BiCMOS Technology With Low Quiescent

Power

Buffered Inputs

Noninverted Outputs

Input/Output Isolation From VCC

Controlled Output Edge Rates

48-mA Output Sink Current

Output Voltage Swing Limited to 3.7 V

SCR Latch-Up-Resistant BiCMOS Process

and Circuit Design

Packaged in Plastic Small-Outline Package

description

The CD74FCT843A is a 9-bit, bus-interface,

D-type latch with 3-state outputs, designed

specifically for driving highly capacitive or relatively low-impedance loads. It is particularly suitable for

implementing buffer registers, I/O ports, bidirectional bus drivers, and working registers.

The device uses a small-geometry BiCMOS technology. The output stage is a combination of bipolar and CMOS

transistors that limits the output high level to two diode drops below VCC. This resultant lowering of output swing

(0 V to 3.7 V) reduces power-bus ringing [a source of electromagnetic interference (EMI)] and minimizes VCC

bounce and ground bounce and their effects during simultaneous output switching. The output configuration

also enhances switching speed and is capable of sinking 48 mA.

The CD74FCT843A outputs are transparent to the inputs when the latch-enable (LE) input is high. The latches

are transparent D-type latches. When LE goes low, the data is latched. The output-enable (OE) input controls

the 3-state outputs. When OE is high, the outputs are in the high-impedance state. The latch operation is

independent of the state of the output enable. This device, having preset (PRE) and clear (CLR), are ideal for

parity-bus interfacing. When PRE is low, the outputs are high if OE is low. PRE overrides CLR. When CLR is

low, the outputs are low if OE is low. When CLR is high, data can be entered into the latch. The device provides

noninverted outputs.

OE does not affect the internal operations of the latch. Previously stored data can be retained or new data can

be entered while the outputs are in the high-impedance state.

The CD74FCT843A is characterized for operation from 0°C to 70°C.