Electronic Design

Tiny Multiplexers, Dual CMOS Bus Switches Consume Virtually No Board Space

The NC7SZ157P6 is a high-performance, 2-to-1, noninverting multiplexer. Unusually small, this device is housed in a six-lead (SC70-6) surface-mount package with a footprint of 2.1 by 2.0 mm. This new multiplexer is a member of Fairchild's ultra-high speed (UHS) TinyLogic portfolio. The device compares quite favorably with the industry alternative of a single 157 multiplexer function in an eight-lead SSOP8 package. Only 50% of the board area is required, however. Because of its compact size, the NC7SZ157P6 will save designers crucial board space. Designs expected to benefit include mobile phones, pagers, palm computers, digital assistants, PDAs, notebooks, and desktop computers.

To achieve ultra-high speed with high output drive, the NC7SZ157P6 is fabricated with advanced CMOS technology. Static-power-dissipation is low over a broad VCC operating range (from 1.65 to 5.5 V). Propagation delay is typically 5.0 ns (50 pF at 5 V VCC). Quiescent current is 10 µA. Other features include a power-down mode, high impedance I/Os, overvoltage-tolerant inputs to facilitate 5- to 3-V conversion, and noise/EMI reduction circuitry.

As part of the company's TinyLogic family, Fairchild also is introducing four new dual-CMOS bus switches. They're mounted in eight-lead (US8) surface-mount packages measuring just 2.1 by 3.1 mm, including the leads. These switches are well-suited for applications in high-speed computing devices.

Included in this new line of switch products are the NC7WB3306K8, NC7WBD3306K8, NC7WB3125K8, and NC7WBD3125K8. The series provides an intermediate choice between the single packaged switch and a larger packaged TSSOP for performing fundamental signal control and routing tasks.

The quiescent supply current is just 3 µA and propagation delay is 0.25 ns typical. Each model is an all-CMOS FET, two-bit bus switch with TTL-compatible inputs. Furthermore, each member of this line is organized as a set of independent bus switches with independent bus-enable controls.

Single- and dual-gate logic and switch bus switches such as these can provide function add-ons where needed. Consequently, long and undesirable signal routings can be eliminated. Typical applications include the addition of two extra parallel bits at a connector interface, and control circuitry for selecting one of two alternate clock signals.

The devices offer designers a footprint that is 53% smaller than the closest alternative. With maximum heights of 0.9 mm, these switches are ideal for use in low-profile systems such as laptops, portable CD players, disk drives, pagers, radios, cell phones, digital cameras, portable computers, docking stations, PDAs, and PCMCIA cards. With a lead pitch of 0.5 mm, the US8 package allows for increased manufacturing yields over devices in packages with tighter lead pitches.

The NC7WBD3306K8 provides flow-through configuration for the I/O paths. Plus, it features isolation, and in the on mode, low loss—typically 3 Ω at 5 V VCC. Therefore, it's useful for digital logic (I/O) paths.

An internal VCC series diode for I/O-level conversion is included in the NC7WBD3306K8. This device is intended for applications requiring level translation from 5- to 3-V logic, in boards where I/Os between functions are at different logic levels. The input and output plus the gate of one switch are brought out to one side of the package. The corresponding connections of the second switch are brought out at the other side of the package.

Said to be unique in the marketplace are the NC7WB3125K8 and NC7WBD3125K8. They are identical to the first pair except that they provide "flow-through" pinouts. This means that the inputs and outputs are brought out at the opposite sides of the package in a bidirectional configuration.

Offered in quantities of 10,000, the NC7SZ157P6 is priced at $0.32 each. Samples and production quantities are available now. Also sold in 10,000-piece quantities, the NC7WB3306K8 and NC7WB3125K8 are priced at $0.42 each. The NC7WBD3306K8 and the NC7WBD3125K8 are priced at $0.46 in 10,000-piece quantities. Samples and production quantities are available now.

Fairchild Semiconductor, 333 Western Ave., S. Portland, ME 04106; (888) 522-5372; fax (972) 910-8036; Internet: www.fairchildsemi.com.

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