•

Reverse Disconnect

•

Complies with SCSI, SCSI-2

and SPI-2 Standards

•

5pF Channel Capacitance

during Disconnect

•

Hot Plugging Capability

•−400mA Sourcing Current for

Termination

•

+100mA Sinking Current for

Active Negation

•

1V Dropout Voltage Regulator

•

100

µA Supply Current in

Disconnect Mode

•

Trimmed Termination Current

to 5%

•

Trimmed Impedance to 5%

•

Low Thermal Resistance

Surface Mount Packages

The UC5605 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 UC5605 is the ab-

sence of the negative clamps on the output lines and the disconnect input must

be at a logic-low for the terminating resistors to be disconnected. Parametri-

cally, the UC5605 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 UC5605 provides a disconnect feature which, when driven low, discon-

nects 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.

UC5605

9-Line Low Capacitance SCSI Active Terminator

FEATURES

DESCRIPTION

BLOCK DIAGRAM

Circuit Design Patented

3/97

UDG-94122