SN74HCT138

· Inputs Are TTL-Voltage Compatible
· Designed Specifically for High-Speed Memory Decoders and Data Transmission Systems
· Incorporate Three Enable Inputs to Simplify Cascading and/or Data Reception
· Package Options Include Plastic Small-Outline (D), Thin Shrink Small-Outline (PW), and Ceramic Flat (W) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (N) and Ceramic (J) 300-mil DIPs

Supply voltage range, V_CC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 0.5 V to 7 V
Input clamp current, I_IK (V_I < 0 or V_I > V_CC) (see Note 1) . . . . . . .  . . . . . . . . . . . ±20 mA
Output clamp current, I_OK (V_O < 0 or V_O > V_CC) (see Note 1) . . . . . . . .. . . . . . . . ±20 mA
Continuous output current, I_O (V_O = 0 to V_CC) . . . . . . . . . . . . . . . . . . . . . . . . . . . ±25 mA
Continuous current through V_CC or GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±50 mA
Package thermal impedance, _JA (see Note 2): D package . . . . . . . . . .. . . . . . . 113°C/W
                                                                          N package . . . . . . . . . . . . . . . . . . 78°C/W
Storage temperature range, T_stg . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . 65°C to 150°C

† Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES: 1. The input and output voltage ratings may be exceeded if the input and output current ratings are observed.
2. The package thermal impedance is calculated in accordance with JESD 51, except for through-hole packages, which use a trace length of zero.

The SN74HCT138 are designed for high-performance memory-decoding or data-routing applications requiring very short propagation delay times. In high-performance memory systems, these decoders can minimize the effects of system decoding. When employed with high-speed memories utilizing a fast enable circuit, the delay times of these decoders and the enable time of the memory are usually less than the typical access time of the memory. This means that the effective system delay introduced by the decoders is negligible.

The conditions of the SN74HCT138 at the binary-select inputs and the three enable inputs select one of eight output lines. Two active-low (G) and one active-high (G) enable inputs reduce the need for external gates or inverters when expanding. A 24-line decoder can be implemented without external inverters and a 32-line decoder requires only one inverter. An enable input can be used as a data input for demultiplexing applications. The SN54HCT138 is characterized for operation over the full military temperature range of 55°C to 125°C. The SN74HCT138 is characterized for operation from 40°C to 85°C.