NEATSwitch analog switch for mobile phones

ST has an extensive portfolio to address complex application requirements. ST’s family of analog switches provides different applications with high performance characteristics – not just ON resistance (RON) and flat resistance (RFLAT), but also with regard to crosstalk, total harmonic distortion, attenuation and bandwidth.

ST’s SPDT (Single Pole Dual Throw) analog switches, are part of the expanding family of NEATSwitch (nano-speed, efficient power, application specific and tiny package) are widely used to direct audio signals and data between various functional blocks in portable applications like:
Amplified audio switching (for low-noise speakers) using STG3684A,
Small signal audio switching (to switch between baseband processor and ring tone generator) using STG3685 or STG3699A,
Bluetooth data switching (to switch between speaker and bluetooth codec) with STG3699A, and
Microphone switching (between external microphone and internal microphone) with STG3157 or STG3689.


Mobile phone analog switch application

RON characteristics: in the range of 0.5Ohm to 5Ohm
High speed: ­ 1.5ns propagation delay
Low T_ON and T_OFF characteristics: 40ns (approx)
Crosstalk and off-isolation: –60dB (min)
High bandwidth: 300MHz (for video switches)
Total harmonic distortion: 0.03% (typ)
Ultra low quiescent current consumption: <1µA
Break-before-make feature
Wide operating voltage range: 1.65V to 4.3V

The analog switch is comprised of a transmission gate (PMOS and MNOS, in parallel) with good matching between the PMOS and NMOS transistors.
The low ON resistance allows inputs to be connected to outputs with low insertion loss and high bandwidth. R_ON flatness specifies the variation in RON as Input Voltage (V_IN) is varied from 0V to V_CC.
A large R_FLAT specification implies mismatched PMOS/NMOS in the switch, which might result in varied attenuation with the input signal and subsequently, distortion of the audio signal.

High Bandwidth: for high performance audio signal switching and telecom routing applications
Low R_ON: preserves signal integrity and reduces the drive required to support audio and signal processing applications. (eg. maximum R_ON in STG3699A is 0.5Ohm)
Ultra-low quiescent current and low power dissipation: for battery-operated applications.
Break-Before-Make (BBM) feature:
prevents contention between switching channels in SPDT/SP3T
Operating temperature range: -55°C to +125°C:
to support stable operation over a wide range of temperatures.

The audio switches come in very small, efficient packages like QFN and Flip-Chip.
Quad switch QFN16 (2.5mm x 2.5mm)
Dual switch DFN10 (2.5mm x 1.3mm)

Part number	Description	Package
STG3684ADTR	Dual 0.5W SPDT	DFN10L 2.3 x 2
STG3699AUTR	Quad 0.5Ohm SPDT	QFN16L 2.5 x 2.5
STG3157CTR	Single 9Ohm SPDT	SOT323-6L
STG3685BJR	Dual 0.5Ohm SPDT	Flip-Chip 9
STG3689DTR	Dual 0.9Ohm SPST	DFN10L 2.5 x 1.3