Over-the-rail write driver for magnetic storage systems

A write circuit for generating a write current pulse for use by a magnetic write head, the write circuit comprising:

• first and second pull-up write drivers, each of the first and second pull-up write drivers being adapted for connection with a first voltage supply rail of the write circuit, the first pull-up write driver having a first output coupled with a first node of the magnetic write head, the second pull-up write driver having a second output coupled with a second node of the magnetic write head;
• and
• first and second pull-down write drivers, each of the first and second pull-down write drivers being adapted for connection with a second voltage supply rail of the write circuit, the first pull-down write driver having a third output coupled with the first node of the magnetic write head, the second pull-down write driver having a fourth output coupled with the second node of the magnetic write head;
• each of the respective write drivers comprising:
• an output stage adapted for connection with the magnetic write head;
• a charge storage circuit connected with the output stage, the charge storage circuit being operative in a first mode to store a prescribed charge and being operative in a second mode to transfer at least a portion of the charge stored therein to the output stage to thereby enable an output voltage level of the output stage to extend beyond a corresponding one of the first and second voltage supply rails of the write circuit;
• and
• a control circuit operative to generate at least one control signal for selectively controlling a mode of operation of the charge storage circuit;
• wherein the charge storage circuit in each of at least a subset of the respective write drivers comprises:
• a capacitive element having a first node connected with the magnetic write head through the output stage;
• a diode adapted for connection between the first node of the capacitive element and a corresponding one of the first and second voltage supply rails;
• and
• a current source coupled with a second node of the capacitive element and operative to supply a charging current to the capacitive element during the first mode.

A data storage and retrieval system, comprising:

• a magnetic write head operative to store binary encoded information as magnetic flux patterns imparted on a magnetic storage medium as the medium passes by the write head as a function of a write current pulse supplied to the write head;
• and
• a write circuit for generating the write current pulse, the write circuit comprising:
• first and second pull-up write drivers, each of the first and second pull-up write drivers being adapted for connection with a first voltage supply rail of the write circuit, the first pull-up write driver having a first output coupled with a first node of the magnetic write head, the second pull-up write driver having a second output coupled with a second node of the magnetic write head;
• and
• first and second pull-down write drivers, each of the first and second pull-down write drivers being adapted for connection with a second voltage supply rail of the write circuit, the first pull-down write driver having a third output coupled with the first node of the magnetic write head, the second pull-down write driver having a fourth output coupled with the second node of the magnetic write head;
• each of the respective write drivers comprising:
• an output stage adapted for connection with the magnetic write head;
• a charge storage circuit connected with the output stage, the charge storage circuit being operative in a first mode to store a prescribed charge and being operative in a second mode to transfer at least a portion of the charge stored therein to the output stage to thereby enable an output voltage level of the output stage to extend beyond a corresponding one of the first and second voltage supply rails of the write circuit;
• and
• a control circuit operative to generate at least one control signal for selectively controlling a mode of operation of the charge storage circuit;
• wherein the charge storage circuit in each of at least a subset of the respective write drivers comprises:
• a capacitive element having a first node connected with the magnetic write head through the output stage;
• a diode adapted for connection between the first node of the capacitive element and a corresponding one of the first and second voltage supply rails;
• and
• a current source coupled with a second node of the capacitive element and operative to supply a charging current to the capacitive element during the first mode.