacitance scsi active terminator features description block diagram circuit design patented 3/97 udg-94133
absolute maximum ratings termpwr voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7v signal line voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . 0v to +7v regulator output current . . . . . . . . . . . . . . . . . . . . . . . . . . 0.6a storage temperature . . . . . . . . . . . . . . . . . . . - 65c to +150c operating temperature . . . . . . . . . . . . . . . . . - 55c to +150c lead temperature (soldering, 10 sec.) . . . . . . . . . . . . . +300c recommended operating conditions termpwr voltage . . . . . . . . . . . . . . . . . . . . . . . . . 3.8v to 5.25v signal line voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 0v to +5v disconnect input voltage . . . . . . . . . . . . . . . . . . 0v to termpwr connection diagrams dil-16 (top view) n or j package uc5612 * dp package pin 5 serves as signal ground; pins 4, 12, 13 serve as heatsink/ground. * pwp package pin 9 serves as signal ground; pins 5, 6, 7, 8, 17, 18, 19, and 20 serve as heatsink/ground. zip-16 (top view) z package soic-16 (top view) dp package tssop-24 (top view) pwp package note: drawings are not to scale. unless otherwise specified all voltages are with respect to ground. currents are positive into, negative out of the speci- fied terminal. consult packaging section of unitrode integrated circuits dat- abook for thermal limitations and considerations of packages. 2
parameter test conditions min typ max units supply current section termpwr supply current all termination lines = open 17 23 ma all termination lines = 0.5v 200 225 ma power down mode discnct = open 100 150 m a output section (termination lines) terminator impedance d i line = -5ma to -15ma 104.5 110 115.5 ohms output high voltage 2.65 2.9 3.1 v max output current v line = 0.5v t j = 25 c -20.3 -21.5 -22.4 ma 0c < t j < 70c -19.8 -21.5 -22.4 ma max output current v line = 0.5v, trmpwr = 4v (note 1) t j = 25 c -19.5 -21.5 -22.4 ma 0c < t j < 70c -19.0 -21.5 -22.4 ma v line = 0.2v, trmpwr = 4v to 5.25v 0c < t j < 70c -21.6 -24.0 -25.4 ma output leakage discnct = 4v trmpwr = 0v to 5.25v reg = 0v v line = 0 to 4v 10 400 na v line = 5.25v 100 m a reg = open v line = 0v to 5.25v 10 400 na output capacitance discnct = open (note 2) (dp package) 5 6 pf regulator section regulator output voltage 2.7 2.9 3.1 v all termination lines = 4v 2.7 2.9 3.1 v line regulation trmpwr = 4v to 6v 10 20 mv drop out voltage all termination lines = 0.5v 1.0 1.2 v short circuit current reg = 0v -200 -400 -600 ma sinking current capability reg = 3.5v 75 100 400 ma thermal shutdown 170 c thermal shutdown hysteresis 10 c disconnect section disconnect threshold 1.1 1.4 1.7 v input current discnct = 0v -10 -20 m a electrical characteristics unless otherwise stated, these specifications apply for t a = 0c to 70c. trmpwr = 4.75v, discnct = 0v, t a = t j . uc5612 note 1: measuring each termination line while other 8 are low. note 2: guaranteed by design. not 100% tested in production. figure 1: typical scsi bus configurations utilizing 2 uc5612 devices application information udg-94134 3
application information (cont.) unitrode corporation 7 continental blvd. merrimack, nh 03054 t el. (603) 424-2410 fax (603) 424-3460 uc5612 figure 2: typical wide scsi bus configurations utilizing 3 uc5612 devices. udg-94135 4
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