Ismail H. Oguzman

A fail-safe ESD protection circuit with 230 fF linear capacitance for high-speed/high-precision 0.18 /spl mu/m CMOS I/O application

Integration of RF/analog and digital circuitry imposes great challenges on Electro-Static-Discharge (ESD) circuit design. Substrate noise coupling through parasitic ESD capacitance degrades the RF/analog input signal, due to both ESD capacitance value and its non-linearity. This paper presents a new 4 kV fail-safe ESD structure, which uses a forward-biased diode to isolate the high capacitance node and uses both N/P junctions and P/N junctions to compensate voltage dependent capacitance. A 230 fF, linear ESD capacitance is achieved without sacrificing the protection capability. This ESD structure uses substrate pumping and sequential booting to trigger as an effective clamp. It also represents total protection including a CDM clamp.

A 180-V pp Integrated Linear Amplifier for Ultrasonic Imaging Applications in a High-Voltage CMOS SOI Technology

This brief presents a monolithically integrated fully differential linear HV amplifier as the driver of an ultrasonic transducer. The linear amplifier is capable of transmitting HV arbitrary signals with a very low harmonic distortion, which is suitable for tissue harmonic imaging and other ultrasonic modes for enhanced imaging quality. The amplifier is designed and implemented using the 0.7- μm CMOS silicon-on-insulator process with 120-V devices. The amplifier, when driving a load of 300 pF in parallel with 100 Ω, is capable of transmitting a sine-wave signal with a frequency of up to 4.4 MHz, a maximum signal swing of 180 Vpp, and a second-order harmonic distortion (HD2) of -56 dBc but only dissipating an average power of 62 mW with a 0.1% duty cycle.

A digital-feedback pre-distortion technique for integrated high-voltage ultrasound transmitting power amplifiers

Ultrasound systems require high-voltage (HV) transmitters to excite the transducers. Compared to digital pulsers, class-AB power amplifiers have many advantages, such as lower harmonics and the capability of generating complex arbitrary waveforms for Coded-Excitation Mode and other advanced ultrasound imaging modes. However, the need to suppress cross-over distortion and achieve high slew-rate usually requires large biasing current. This significantly degrades the power efficiency of the system, limiting the number of integrated transmitter channels in a single package. This paper presents a digital feedback pre-distortion system for ultrasound HV class-AB power amplifier (PA) to reduce the harmonic distortions while at the same time improving the power efficiency. The proposed system searches the error coefficients of the output feedback signal using the least-mean-square (LMS) algorithm, and stores the error data in the look-up table (LUT) memory. On the next cycle the errors are used to equalize the ideal input waveforms with the negative harmonic components to cancel the amplifiers non-linear response. The proposed algorithm applies to both constant magnitude sine-wave and the Morlet Wavelet. The measurement results show that the proposed system reduces the second-order harmonics (HD2) in the output sine-wave signals by 20 dB and the third-order harmonics (HD3) by 15 dB, while increasing the amplifier power efficiency by 18%. The proposed technique reduces the nonlinear higher-order effects of the PA to improve the ultrasound transmitting signal fidelity, which relieving the requirement on amplifier biasing current and supply voltage headroom.