SN74LVC1G08DCKR

The SN74LVC1G08DCKR from Texas Instruments is a single 2-input positive-AND gate housed in an ultra-compact SC-70-5 (SOT-353) package, performing the Boolean function Y = A AND B (or Y = NOT(A OR B) in DeMorgan equivalent form) in positive logic.

The device is part of the 74LVC (Low-Voltage CMOS) family, designed to operate over a wide VCC range of 1.65V to 5.5V. This makes it suitable for 1.8V, 2.5V, 3.3V, and 5V logic systems. The inputs accept voltages up to 5.5V regardless of VCC, enabling the device to serve as a voltage translator: a 5V input signal can drive the AND gate while the output swings to the VCC level (e.g., 3.3V), providing down-translation without level shifter ICs.

Key performance specifications include: maximum propagation delay of 3.6ns at 3.3V (4ns at 5V) with 50pF load, output drive current of plus/minus 24mA at 3.3V and plus/minus 32mA at 5V in push-pull CMOS configuration, and maximum quiescent current of 10uA. The push-pull output provides strong drive with rail-to-rail swing, unlike open-drain alternatives that require external pullup resistors.

The Ioff feature is critical for mixed-voltage and hot-swap applications: when VCC is at 0V (device powered down), the Ioff circuitry disables the output, preventing damaging current from flowing back through the device from the input or output pins. This allows the device to be used in systems where different voltage domains may be powered independently, and supports live insertion (hot-swap) of cards or modules.

The DCK suffix denotes the SC-70-5 package, while the R suffix denotes tape and reel packaging with 3,000 units per reel. The device is also available in SOT-23-5 (DBV), SOT-5X3 (DRL), DSBGA-5 (YZP), USON-6 (DRY), X2SON-5 (DPW, ultra-small 0.8×0.8mm), and X2SON-6 (DSF) packages. The device is RoHS compliant, MSL Level 1, and classified as EAR99. Operating temperature range is -40C to 125C (TA), suitable for industrial and automotive-adjacent applications.

The SN74LVC1G08DCKR implements a 2-input AND logic function using CMOS transistor-level circuitry in a single-gate configuration.

CMOS AND Gate Implementation: A CMOS AND gate is typically implemented by combining a NAND gate with an inverter. The NAND gate uses complementary PMOS and NMOS transistor networks: the PMOS network connects VCC to the output when either input is LOW (parallel PMOS configuration), while the NMOS network connects the output to GND only when both inputs are HIGH (series NMOS configuration). The subsequent inverter stage complements the NAND output to produce the AND function: Y = A AND B.

Voltage Translation: The 5.5V-tolerant input capability works because the input protection and level-shifting circuitry can accept voltages higher than VCC without forward-biasing internal parasitic diodes. When a 5V signal is applied to an input while VCC = 3.3V, the internal circuitry correctly recognizes the logic level and drives the output to VCC (3.3V). This provides unidirectional down-translation from 5V to 3.3V logic. Note that up-translation (VCC = 5V with 3.3V inputs) is also supported since the 3.3V HIGH level exceeds the VIH threshold at 5V VCC.

Ioff Partial Power-Down: The Ioff circuitry consists of isolation transistors that disconnect the output stage when VCC drops below a threshold. When VCC = 0V, the Ioff circuitry ensures that the output enters a high-impedance state, preventing current from flowing from the input pins (which may still be at logic HIGH from another active domain) through internal ESD diodes or parasitic paths to the VCC rail. This is essential for: (1) mixed-voltage systems where some domains are powered while others are not, (2) hot-swap applications where cards are inserted/removed while power is applied, and (3) battery backup systems where the main logic is powered down but interface signals remain active.

Output Drive: The push-pull CMOS output stage uses complementary PMOS (pull-up) and NMOS (pull-down) transistors. The PMOS transistor sources current when driving the output HIGH (up to VOH specification), and the NMOS transistor sinks current when driving the output LOW (up to VOL specification). The plus/minus 24mA drive at 3.3V provides sufficient current to drive multiple logic inputs, short PCB traces, and moderate capacitive loads without additional buffering.

Propagation Delay: The 3.6ns maximum propagation delay at 3.3V (50pF load) includes both the NAND and inverter stages. The delay is relatively insensitive to VCC within the operating range due to the CMOS design. At 5V VCC, the increased gate overdrive reduces propagation delay to 4ns maximum while increasing output drive to plus/minus 32mA.