AND8058/D

http://onsemi.com

2

2. Switch between two audio signals in a single phone,

one from a digital baseband detector, the other from

an analog baseband detector, to drive the final audio

output to an ear piece. In this example, it is assumed

that a multifunctional cell phone has both an analog

detector and a digital detector, one of which must be

selected to drive the final audio output to the ear

piece. The NLAS4599 selects the digital or analog

detector output, presenting very low impedance to

the driver amplifier for the selected device and very

high impedance to the deselected device.

Analog

Detector

Digital

Detector

(TDMA, CDMA, GSM)

Control Pin

Audio Amplifier

Figure 2. Switching Between Two Audio Signals

These two examples show how the NLAS4599 can be

used to select from two outputs, such as crystals and digital,

or analog signals under microprocessor control. The

NLAS4599 will stop or pass any signal between GND and

The device is usable beyond 100 MHz, since the 3 dB point

is beyond 150 MHz.

The NLAS44599

ON Semiconductor has designed a new device in even

smaller spaces with more functionality. The device is placed

in a new package type, being made available and accepted

by JEDEC, called the Fine Pitch Quad Flat No Lead package

(QFN). The specification falls under JEDEC MO–220,

dated January 2000. It calls for packages whose body sizes

range from 3 x 3 mm to 8 x 8 mm. The lead count goes from

4 to 56. The thickness (height off the board) is a maximum

of 1 mm.

ON Semiconductor put a new device, called the

NLAS44599, in a 3 x 3 package. The new device consists of

16 leads with a 0.5 mm pitch. Since the package is “no lead,”

there are no co–planarity issues and no solder bumps. The

user simply applies solder paste to the circuit board, places

the QFN, and uses IR re–flow soldering to complete the

mounting.

With this concept, we were able to put the equivalent of

Compared to the 4053 in TSSOP, this device is more than

four times as space efficient. With 16 pins, we were able to

construct two independent DPDT switches. These devices

are inherently bilateral. Signals can flow in either direction

and, once turned on, these devices offer almost zero

propagation delay.

See Figure 3 for an example of how to switch LVDS

signals.

–

+

GND

3.5 mA

Current Source

100

Ω

Transmission Wire or Traces

Xmitter

Receiver

+

–

+

–

Figure 3. Low Voltage Differential Signaling