US 5,632,019 A · Output buffer with digitally controlled power handling characteristics

Abstract

A programmable output buffer has source/sink characteristics that may be programmed to match the capacitive load to be driven. The programmable output buffer comprises a plurality of individually-enableable unit buffers, and a programmable unit buffer driver control logic. By programming the control logic to enable only such unit buffers whose current handling contributions are necessary to drive the output buffer load capacitance, current spiking can be minimized. The unit buffers preferably are scaled so each can source or sink a different magnitude current relative to the other unit buffers, a range of output buffer current may be programmed in discrete current steps. The control logic preferably includes elements that delay delivery of an enabling signal to various of the unit buffers. In a cascade-up mode, the control logic sequentially delays enabling signals so that various of the required unit buffers are enabled sequentially, to minimize problems associated with current spiking. In a cascade-down mode, the unit buffers are simultaneously enabled but are sequentially disabled. A mode encompassing cascade-up and cascade-down mode operation is provided, as is a mode wherein the sequence of cascade-on and/or cascade-off enabling signals is retriggered for every data change. This mode permits changing data in the buffer without creating current spikes that would result if the data were changed while the unit buffers were enabled.

Claims20

Dependent claims

An output buffer with programmable output characteristics for interfacing with a hard disc drive unit, comprising:

a first enableable unit buffer;
a second enableable unit buffer;
wherein each said enableable unit buffer has an input node, an output node, and an enabling node, each said enableable unit buffer input node being coupled together to form an output buffer input node that is coupleable to a data input signal, and each said unit enableable buffer output node being coupled together to form an output buffer output node providing a data output signal coupleable to a load impedance;
wherein each said enableable unit buffer can source and sink at least a portion of output current sourced and sunk by said output buffer;
and
computer implemented program means for providing a first enable control signal, coupled to the enabling node on said first enableable unit buffer, and further providing a second enable control signal coupled to the enabling node on said second enableable unit buffer;
wherein said program means causes chosen combinations of said first enableable unit buffer and said second enableable unit buffer to be enabled to vary at least one output characteristic of said output buffer selected from the group consisting of (a) minimizing operating power consumed by said output buffer, (b) reducing current spiking associated with said output buffer, (c) reducing noise radiation associated with said output buffer, (d) reducing voltage overshoot/undershoot associated with said data output signal provided by said output buffer, (e) reducing crosstalk associated with said output buffer, and (f) improving transmission line characteristics associated with said output buffer.

4 more elements

A method of providing a hard disc drive unit interfacing output buffer with programmable output characteristics, the method comprising the following steps:

providing a first enableable unit buffer and a second enableable unit buffer;
wherein each said enableable unit buffer has an input node, an output node, and an enabling node, each said enableable unit buffer input node being coupled together to form an output buffer input node that is coupleable to a data input signal, and each said enableable unit buffer output node being coupled together to form an output buffer output node providing a data output signal coupleable to a load impedance;
wherein each said enableable unit buffer can source and sink at least a portion of output current sourced and sunk by said output buffer;
and
providing program means for providing a first enable control signal, coupled to the enabling node on said first enableable unit buffer, and further providing a second enable control signal coupled to the enabling node on said second enableable unit buffer;
wherein said program means causes chosen combinations of said first enableable unit buffer and said second enableable unit buffer to be enabled to vary at least one output characteristic of said output buffer selected from the group consisting of (a) minimizing operating power consumed by said output buffer, (b) reducing current spiking associated with said output buffer, (c) reducing noise radiation associated with said output buffer, (d) reducing voltage overshoot/undershoot associated with said data output signal provided by said output buffer, (e) reducing crosstalk associated with said output buffer, and (f) improving transmission line characteristics associated with said output buffer.

3 more elements

Dependencies are inferred from the claim text.

Output buffer with digitally controlled power handling characteristics

Life of this patent

Output buffer with digitally controlled power handling characteristics

Life of this patent

Abstract

Claims20