12-Bit To 24-Bit Multiplexed Bus Exchanger
with 3-State Outputs
• PI74ALVCH16271 is designed for low voltage operation,
VCC = 2.3V to 3.6V
• Hysteresis on all inputs
www.DataS•heTeyt4pUic.caolmVOLP (Output Ground Bounce)
< 0.8V at VCC = 3.3V, TA = 25°C
• Typical VOHV (Output VOH Undershoot)
< 2.0V at VCC = 3.3V, TA = 25°C
• Bus Hold retains last active bus state during 3-State,
eliminating the need for external pullup resistors
• Industrial operation at 40°C to +85°C
• Packages available:
56-pin 240 mil wide plastic TSSOP (A56)
56-pin 300 mil wide plastic SSOP (V56)
Logic Block Diagram
Pericom Semiconductor’s PI74AVC series of logic circuits are
produced using the Company’s advanced 0.35 micron CMOS
technology, achieving industry leading speed.
This 12-bit to 24-bit multiplexed bus exchanger is designed for 2.3V
to 3.6V VCC operation.
The PI74ALVCH16271is intended for applications in which two
separate data paths must be multiplexed onto, or demultiplexed
from, a single data path. This device is particularly suitable as an
interface between conventional DRAMs and high-speed
Data is stored in the internal A-to-B registers on the low-to-high
transition of the clock (CLK) input, provided clock-enable (CLKENA)
inputs are low. Proper control of these inputs allows two sequential
12-bit words to be presented as a 24-bit word on the B port.
To maximize memory access throughput, transparent latches in
the B-to-A path allow asynchronous operation. These latches
transfer data when the latch-enable (LE) inputs are low. The select
(SEL) line selects 1B or 2B data for the A outputs. Data flow is
controlled by the active-low output enables (OEA, OEB).
To ensure the high-impedance state during power up or power
down, OE should be tied to VCC through a pullup resistor, the
minimum value of the resistor is determined by the current-sinking
capability of the driver.
Active bus-hold circuitry is provided to hold unused or floating
data inputs at a valid logic level.
1 PS8360 02/02/99