Method to improve current and slew rate ratio of off-chip drivers
AssigneeInfineon Technologies AG
InventorsThoai Le, George Alexander
Life of this patent
Estimating the term…
Abstract
An off-chip driver (OCD) circuit and technique to reduce skew between rising and falling edges of output signals as process conditions vary are provided. Variations in process conditions may result in stronger or weaker relative current drive between NMOS and PMOS transistors. One or more process-dependent compensating current paths may be added to conventional pull-up and/or pull-down current paths to compensate for process variations by supplementing the current drive of transistors used to charge (PMOS) or discharge (NMOS) an output node of and end driver (e.g., inverter) stage of an OCD.
Claims21
A method for reducing skew between rising and falling data at an output node of an off-chip driver circuit, comprising:
- generating one or more intermediate voltage signals from an input voltage signal applied to an input node of the driver circuit;
- generating an output voltage signal at the output node based on the one or more intermediate voltage signals;
- and
- providing one or more compensating current paths to or from the output node to compensate for differences between a rate at which the output node is charged and a rate at which the output node is discharged, wherein each compensating current path comprises serially coupled transistors of complementary process types.
An off-chip driver circuit, comprising:
- a first stage for generating one or more intermediate voltage signals from an input voltage signal applied to an input node of the first stage;
- a second stage to receive the one or more intermediate voltage signals and, in response, generate, on an output node of the second stage, an output voltage based on the intermediate voltage signal by selectively switching pull-up and pull-down transistors;
- and
- at least one compensating current path between the output node and a supply or ground line to compensate for changes in at least one of a rate at which the output node is charged and a rate at which the output node is discharged, the at least one compensating current path comprising serially coupled transistors of complementary process types.
An off-chip driver circuit, comprising:
- a first stage configured to generate first and second intermediate voltage signals from an input voltage signal applied to an input node of the first stage;
- a second stage configured to generate an output voltage signal at an output node by switching pull-up and pull-down transistors based on the first and second intermediate voltage signals;
- a compensating pull-up current path in parallel with the pull-up transistor, comprising a first PMOS transistor and a first NMOS transistor serially connected between a supply voltage line and the output node;
- and
- a compensating pull-down current path in parallel with the pull-down transistor, comprising a second PMOS transistor and a second NMOS transistor serially connected between the output node and a ground potential line.
An integrated circuit (IC) device, comprising:
- at least one output node for driving a signal onto an external signal line;
- and
- at least one off-chip driver circuit having,
- a first stage for generating one or more intermediate voltage signals from an input voltage signal applied to an input node of the first stage,
- a second stage to receive the one or more intermediate voltage signals and, in response, generate, on an output node of the second stage,
- an output voltage based on the intermediate voltage signal by selectively switching pull-up and pull-down transistors, and
- at least one compensating current path between the output node and a supply or ground line to compensate for changes in at least one of a rate at which the output node is charged and a rate at which the output node is discharged, the at least one compensating current path comprising serially coupled transistors of complementary process types.
Dependencies are inferred from the claim text.