The SN74CB3T16211 is a high-speed TTL-compatible FET bus switch with low ON-state
resistance (ron), allowing for minimal propagation delay. The device fully supports mixed-mode signal operation on all data I/O ports by providing voltage translation that tracks VCC. The SN74CB3T16211 supports systems using 5-V TTL, 3.3-V LVTTL, and 2.5-V CMOS switching standards, as well as user-defined switching levels.
The I/O port of this device has a pullup current source that maintains the output voltage
at VCC when the device is ON, and the input is greater than or equal to VCC – 1. Because of the pullup current source, the output voltage level may be less than VCC when the operating frequency is low and the I/O port is connected to a pulldown resistor. In order to maintain the output voltage at VCC, a pullup resistor must be connected to VCC instead of a pulldown resistor to ground.
The SN74CB3T16211 is organized as two 12-bit bus switches with separate output-enable
(1OE, 2OE) inputs. It can be used as two 12-bit bus switches or as one 24-bit bus switch. When OE is low, the associated 12-bit bus switch is ON, and the A port is connected to the B port, allowing bidirectional data flow between ports. When OE is high, the associated 12-bit bus switch is OFF, and a high-impedance state exists between the A and B ports.
This device is fully specified for partial-power-down applications using Ioff. The Ioff feature ensures that damaging current will not backflow through the device when it is powered down. The device has isolation during power off.
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
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