Description

The MAX4936A/MAX4937A are octal, high-voltage,transmit/receive (T/R) switches. The T/R switches arebased on a diode bridge topology, and the amount ofcurrent in the diode bridges can be programmed bythree digital inputs (S0, S1, and S2). Two control inputs(EN1 and EN2) allow enabling/disabling channels 1–4and channels 5–8, respectively. The MAX4936A includesthe T/R switch and grass-clipping diodes, performingboth transmit and receive operations. The MAX4937Aincludes just the T/R switch and performs the receiveoperation only.These devices feature low on-impedance in the entireultrasound frequency range with extremely low powerdissipation of 15mW (typ) per channel.The receive path for both devices is low impedanceduring low-voltage receive and high impedance duringhigh-voltage transmit, providing protection to the receivecircuitry. The low-voltage receive path is high bandwidth,low noise, low distortion, and low jitter.The MAX4936A SWC_ pins can be driven with high-voltagesignals using the anti-parallel diodes as grassclippers while connecting the SWB_ pins to the low-noiseamplifier (LNA). Connecting SWC_ to GND allowsthe internal anti-parallel diodes to be used as clamps.Grass-clipping diodes can then be connected to SWB_and the LNA to SWA_.Both devices are available in a small, 42-pin, 3.5mm x9mm TQFN package, and are specified over the commercial0°C to +70°C temperature range.ApplicationsHigh-Voltage Transmit and Low-Voltage IsolationMedical/Industrial ImagingUltrasound