Design

Dual DPDT / Quad SPDT analogue switch improves signal integrity

22nd May 2017
Mick Elliott

A dual DPDT / quad SPDT analogue switch featuring low resistance of 0.37Ω at 2.7V in the compact 2.6 x 1.8 x 0.55 mm miniQFN16 package has been introduced by Vishay Intertechnology. Suitable for both analogue and digital signal switching in space-constrained consumer, medical, and industrial applications, the Vishay Siliconix DG2788A delivers improved resistance flatness, signal integrity, parasitic capacitance, and bandwidth.

While competing devices with similar resistance offer resistance flatness of 500mΩ, the device released today features flatness of 10mΩ, which results in improved THD of -100dB.

In addition, the DG2788A's parasitic capacitance CON of 26 pF and COFF of 14.5pF are 70 % lower, resulting in an over 3x higher -3dB bandwidth of 338MHz. The switch offers an extended voltage range of 5.5V to accommodate common 5V industrial designs.

For 5V operation, competing devices rely on larger package sizes to achieve resistance values below 0.5Ω.

The DG2788A is capable of routing high frequency wide swing pulsing signals. It supports > 80MHz rail to rail pulses with > 200mA load current, which is ideal for precision pulse width modulation power loads in designs such as shape-memory alloy (SMA) actuators.

The device provides signal switching in smartphones and tablets, medical equipment, modems and peripherals, and data storage; SMA optical image stabilisation in micro cameras; and can replace relays in portable instrumentation and industrial control and automation equipment.

The DG2788A features four independently selectable SPDT switches and two control inputs. All switches conduct equally well in both directions and can be used as multiplexers and de-multiplexers. The device offers break before make switching and power down protection.

It operates over a single 1.8V to 5.5V power supply, while its digital inputs have a 1.2V logic threshold to ensure low-voltage TTL/CMOS compatibility. The RoHS-compliant switch offers ESD tolerance > 2kV (human body model) and latch up current of 300mA per JESD78.

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