High-precision voltage dependent timing delay circuit
First Claim
1. A timing delay circuit which comprises delay means (1) for providing an output signal (3) in response to an input signal (2), where said output signal is delayed with respect to said input signal, said delay varying with a supply voltage (Vdd) by which said circuit is powered;
- and circuit means (78) with a switching threshold (21) which are connected to said output of said delay means for receiving said output signal (3), said timing delay circuit characterized by switching means (14, 34, 43,
70) for providing a current sink element (NFET 14, 34, or
70) or a current source element (PFET
43) coupled to the output of the delay means (1), said current sink element sinking current from said output signal (3) upon a rising edge of said output signal (3) of said delay means (1) and said current source element sourcing current to said output signal (3) of said delay means upon a falling edge of said output signal (3) of said delay means (1), said switching means being enabled by an adjustable control voltage (71) which varies in proportion to said supply voltage, said switching means being enabled if said supply voltage exceeds a minimum value and said switching means being disabled if said supply voltage is below said minimum value , said enabled switching means further delaying the output signal (3) of the delay means by increasing the time required for the rising or falling edge of said output signal to respectively rise or fall to the switching threshold of the circuit means.
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Accused Products
Abstract
For high-speed single-ended sensing of the small signal delivered from a (static) RAM or ROM cell, a voltage dependent timing delay circuit is disclosed which prevents early triggering of the set signal of the sense amplifier (SSA 66) when applying a high voltage screen test (i.e. 1.5 times VDD) to the cell. The timing of the SSA signal is achieved by a high precision delay chain comprising inverters, which is loaded by a voltage dependent current sink (70) coupled to the output of the chain. The inverter delay chain controls the input (SE0) for a driver for the SSA line (66). The current sink may be a pull down NFET (70) which is only activated when the supply voltage is above a determined switching threshold therefor. The gate voltage of the NFET is controlled by a bias control circuit (72) in such a manner that during operation at typical voltage levels, the NFET is deactivated, whereas at higher operating voltage levels (such as 1.5 * VDD) the NFET is turned on, thereby sinking current from the input (SE0) to the driver for the SSA line. The SSA signal is consequently delayed preventing the early triggering thereof.
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Citations
17 Claims
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1. A timing delay circuit which comprises delay means (1) for providing an output signal (3) in response to an input signal (2), where said output signal is delayed with respect to said input signal, said delay varying with a supply voltage (Vdd) by which said circuit is powered;
- and circuit means (78) with a switching threshold (21) which are connected to said output of said delay means for receiving said output signal (3), said timing delay circuit characterized by switching means (14, 34, 43,
70) for providing a current sink element (NFET 14, 34, or
70) or a current source element (PFET
43) coupled to the output of the delay means (1), said current sink element sinking current from said output signal (3) upon a rising edge of said output signal (3) of said delay means (1) and said current source element sourcing current to said output signal (3) of said delay means upon a falling edge of said output signal (3) of said delay means (1), said switching means being enabled by an adjustable control voltage (71) which varies in proportion to said supply voltage, said switching means being enabled if said supply voltage exceeds a minimum value and said switching means being disabled if said supply voltage is below said minimum value , said enabled switching means further delaying the output signal (3) of the delay means by increasing the time required for the rising or falling edge of said output signal to respectively rise or fall to the switching threshold of the circuit means. - View Dependent Claims (2, 7, 8)
- and circuit means (78) with a switching threshold (21) which are connected to said output of said delay means for receiving said output signal (3), said timing delay circuit characterized by switching means (14, 34, 43,
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3. A timing delay circuit which comprises delay means (1) for providing an output signal (3) in response to an input signal (2), where said output signal is delayed with respect to said input signal, said delay varying with a supply voltage (Vdd) by which said circuit is powered;
- and circuit means (78) with a switching threshold (21) which are connected to said output of said delay means for receiving said output signal (3), said timing delay circuit characterized by switching means (14, 34, 43,
70) for providing a current mink element (NFET 14, 34, or
70) or a current source element (pFET
43) coupled to the output of the delay means (1), said current sink element sinking current from said output signal (3) upon a rising edge of said output signal (3) of said delay means (1) and said current source element sourcing current to said output signal (3) of said delay means upon a falling edge of said output signal (3) of said delay means (1), said switching means being enabled by an adjustable control voltage (71) which is dependent upon said supply voltage, said enabled switching means further delaying said output signal (3) of said delay means, and wherein said timing delay circuit further includes clock means (82) for providing a clock signal to said switching means for controlling the level of the adjustable control voltage of said switching means. - View Dependent Claims (4, 5, 6, 11, 12, 13, 14, 15, 16, 17)
- and circuit means (78) with a switching threshold (21) which are connected to said output of said delay means for receiving said output signal (3), said timing delay circuit characterized by switching means (14, 34, 43,
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9. In a timing delay circuit comprising
delay means (1) for providing an output signal (3) in response to an input signal (2), where said output signal is delayed with respect to said input signal, said delay varying with a supply voltage (Vdd) by which said circuit is powered; -
circuit means (78) with a switching threshold (21) which are connected to said output of said delay means; and switching means (14, 34, 43,
70) for providing a current sink/source dependent on a rising/falling edge of said output signal, which is connected to said output of said delay means, and which is switched by a control voltage (71) dependent on said supply voltage;a method for precisely adjusting said timing delay dependent on said supply voltage, characterized by the steps of; determining a threshold voltage for said switching means; and switching said switching means dependent on whether said supply voltage exceeds a minimum value and whether said control voltage becomes larger than said threshold voltage (FIG.
3).
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10. In a timing delay circuit comprising
delay means (1) for providing an output signal (3) in response to an input signal (2), where said output signal is delayed with respect to said input signal, said delay varying with a supply voltage (Vdd) by which said circuit is powered; -
circuit means (78) with a switching threshold (21) which are connected to said output of said delay means; and switching means (14, 34, 43,
70) for providing a current sink/source dependent on a rising/falling edge of said output signal, which is connected to said output of said delay means, and which is switched by a control voltage (71) dependent on said supply voltage;a method for precisely adjusting said timing delay dependent on said supply voltage, characterized by the steps of; determining a threshold voltage for said switching means; and switching said switching means dependent on whether said supply voltage exceeds a minimum value and whether said control voltage becomes smaller than the difference between said supply voltage and said threshold voltage (FIG.
3).
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Specification