Part A
74LCX244MTC
オンセミコンダクター社
- Lifecycle
- Active
- Stock
- 5042 個数
- Series
- ロジック - バッファ、ドライバ、レシーバ、トランシーバ
Replacement verdict
Compatible functional replacement candidate
The 74LCX244MTC and 74LCX240TTR are both low-voltage CMOS octal buffers from the LCX family, sharing identical TSSOP-20 footprints, 2.0 V to 3.6 V supply ranges, and 5 V tolerant inputs. The primary distinction lies in their output configurations: the 74LCX244MTC provides non-inverting 3-state outputs, while the 74LCX240TTR delivers inverting 3-state outputs. This polarity difference requires careful consideration in signal-path design, but the devices remain functionally interchangeable in applications where logic inversion is acceptable or can be compensated elsewhere in the circuit.
Output Polarity
Validation required
Package Type
High match
Supply Voltage Range
High match
Channel Count
High match
Parts at a glance
Part B
74LCX240TTR
RFE/フューゼテック
- Lifecycle
- Active
- Stock
- 4104 個数
- Package
- TSSOP-20
- Series
- ロジック - バッファ、ドライバ、レシーバ、トランシーバ
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74LCX244MTC | 74LCX240TTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver, non-inverting, 3-state | Octal Buffer/Line Driver, inverting, 3-state | The 244 provides non-inverted outputs while the 240 inverts the signal; this polarity difference prevents direct functional substitution without logic redesign. |
| Output Polarity | Non-inverting | Inverting | Signal polarity determines whether the output matches or complements the input, which is critical for correct data flow in a circuit. |
| Enable Control | Active-Low Output Enable (dual, one per nibble) | Active-Low Output Enable (dual, one per nibble) | Both use active-low enables, but the inverted outputs of the 240 mean the enable logic interacts differently with downstream stages. |
| Supply Voltage Range | 2.0 V to 3.6 V | 2.0 V to 3.6 V | Matching supply ranges ensure both devices operate in the same low-voltage logic environments without level shifting. |
| Output Drive Current | ±24 mA | ±24 mA | Identical drive strength means both can drive the same load without additional buffering. |
| Propagation Delay | ~6.5 ns at 3.3 V | ~6.5 ns at 3.3 V | Similar propagation delay ensures comparable timing performance in high-speed signal paths. |
| Package Type | TSSOP-20 | TSSOP-20 | Same package footprint allows drop-in PCB compatibility without layout changes. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Identical temperature ratings ensure both parts function reliably in the same environmental conditions. |
| Input Type | CMOS/TTL compatible | CMOS/TTL compatible | Compatible input thresholds allow both devices to interface with the same logic families. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74LCX244MTC | 74LCX240TTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74LCX | 74LCX |
| Part Status | Active | Obsolete |
| Logic Type | Buffer, Non-Inverting | Buffer, Inverting |
| Number of Elements | 2 | 2 |
| Number of Bits per Element | 4 | 4 |
| Output Type | 3-State | 3-State |
| Current - Output High Low | - | 24mA, 24mA |
| Voltage - Supply | 2V ~ 3.6V | 2V ~ 3.6V |
| Operating Temperature | -40°C ~ 85°C (TA) | -55°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Base Product Number | 74LCX244 | - |
| Current - Output High, Low | 24mA, 24mA | - |
| Packaging | Tube | - |
Frequently asked questions
What are the main functional differences between the 74LCX244MTC and the 74LCX240TTR?
The 74LCX244MTC is an octal buffer/line driver with 3-state outputs, featuring non-inverting outputs and two active-low output enable pins (1OE and 2OE). The 74LCX240TTR is an octal buffer/line driver with 3-state outputs, featuring inverting outputs and two active-low output enable pins (1OE and 2OE). The primary difference is the output polarity: the 74LCX244 provides non-inverted signals, while the 74LCX240 provides inverted signals.
Are the 74LCX244MTC and 74LCX240TTR pin-to-pin compatible?
Yes, both devices are pin-to-pin compatible. They share the same 20-pin package footprint and identical pinout assignments for inputs, outputs, enables, VCC, and GND. However, because the 74LCX240TTR inverts the signal, a direct substitution in an existing design will invert the logic unless the system logic is adjusted accordingly.
What are the operating voltage and logic level specifications for these devices?
Both the 74LCX244MTC and 74LCX240TTR operate over a supply voltage range of 2.0 V to 3.6 V. They are designed for low-voltage applications with 5 V tolerant inputs, allowing them to interface with 5 V logic systems while operating at 3.3 V or lower. Typical propagation delay is approximately 5.5 ns at 3.3 V.
What is the difference in output drive current between the two parts?
Both devices provide identical output drive capability. They are specified with ±24 mA output drive at 3.0 V, making them suitable for driving bus lines and high-capacitive loads. The drive strength is the same because both use similar output stage designs, differing only in the added inversion stage for the 74LCX240TTR.
What package types are available for the 74LCX244MTC and 74LCX240TTR?
The 74LCX244MTC is supplied in a 20-pin TSSOP (Thin Shrink Small Outline Package) as indicated by the "MTC" suffix. The 74LCX240TTR is supplied in a 20-pin TSSOP as indicated by the "TTR" suffix, which typically denotes tape and reel packaging. Both are surface-mount packages with the same body dimensions and lead pitch.
Can the 74LCX244MTC and 74LCX240TTR be used interchangeably in a design?
They can be used interchangeably only if the logic inversion is accounted for. Since the 74LCX240TTR inverts the input signal and the 74LCX244MTC does not, replacing one with the other will invert the output logic state. In designs where signal polarity is critical, additional inversion or logic changes are required. Otherwise, the electrical characteristics, pinout, and package are identical.
What are the typical applications for the 74LCX244MTC and 74LCX240TTR?
Both devices are used as octal buffers/line drivers in bus-oriented systems, memory address drivers, clock drivers, and other applications requiring high-speed, low-power 3-state buffering. The 74LCX244MTC is chosen when non-inverting buffering is needed, while the 74LCX240TTR is selected when signal inversion is required, such as in differential signal generation or active-low logic interfaces.
Do both devices have the same 3-state output enable control logic?
Yes, both devices feature two active-low output enable pins (1OE and 2OE) that control the 3-state outputs. When either enable pin is high, the corresponding outputs are placed in a high-impedance state. The enable control logic and pin assignments are identical for both the 74LCX244MTC and 74LCX240TTR.