VM312

The VM312 has the following features including Low Power Dissipation;Enhanced System Write-to-Read Recovery Time;Power Supply Fault Protection;Schottky Isolated Damping Resistor Standard;Write Unsafe Detection;+5V and +12V Power Supply Requirement;Mirror Image Pinout Options Available;Available in 4, 6, 8, 9 or 10-Channel Options;Pin-compatible with SSI 32R512.

The VM312 is a high-performance, low-power, bipolar mono-lithic read/write preamplifier designed for use with two-terminal thin-film recording heads. It provides write current control, data protection circuitry and a low-noise read preampliPier for ten channels. When unselected, the device enters a sleep mode, with power dissipation reduced to less than 180mW.  Fault protection is provided so that during power supply sequencing the write current generator is disabled. System write-to-read recovery time is minimized by maintaining the read channel common-mode output voltage in the write mode.Very low power dissipation from +5V and +12V supplies is achieved through use of high-speed bipolar processing and innovative circuit design techniques. A 400-ohm damping resistor is included on-chip in series with a Schottky diode pair to maintain high input resistance in the read mode.The VM312 is available in several different packages. Please consult VTC for package availability.

Typically, an adjustment to the calculated head current is required to account for current shunted by the damping resistor.This complication is avoided in the VM312H because the internal damping resistors are series-connected with Schottky diode pairs.In multiple-device applications, a single Rwc resistor may be made common to all devices.Power supply fault protection improves data security by disabling the write current generator during a voltage fault or power supply sequencing. Additionally, the write unsafe detection circuitry will flag any of the conditions listed below as a high level on the open collector output pin,WUS. Two negative transitions on pin WDI, after the fault is corrected, may be required to clear the WUS flag.Write mode configures the VM312 as a current switch and activates the write unsafe (WUS) detection circuitry.  Write current is toggled between the X and Y direction of the selected head on each high-to-low transition on pin WDI (write data in-put).