DESCRIPTION The L6326 is a two channel BICMOS monolithic integrated circuit GMR pre-amplifier designed for use with four-terminal magneto-resistive (AMR and GMR heads) read/inductive write heads. The device consists of a voltage sense current bias or voltage bias (selectable), single ended input/ true differential output (RDX, RDY), low-noise high bandwidth read amplifier and includes fast current switching write drivers which support data rates up to 500 Mb/s with 90nH write heads. ■ Power Supplies +5Vdc, +8Vdc ■ Current bias or voltage bias (selectable) / Voltage sense architecture ■ Single ended read input ■ 24 pin TSSOP package, two channels ■ External Resistor for read and write currents or trimmed internal resistor available (serial port selectable) ■ Read channel -3dB bandwidth > 300MHz (Rmr=60 ohms, no interconnect) ■ Input equivalent preamplifier voltage noise 0.5nV/rtHz typ ■ Input equivalent MR bias current noise 10pA/rtHz typ ■ MR bias current programmable (5 bit DAC) 1.8- 8mA (GMR range), 3.8-10mA (AMR range) ■ MR bias voltage programmable (5 bit DAC) 100- 460mV (GMR range), 220-580mV (AMR range) ■ Programmable gain (100V and 150V) ■ Write frequency up to 250MHz (Lh=90nH,R=15 ohms, Ch=2pF, VDD=8V) ■ Rise/Fall time <0.7ns (Iw =40mA 0-pk, Lh=90nH, Rh=15 ohms, Ch=2pF, VDD=8V) ■ Write current programmable (5 bit DAC) 15-60mA ■ Overshoot control 3 bit resolution (+1 bit for range) ■ Bi-directional 16-bit TTLs Serial interface for head selection, read/write currents selection, chip parameters modification, chip enable, vendor code and fault status read back registers ■ 2-wire mode selection (R/W, MRR) ■ Bank write feature for servo write ■ Digital buffered head voltage DBHV / Analog buffered head voltage ABHV pin (gain 5) ■ Thermal asperity detection with adjustable sensitivity level (6 bit DAC) ■ Thermal asperity correction ■ Read head open/short detection ■ Low supply detect and temperature monitoring (high temperature warning and Analog Temperature ■ Diode Voltage measurement) ■ Low write frequency detection ■ WRITE to READ fast recovery 250ns (same head, including 150ns blanking period) ■ GMR Low-Bias in WRITE mode with fast recovery to READ mode bias (250ns) ■ Head-to-head switch in READ mode - 10µs (typ) ■ Head and MR bias current switching transient current head protection ■ READ-to-WRITE switching 30ns (same head) ■ Programmable read bias during write and bank write operation ■ ESD diodes for GMR protections ■ Differential Write Driver to minimize coupling to GMR element
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