Abstract: A circuit device having data retention latches utilizes a test interface and system test controller to control one or more components of the circuit device to ensure proper conditions for testing the data retention latches. The data retention latches each include a scan component that is part of a scan chain, a first latching component that is powered in a first voltage domain and a second latching component that is powered in a second voltage domain, where one of the voltage domains can be effectively shut down when the circuit device is placed in a low-voltage mode. The system test controller can control a scan controller used to scan test data in and out of the scan chain. The system test controller further can control a power controller used to manage a power down sequence and a power up sequence so as to ensure that the data retention latches are not placed in spurious states.

Abstract: A flip-flop (10) has a normal mode and a low power mode to save power. The flip-flop (10) has a master latch (14) and a slave latch (20). The slave latch (20) is used to retain the condition of the flip-flop (10) during the low power mode, where power is withdrawn from the master latch (14) but maintained on the slave latch (20). The slave latch (20) may use transistors with lower leakage characteristics than the transistors that make up the master latch (14). These lower leakage characteristics may be achieved by a higher threshold voltage and/or a thicker gate dielectric. Operating speed of the flip-flop (10) is maintained by implementing the slave latch (20) so that no logic gate or switching transistor is in the critical timing path. Instead, the slave latch (20) has an input/output terminal to tap into the signal path between the master latch and an output circuit (22).

Abstract: A flip-flop (10) comprises a first latch circuit (18), a second latch circuit (24), and a third latch circuit (26). The first latch circuit (18) is coupled to receive a clock signal and a first power supply voltage. The second latch circuit (24) is coupled to the first latch circuit (18) and receives the clock signal and the first power supply voltage. Preparatory to entering a low power mode, the third latch circuit (26) receives a second power supply voltage and is coupled to the second latch circuit (24) in response to a power down signal. During the low power mode, the first power supply voltage is removed from the first and second latch circuits (18, 24). When returning to a normal operating mode, the first power supply voltage is provided to the first and second latch circuits (18, 24), and the third latch circuit (26) is coupled to the first latch circuit (18) in response to a power restore signal.

Abstract: Power consumption may be reduced through the use of power gating in which power is removed from circuit blocks or portions of circuit blocks in order to reduce leakage current. One embodiment uses a modified state retention flip-flop capable of retaining state when power is removed or partially removed from the circuit. Another embodiment uses a modified state retention buffer capable of retaining state when power is removed or partially removed from the circuit. The state retention flip-flop and buffer may be used to allow for state retention while still reducing leakage current. Also disclosed are various methods of reducing power and retaining state using, for example, the state retention flip-flops and buffers. For example, software, hardware, or a combination of software and hardware methods may be used to enter a deep sleep or idle mode while retaining state.

Abstract: Power consumption may be reduced through the use of power gating in which power is removed from circuit blocks or portions of circuit blocks in order to reduce leakage current. One embodiment uses a modified state retention flip-flop capable of retaining state when power is removed or partially removed from the circuit. Another embodiment uses a modified state retention buffer capable of retaining state when power is removed or partially removed from the circuit. The state retention flip-flop and buffer may be used to allow for state retention while still reducing leakage current. Also disclosed are various methods of reducing power and retaining state using, for example, the state retention flip-flops and buffers. For example, software, hardware, or a combination of software and hardware methods may be used to enter a deep sleep or idle mode while retaining state.