• Multiple-level ultrasound pulser
• Fast switching current source for push-pull topology
• 250MHz maximum frequency, 4.0ns input to output delay
• 15 independent programmable output level registers
• Pulse amplitude modulation (PAM) with 8-bit resolution
• 8-bit apodization DAC for peak output current via SPI
• Very low second order harmonic distortion
• Picoseconds time-jitter from input to output
• Fast SPI write and read-back of level & DAC registers
• +5.0V power supply, 2.5V CMOS logic interface
• Drives DN2625 MOSFETs output up to 230VP-P
• Programmable aperture windowing

The MD2134 is a high-speed source driver for use in a pulsed current waveform generator. This programmable, fast, arbitrary current level driver is designed for medical ultrasound imaging beamforming applications. It also can be used in HIFU, NDT ultrasound and other instrument applications. The MD2134 consists of CMOS digital logic input circuits, an eight-bit current DAC for aperture weighting amplitude control, and a programmable 15-level pulse amplitude modulation (PAM) current-source that does not include a zero level. The fast current sources are constructed with current-switch array, controlled by the LV0~LV15 level-register as the waveform data points. Four logic inputs M[3:0] are used for transmit data level selecting, as well as the transmitting timing control pins. Each level can be programmed to a resolution of +/-127 including zero (8-bit) in addition to an 8-bit SPI apodization DAC. The outputs PA and PB are controlled by M[3:0] pins directly, as well as the polarity-flip bit S1 in the SPI register. The high-speed SPI interface will achieve per-scan-line fast data updating for dynamically changing delay time, weighting and waveforms. The MD2134 outputs are designed to drive two very low-threshold, high-voltage depletion N-MOSFETs, such as DN2625s, as source drivers. The two DN2625 drains are connected to a center-tap RF pulse transformer. The transformer’s secondary output connects to a cable and piezoelectric or capacitive transducer as a load with a good impedance match.