Octal High-Voltage Transmit/Receive Switches

The MAX4936–MAX4939 are octal, high-voltage, transmit/receive (T/R) switches. The T/R switches are based on a diode bridge topology, and the amount of current in the diode bridges can be programmed through an SPI™ interface. All devices feature a latch-clear input to asynchronously turn off all T/R switches and put the device into a low-power shutdown mode. The MAX4936/MAX4938 include the T/R switch and grass-clipping diodes, performing both transmit and receive operations. The MAX4937/MAX4939 include just the T/R switch and perform the receive operation only.

The MAX4936/MAX4938 transmit path is low impedance during high-voltage transmit and high impedance during low-voltage receive, providing isolation between the transmit and receive circuitry. The high-voltage transmit path is high bandwidth, low distortion, and low jitter.

The receive path for all devices is low impedance during low-voltage receive and high impedance during high-voltage transmit, providing protection to the receive circuitry. The low-voltage receive path is high bandwidth, low noise, low distortion, and low jitter. Each T/R switch can be individually programmed on or off, allowing these devices to be used as receive path multiplexers also.

The MAX4936/MAX4937 feature clamping diodes to protect the receiver input from voltage spikes due to leakage currents flowing through the T/R switches during transmission. The MAX4938/MAX4939 do not have clamping diodes and rely on clamping diodes integrated in the receiver front end.

All the devices are available in a small, 56-pin, 5mm x 11mm TQFN package, and are specified over the commercial 0°C to +70°C temperature range.

Applications

* High-Voltage Transmit and Low-Voltage Isolation * Medical/Industrial Imaging * Ultrasound

* Low Power: Low Impedance (5Ω) with 1.5mA Bias Current Only

* Low Noise < 0.5nV/√Hz (typ) with 1.5mA Bias Current Only

* Wide -3dB Bandwidth 65MHz (typ)

* Easy Programming with SPI Interface

* High Density (8 Channels per Package)

* Grass-Clipping Diodes with Low-Voltage Isolation (MAX4936/MAX4938)

* Output Clamp Diodes for Receiver Protection (MAX4936/MAX4937)

* Global Shutdown Control (CLR)

* Each T/R Switch Can Be Individually Programmed On or Off

* Low-Voltage Receive Path with High-Voltage Protection

* Space-Saving, 5mm x 11mm, 56-Pin TQFN Package