摘要:
A voltage translator uses an n-channel translator transistor to translate an input voltage at its drain to an output voltage at its source. The gate and substrate of the translator transistor are each biased by charge pumps. A reference transistor is also biased by the charge pumps. A reference input voltage is translated to a reference output voltage by the reference transistor. The reference output voltage is compared to a target output voltage by comparators. When the reference output voltage is below the target, the gate charge pump is turned on, raising the gate voltage to both the reference and translator transistors. The higher gate voltage VGATE raises the output voltage VOUT since VOUT=VGATE-VT for a transistor in saturation. When the reference output voltage is above the target, the substrate charge pump is turned on, pulling the substrate bias voltage below ground. The body effect causes the transistor threshold VT to increase as the substrate is pumped. The higher threshold lowers the output voltage. Once the reference output voltage reaches the target, the charge pumps turn off. The input voltage can toggle high and low since the reference transistor sets the gate and substrate voltages.
摘要:
A CMOS output buffer has as pull-downs a smaller driver transistor and a larger driver transistor. Both transistors drive the output low in parallel initially during a voltage transition, but the larger transistor is disabled for the remainder of the output voltage swing when reflections and ringing occur. A pulse is generated by a transition detector when an input to the output buffer transitions low. The pulse generated disables the larger driver for a short period of time but later re-enables the driver. Thus the large driver remains on after the switching is complete, providing large IOH and IOL static currents. The pulse is long enough to keep the large driver disabled while reflections are received and ringing occurs after the voltage transition. A Resistor in series with the smaller driver transistor absorbs these reflections. The output impedance is pulsed to the higher impedance of the first stage when ringing occurs at the end of the voltage transition, but after the pulse ends, the lower impedance of the large driver is seen. Pulses are generated when any neighboring output changes. The pulse generated is sent to all neighboring output buffers to disable their large drivers when noise in injected into the power or ground supplies.
摘要:
A circuit for use in conjunction with a portion of a core of an integrated circuit, for shifting a signal from a first voltage level to a second voltage level, wherein the circuit is formed using the same process type transistors (i.e., low voltage transistors) as are used in the core of the integrated circuit.
摘要:
A cross-pin electro-static-discharge (ESD) protection device protects against ESD zaps between two I/O pins. Pin A is connected to a drain of a bus-switch transistor and pin B is connected to the transistor's source. An ESD protection device on pin A has an n-channel shunting transistor to an internal ground bus. The gate of the shunting transistor is a cross-gate node that is capacitivly coupled to pin A, and has a leaker resistor to ground. An n-channel cross-grounding transistor has its gate connected to the same cross-gate node, but it connects the internal ground bus to pin B, which is grounded in the pin-to-pin ESD test. An ESD pulse on pin A drives the cross-gate node high, turning on both the shunting transistor and the cross-grounding transistor. The floating internal ground bus is connected to ground by pin B, grounding the substrate of the bus-switch transistor to prevent its turn-on.
摘要:
Large output driver transistors are used to shunt electro-static-discharge (ESD) pulses. ESD pulses are capacitivly coupled to the gates of the large driver transistors by R-C networks. The capacitive coupling causes a gate-to-source voltage to exceed the transistor threshold, turning on the large driver transistor to shunt the ESD current. Transistor switches are inserted into the R-C networks. These transistor switches disconnect the R-C networks during normal operation, and ensure that the R-C networks couple the I/O pad to the gates of the output driver transistors only when power is turned off. Since ESD events normally occur when power is disconnected, such as during handling by a person or machine, the ESD protection is only needed when power is off. Thus an active ESD-protection device can be disabled during normal powered operation of the IC. A feedback circuit detects power and biases the gates of the transistor switches.
摘要:
A differential buffer/driver has a switch network that connects an IOH current source to a differential output to be drive high, and connects an IOL current source to the other differential output to be driven low. Each output can be connected to a pull-down boost current sink. A boost pulse momentarily connects a boost current sink to the differential output being driven low. The differential buffer generates a pair of boost pulses to activate the boost current for either differential output. One boost pulse is activated when one differential output is driven low, while the other boost pulse is activated when the other differential output is driven low.
摘要:
A voltage translator programmably converts signals generated from a first power-supply voltage to a second power-supply voltage, or vice-versa. In response to control signals, bootstrap switches connect either the first or second power supply to a first internal supply, and either the second or first power supply to a second internal supply. A pair of inverters are sourced by the first power supply and generate true and complement data signals. Cross-coupled p-channel load transistors are sourced by the second internal power supply. A differential pair of n-channel transistors have drains connected to the drains of the load transistors, and gates driven by the true and complement data signals. The bootstrap switches use boosted signals above the power-supply voltages to programmably connect full-voltage power supplies to the internal supplies.
摘要:
A clock driver for an integrated circuit reduces electro-magnetic interference (EMI) induced in nearby metal traces yet also reduces jitter due to noise at the switching threshold. A weak driver using small n-channel and p-channel transistors initially drives the clock line. Then a pulse generator produces a short pulse to a gate of a large driver transistor. The large driver transistor is pulsed on for a very short period of time. The large driver transistor is turned off by the end of the pulse before the clock line completes its transition. The weak driver then finishes the clock-line transition. Since only the weak driver is on during the start and end of the transition, a slow voltage-slew rate occurs at the beginning and end of the transition. The large driver transistor is on only in the middle of the transition, producing a fast voltage-slew rate in the middle. A triple-slope waveform results. Since a fast voltage-slew occurs in the middle of the transition near the receiver's switching threshold, clock jitter due to supply noise is reduced. EMI is reduced because the average slew rate is reduced.
摘要:
According to one embodiment, a phase-locked loop (PLL) device includes test circuitry for entering/exiting a test mode upon receiving a particular pulse train at a reference clock input of the PLL. In addition, exemplary methods are provided herein for entering a test mode and detecting loop filter leakage within the PLL. The methods described herein are performed without the use of a dedicated test pin.
摘要:
A bus-switch transistor connects two I/O pins when an enable signal on its gate is activated. Each pin has an electro-static-discharge (ESD) protection devices. When the internal ground and the enable are floating, and an ESD pulse is applied between the two pins, an isolation circuit couples part of the ESD pulse to the gate of the bus-switch transistor, keeping the transistor turned off. This forces the ESD pulse to travel through the ESD protection devices, preventing damage to the bus-switch transistor. The isolation circuit has a capacitor between a pin and the gate of a coupling transistor. The capacitor couples the ESD pulse to the gate of the coupling transistor. The coupling transistor turns on, connecting the pin to the gate of a grounding transistor. The grounding transistor then turns on, connecting the gate of the bus-switch transistor to the other pin, which is grounded during the ESD test.