Low Power Design interview questions

1. A.switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control
2. B.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
3. C.dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage
4. D.IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent

Answer + AI explanation with Pro

1. A.DVFS
2. B.Clock gating
3. C.Isolation cells
4. D.Retention registers

Answer + AI explanation with Pro

1. A.Clock gating — gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic
2. B.Clock gating — disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
3. C.Clock gating — cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else
4. D.Clock gating — switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control

Answer + AI explanation with Pro

1. A.IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent
2. B.cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else
3. C.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
4. D.gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic

Answer + AI explanation with Pro

1. A.UPF
2. B.Isolation cells
3. C.Clock gating
4. D.Multi-Vt libraries

Answer + AI explanation with Pro

1. A.Multi-Vt libraries — flip-flops with a shadow latch on an always-on supply that save state before power-down and restore it on wake-up, avoiding a full re-initialisation
2. B.Multi-Vt libraries — IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent
3. C.Multi-Vt libraries — simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon
4. D.Multi-Vt libraries — cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else

Answer + AI explanation with Pro

1. A.cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else
2. B.switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control
3. C.simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon
4. D.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total

Answer + AI explanation with Pro

1. A.Level shifters
2. B.Multi-Vt libraries
3. C.DVFS
4. D.Power gating

Answer + AI explanation with Pro

1. A.Power gating — dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage
2. B.Power gating — cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges
3. C.Power gating — simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon
4. D.Power gating — switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control

Answer + AI explanation with Pro

1. A.simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon
2. B.dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage
3. C.cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else
4. D.IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent

Answer + AI explanation with Pro

1. A.Retention registers
2. B.DVFS
3. C.UPF
4. D.Power gating

Answer + AI explanation with Pro

1. A.UPF — disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
2. B.UPF — cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges
3. C.UPF — gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic
4. D.UPF — IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent

Answer + AI explanation with Pro

1. A.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
2. B.gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic
3. C.IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent
4. D.simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon

Answer + AI explanation with Pro

1. A.UPF
2. B.Isolation cells
3. C.Power gating
4. D.Multi-Vt libraries

Answer + AI explanation with Pro

1. A.Isolation cells — cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges
2. B.Isolation cells — dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage
3. C.Isolation cells — IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent
4. D.Isolation cells — gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic

Answer + AI explanation with Pro

1. A.flip-flops with a shadow latch on an always-on supply that save state before power-down and restore it on wake-up, avoiding a full re-initialisation
2. B.simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon
3. C.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
4. D.switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control

Answer + AI explanation with Pro

1. A.UPF
2. B.Clock gating
3. C.Retention registers
4. D.Power-aware simulation

Answer + AI explanation with Pro

1. A.Retention registers — gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic
2. B.Retention registers — dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage
3. C.Retention registers — flip-flops with a shadow latch on an always-on supply that save state before power-down and restore it on wake-up, avoiding a full re-initialisation
4. D.Retention registers — cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges

Answer + AI explanation with Pro

1. A.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
2. B.cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges
3. C.switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control
4. D.flip-flops with a shadow latch on an always-on supply that save state before power-down and restore it on wake-up, avoiding a full re-initialisation

Answer + AI explanation with Pro

1. A.UPF
2. B.Level shifters
3. C.Isolation cells
4. D.Clock gating

Answer + AI explanation with Pro

1. A.Level shifters — cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges
2. B.Level shifters — cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else
3. C.Level shifters — disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
4. D.Level shifters — IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent

Answer + AI explanation with Pro

1. A.IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent
2. B.switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control
3. C.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
4. D.dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage

Answer + AI explanation with Pro

1. A.Multi-Vt libraries
2. B.Level shifters
3. C.DVFS
4. D.Power-aware simulation

Answer + AI explanation with Pro

1. A.DVFS — dynamic voltage and frequency scaling that lowers supply and clock together when demand drops, exploiting the quadratic dependence of switching power on voltage
2. B.DVFS — switching off supply to idle blocks with header or footer sleep transistors, nearly eliminating leakage but requiring wake-up time and rush-current control
3. C.DVFS — flip-flops with a shadow latch on an always-on supply that save state before power-down and restore it on wake-up, avoiding a full re-initialisation
4. D.DVFS — IEEE 1801 Unified Power Format describing power domains, supply nets, switches, isolation and retention so tools implement and verify the power intent

Answer + AI explanation with Pro

1. A.disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total
2. B.cells with low, standard and high threshold voltage; low-Vt is fast but leaky, so it is used only on critical paths and high-Vt everywhere else
3. C.gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic
4. D.simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon

Answer + AI explanation with Pro

1. A.Clock gating
2. B.Power-aware simulation
3. C.Retention registers
4. D.Level shifters

Answer + AI explanation with Pro

1. A.Power-aware simulation — gates at the outputs of a powered-down domain clamping signals to a known value so floating inputs do not corrupt the always-on logic
2. B.Power-aware simulation — simulation reading the UPF so powered-down logic is corrupted to X and isolation and retention behaviour is checked, catching sequencing bugs before silicon
3. C.Power-aware simulation — cells placed on nets crossing between voltage domains so a lower-voltage driver correctly switches a higher-voltage receiver without leakage or slow edges
4. D.Power-aware simulation — disabling the clock to idle registers with an integrated clock-gating cell, cutting dynamic power since clock nets often burn 30–40% of the total

Answer + AI explanation with Pro