John Contreras

Modeling of a Disk Drive's Front-End Channel Path

A system approach for designing the channel path of disk drives is required for achieving high data rates and maintaining data integrity. The channel path includes electronics, electrical interconnects, and the read/write heads. The signal transfer through electrical interconnects is affected by its physical components that create the losses and the termination effects. From electromagnetic analysis or measurements, s-parameters are obtained for analyzing signal transfer and crosstalk. Using these s-parameters, chain type matrices can be created to apply an efficient system analysis of the signal transfer. This type of system analysis can be used to produce frequency and time domain response of the complete channel path: read/write transducers, suspension interconnect, read/write IC, flex interconnect, and channel IC

Recording Front-End Systems Analysis

As data rates continue to increase, front-end design techniques and analysis must evolve in order to manage the transmission line effects and the parasitic effects of the transducer, electronics, and electrical interconnect. In addition, the complete write process contains linear and non-linear effects, which requires write signal wave-shaping for optimum performance. Data signal fidelity is maintained by proper termination at the read/write integrated circuit (IC), which is dependent on the read/write transducers impedance range. For writing, transmission-line termination techniques along with the write-driver electronics are utilized to induce the required overshoot for transitions in the write current waveform. For reading, the key aspects of signal-to-noise ratio (SNR) and bandwidth are the parasitic components at the read transducer and the input at the read amplifier. The Noise Figure (NF) of the front-end system can be modeled to include the parasitic effects along with the transmission losses of the interconnect. Here, we expound on design techniques and component values for the front-end system.

Thermal Transient Response of Electrical Self Heating in Current-in-Plane Magnetoresistive Heads

This paper presents an electrothermal model using dynamic resistance thermometry to determine the temperature rise of a current-in-plane GMR sensor in response to imperfect electrical bias (i.e., a DC bias with transients). Measurement and simulation results are given for two different GMR heads (width 500 and 150 nm, respectively). The smaller of the heads is shown to have a virtual instantaneous thermal response (0.2 ns) to transients. Such transients in the bias can, therefore, endanger the read stability and expected lifetime for todays small heads. It is also shown that the peak in the sensor temperature rise is much larger than the sum of the temperature rise due to the bias current and due to the transient current determined separately

Electromagnetic Modeling of a Disk Drive¢??s Front-End Channel Path

Three-dimensional electromagnetic modeling is employed to analyze the signal transfer and crosstalk. The analysis results, from the physical structure, produce a set of s-parameters for the signal path. These s-parameters include the effects of the high-frequency signal losses from the suspension interconnect, such as skin effect and dielectric losses.