DM74AS645N

Logic - Buffers, Drivers, Receivers, Transceivers

The DM74AS645N is a monolithic integrated circuit for use in high speed TTL logic applications. It is a high drive, octal bus driver consisting of six 3-state non-inverting drivers, one 3-state inverting driver, and an output latch. The drivers are capable of 6 mA sink and sources, and 32 mA pendown with the added assistance of external pullup resistors. The outputs of the drivers are synchronized with the latch which is enabled by the LE pin.

Application Field

The DM74AS645N is specifically used in high speed TTL logic applications as a driver. It is used as an external memory input/output and system control interface. It also functions as a secondary latch, where it controls outputs from other primary latches. Other applications include 12 Mb/s RS232 data interface, data bussing, handshaking and multiplexing.

Function and Working Principles

The DM74AS645N is a high-drive octal bus driver, with six non-inverting and one inverting 3-state outputs, and an output latch. The circuitry is monolithic, with 6 mA sink and 3.2 mA sources. A 5V supply provides 25mA/pin@ 75Ω/pin connection. Each output has a minimum on-off output impedance of 1.5kΩ/√2.

The outputs, which can be either active high or low, are synchronized with the output latch. The LE pin is used to enable the latch, which causes the outputs to be synchronized. This is done by making the LE pin high, which sets the output latches, and then making the LE pin low, which results in the outputs being latched.

The outputs are also ESD protected, and feature low power dissipation. The DM74AS645N also features a standby mode, in which the device is operational but all outputs are shut off in order to conserve power.

The DM74AS645N is ideal for a variety of applications, including memory input/output and system control interfaces, 12 Mb/s RS232 data interfaces, data bussing, handshaking, and multiplexing. This logic device is also suitable for use in systems that require high speed TTL logic, with the added benefit of having an onboard output latch.