Voltage power switch

Abstract

A voltage power switch includes circuitry configured to output a known voltage. The voltage power switch includes a lock circuit configured to output a known state and a voltage level shifter configured to receive an input, the input being based on the known state output by the lock circuit. The voltage power switch, using an output circuit, is configured to output a known voltage level based on an output of the voltage level shifter, wherein the known voltage is one of a high voltage V.sub.HI for a fuse programing period or a first non-zero intermediate voltage V.sub.MID1 for a non-fuse programming period.

Claims

1. A method for preventing voltage-induced damage to electrical components of a semiconductor device, the method comprising: outputting, by a voltage power switch, a known non-zero intermediate voltage V.sub.MID1 when a state of a digital logic element is a first state; and selectively transitioning the output of the voltage power switch from the known non-zero intermediate voltage V.sub.MID1 to a known high-voltage V.sub.HI during a fuse programming period, in response to the state of the digital logic element transitioning from the first state to a second state.

2. The method of claim 1, further comprising setting the state of the digital logic element to the first state upon the semiconductor device being powered up.

3. The method of claim 2, further comprising preventing the digital logic element from transitioning from the first state to the second state for at least a predetermined number of clock cycles after setting the state of the digital logic element to the first state.

4. The method of claim 1, further comprising preventing the digital logic element from transitioning from the first state to the second state while a state of a lock circuit is a lock state.

5. The method of claim 4, where, when the lock circuit includes N latches cascaded in series, where N is an integer greater than 1, the method further comprises maintaining the N latches in the lock state until receiving N number of clock pulses.

6. The method of claim 5, further comprising setting the lock circuit to the lock state upon the semiconductor device being powered up.

7. The method of claim 1, wherein the digital logic element is an AND gate, the first state is a LOW state, and the second state is a HIGH state.

8. The method of claim 7, further comprising transitioning the AND gate from the LOW state to the HIGH state in response to the AND gate receiving as inputs: (i) a known state output from a lock circuit when the lock circuit transitions from a lock state to an unlock state after receiving at least a predetermined number of clock cycles; (ii) a low voltage V.sub.LO; and (iii) a user-generated signal indicative of a fuse programming request.

9. A voltage power switch for preventing voltage-induced damage to electrical components of a semiconductor device, the voltage power switch comprising: a digital logic element; and an output circuit configured to: output a known non-zero intermediate voltage V.sub.MID1 when a state of the digital logic element is a first state; and selectively transition the output from the known non-zero intermediate voltage V.sub.MID1 to a known high-voltage V.sub.HI during a fuse programming period, in response to the state of the digital logic element transitioning from the first state to a second state.

10. The voltage power switch of claim 9, further comprising a lock circuit configured to set the digital logic element to the first state upon the semiconductor device being powered up.

11. The voltage power switch of claim 10, wherein the lock circuit is configured to prevent the digital logic element from transitioning from the first state to the second state for at least a predetermined number of clock cycles after the digital logic element is set to the first state.

12. The voltage power switch of claim 10, wherein: the lock circuit is configured, when in a lock state, to prevent the digital logic element from transitioning from the first state to the second state; and the lock circuit comprises N latches cascaded in series, where N is an integer greater than 1; and the N latches are configured to remain in a lock state until receiving N number of clock pulses.

13. The voltage power switch of claim 12, further comprising a reset circuit configured to set the lock circuit to the lock state upon the semiconductor device being powered up.

14. The voltage power switch of claim 9, wherein: the digital logic element is an AND gate, the first state is a LOW state, and the second state is a HIGH state; and the AND gate is configured to transition from the LOW state to the HIGH state in response to receiving as inputs: (i) a known state output from a lock circuit when the lock circuit transitions from a lock state to an unlock state after receiving at least a predetermined number of clock cycles; (ii) a low voltage V.sub.LO; and (iii) a user-generated signal indicative of a fuse programming request.

15. A method for preventing voltage-induced damage to electrical components of a semiconductor device, the method comprising: receiving, by a voltage level shifter, an output of a digital logic element; outputting, from the voltage level shifter to an output circuit, a known high-voltage V.sub.HI when the received output of the digital logic element is a first known state output corresponding to a first state of the digital logic element; selectively transitioning the output from the voltage level shifter to the output circuit from the known high-voltage V.sub.HI to a first known non-zero intermediate voltage, in response to the received output of the digital logic element transitioning from the first known state output to a second known state output corresponding to a second state of the digital logic element; and preventing the digital logic element from transitioning from the first state to the second state for at least a predetermined number of clock cycles after the semiconductor device is powered up.

16. The method of claim 15, further comprising: setting the state of the digital logic element to the first state upon the semiconductor device being powered up.

17. The method of claim 15, where, when a lock circuit includes N latches cascaded in series, where N is an integer greater than 1, preventing the digital logic element from transitioning from the first state to the second state for at least the predetermined number of clock cycles after the semiconductor device is powered up comprises preventing the digital logic element from transitioning from the first state to the second state while a state of the lock circuit is a lock state, including maintaining the N latches in the lock state until receiving N number of clock pulses.

18. The method of claim 17, further comprising setting the lock circuit to the lock state upon the semiconductor device being powered up.

19. The method of claim 15, further comprising: outputting, by the output circuit, a second known non-zero intermediate voltage, in response to receiving, by the output circuit from the voltage level shifter, the known high-voltage V.sub.HI; and selectively transitioning, by the output circuit, the output from the second known non-zero intermediate voltage to the known high-voltage V.sub.HI during a fuse programming period, in response to receiving, by the output circuit from the voltage level shifter, the known non-zero intermediate voltage V.sub.MID2.

20. The method of claim 19, wherein the second known non-zero intermediate voltage is output during a non-fuse programming period.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features of the disclosure, its nature and various advantages, will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

(2) FIG. 1 is a block diagram of voltage power switch in accordance with implementations of the subject matter of this disclosure for regulating voltage supplied to an Integrated circuit;

(3) FIG. 2 is a schematic representation of a lock circuit in accordance with implementations of the subject matter of this disclosure;

(4) FIG. 3 is a flowchart illustrating a method of unlocking the lock circuit in accordance with implementations of the subject matter of this disclosure;

(5) FIG. 4 is a schematic representation of a voltage level shifter in accordance with implementations of the subject matter of this disclosure; and

(6) FIG. 5 shows a timing diagram of the various signals in accordance with implementations of the subject matter of this disclosure.

DETAILED DESCRIPTION

(7) Prior to the development of the 5 nm process nodes (e.g., 10 nm process nodes), Integrated circuits (ICs) included transistors that supported higher voltages (e.g., 1.8V). However, advances in semiconductor technologies scaling also have limited the voltages at which the transistors on such devices can operate. For example, the 5 nm process nodes only support devices (e.g., transistors) operating at 1.2V or 1.5V. However, these ICs still require higher voltages (e.g., 1.8V) for fuse programming. Accordingly, there is a need to selectively provide higher voltages for a short duration during a fuse programming mode while outputting a safe voltage during non-fuse programming mode.

(8) The subject matter of this disclosure may be better understood by reference to FIGS. 1-5.

(9) FIG. 1 is a block diagram of a voltage power switch 100 in accordance with implementations of the subject matter of this disclosure for regulating voltage supplied to an Integrated circuit.

(10) Voltage power switch 100 provides a mechanism for selectively providing a known power up state that allows for passing of high voltages during the fuse-programming period without violating any terminal to terminal voltage limits, in accordance with embodiments discussed herein. Specifically, voltage power switch 100 is configured to selectively output a high voltage during a fuse programming period while outputting an intermediate non-zero voltage that is safe for the components of the IC during a non-fuse programming mode.

(11) As illustrated in FIG. 1, voltage power switch 100 includes a lock circuit 102 which includes a power-on-reset generator 108 and power-on-zero latches 104. The lock circuit 102 serves to protect the voltage power switch 100 from outputting a high voltage during a non-fuse programming period as will be described below. Specifically, in one embodiment, lock circuit 102 includes N number of cascaded power-on-zero latches 104, where N is greater than zero. For example, in one embodiment, lock circuit 102 includes four cascaded power-on-zero latches 104 (as shown in the embodiment of FIG. 2). Power-on-reset generator 108 generates a reset pulse (RESETB 106) which forces a known locked state into the N number of power-on-zero latches 104. During the non-fuse programming period, the lock circuit 102 remains in a locked state ensuring that an output logic SYSRDYP 112 from lock circuit 102 remains “0” until all the power-on-zero latches 104 are unlocked. An unlock procedure for unlocking the N number of power-on-zero latches 104 is described below in connection with the discussion of FIG. 3.

(12) By ensuring the output logic SYSRDYP 112 from lock circuit 102 remains “0” until the lock circuit 102 is unlocked, voltage power switch 100 statistically guarantees a known input into the voltage level shifter 122. Specifically, as shown in FIG. 1, lock circuit output SYSRDYP 112 is combined with an unknown input signal SELECTH 114 (often provided by a System-on-Chip logic component) and a low voltage V.sub.LO 116 and fed into an AND gate 118. Accordingly, the input to the voltage level shifter 122 remains a logic “0” until the lock circuit 102 is unlocked by following the unlocking procedure outlined in FIG. 3 (described below). Therefore, lock circuit 102 maintains a known input to the voltage level shifter 122 despite both input signal SELECTH 114 and low voltage V.sub.LO 116 being of unknown values.

(13) The voltage level shifter 122, in response to receiving a “0” input during the non-fuse programming mode (i.e., while the lock circuit 102 remains locked), serves to shift the voltage up to a high voltage V.sub.HI. In another embodiment, the voltage level shifter 122, in response to receiving a “1” input during the non-fuse programming mode (i.e., while the lock circuit 102 remains locked), serves to shift the voltage up to a second intermediate voltage level V.sub.MID2. In an aspect, the second intermediate voltage level V.sub.MID2 is a non-zero voltage that is lower than the first intermediate voltage level V.sub.MID1. In one example where the first intermediate voltage level V.sub.MID1 is 1.2V, the second intermediate voltage level V.sub.MID2 is 0.6V. In an embodiment, voltage level shifter 122 includes a plurality of cascaded voltage level shifters where a first stage voltage level shifter is configured to shift the voltage from a zero voltage to the second intermediate voltage level V.sub.MID2 and a second stage voltage level shifter is configured to shift the voltage from the second intermediate voltage level V.sub.MID2 to the high voltage V.sub.HI. Operation and structure of voltage level shifter 122 is described in greater detail below in connection with the discussion of FIG. 4.

(14) Accordingly, during the non-fuse programming mode, voltage level shifter 122 outputs a known voltage V.sub.HI to gate 124 of an N-channel Field Effect Transistor (NFET) 126 and a P-channel Field Effect Transistor (PFET) 128. Although FIG. 1 shows a single NFET 126 and PFET 128, various implementations can include any number of arrays of such transistor devices. In accordance with an embodiment, when the gate voltage at gate 124 is V.sub.HI, the NFET 126 is turned ON as its gate-source junction is positively biased while the PFET 128 switches OFF. Therefore, a voltage VQPS equal to the first intermediate voltage V.sub.MID1 is output in this configuration. In accordance with embodiments of the subject matter of this disclosure, the first intermediate voltage V.sub.MID1 is less than the high voltage V.sub.HI and is safe for all transistor devices to operate at. Accordingly, in this way, voltage power switch 100 ensures a safe voltage (first intermediate voltage V.sub.MID1) is output during a non-fuse programming period.

(15) Next, operation of the voltage power switch 100 is discussed during a fuse programming period. First, the N number of cascaded power-on-zero latches 104 receive the unlock signal 110 (e.g., a clock pulse) to unlock each of the N number of cascaded power-on-zero latches 104. Specifically, the latches 104 are sequentially unlocked after N number of clock pulses are registered. For example, conventional systems often use a single latch which may erroneously register a clock pulse and unlock therefore resulting in a high voltage being propagated through the semiconductor device. In contrast, methods and systems disclosed herein provide a cascaded structure of the N-number of latches which statistically guarantees that the latches are not unlocked due to a glitch. Once all of the N number of latches 104 are unlocked, lock circuit 102 outputs a “1” at SYSRDYP 112. SYSRDYP 112 is combined with a “HIGH” SELECTH 114 signal (indicative of a fuse programming mode) and a powered on V.sub.LO 116 so that AND gate 118 outputs a “1”. Voltage level shifter 122, in response to receiving a “1” input from AND gate 118, outputs the second intermediate voltage V.sub.MID2. When the gate voltage at gate 124 is the second intermediate voltage V.sub.MID2, PFET 128 is switched ON and only the high voltage V.sub.HI is output at VQPS and is used to program the fuse for a short duration.

(16) Although the above description describes use of a digital logic AND gate, a person skilled in the art will understand that a digital logic NAND gate may be used instead. For example, the output from the lock circuit 102 may be input to an inverter prior to being input into the digital logic NAND gate.

(17) Accordingly, voltage power switch 100 controls the output voltage VQPS such that an output voltage VQPS is a high voltage V.sub.HI when in a fuse programming mode and is a safe first intermediate voltage V.sub.MID1 when in a non-fuse programming mode. Specifically, voltage power switch 100 uses the lock circuit 102 to generate a known input into the voltage level shifter 122, which in turn generates a known output gate voltage. The known output gate voltage at gate 124 is then used to drive the NFET 126 and PFET 128 to output desired voltages VQPS.

(18) FIG. 2 is a schematic representation of a lock circuit 102 in accordance with implementations of the subject matter of this disclosure. As shown in FIG. 2, the lock circuit 102 includes a power-on-reset (POR) pulse generator 202 and N number of latches 202-1, 202-2, 202-3, . . . , 202-N (collectively 204). Although the embodiment illustrated in FIG. 2 shows a total of four latches, a person skilled in the art will understand that any number of latches may be provided to statistically guarantee a locked state until the correct unlock sequence is received. For example, in one embodiment, the lock circuit includes a total of two cascaded latches.

(19) When the IC is powered up initially, POR pulse generator 202 generates a reset signal RST that puts the latches 204 in a locked state. In an embodiment, an external asynchronous reset pulse may be provided to the lock circuit in order to reset the N latches into a locked state. An unlock signal 206 (e.g., a clock signal) unlocks the N latches by propagating N number of pulses through the lock circuit. In an embodiment, the output of the lock circuit SYSRDYP is obtained by combining the output of each of the N latches using a digital logic AND gate. Accordingly, the lock circuit continues to be in a locked state (i.e., the output SYSRDYP continues to be in “LOW” output) until every latch of the N latches is unlocked. Once N number of pulses are registered and the corresponding N latches are unlocked, the output SYSRDYP provides a “HIGH” output. This procedure therefore prevents a false unlocking of the lock circuit. For example, when only a single latch is used in the lock circuit, a glitch may be registered as a clock pulse, thereby unlocking the lock circuit erroneously. As discussed above, such an error would result in a high voltage beyond the safe limits of the semiconductor device being provided for a prolonged duration, thereby damaging the semiconductor device. Accordingly, the additional redundancies provided in the embodiment of FIG. 2 statistically guarantees prevention of such a false unlock.

(20) FIG. 3 is a flowchart illustrating a method of unlocking the lock circuit in accordance with implementations of the subject matter of this disclosure. At 302, as the IC is powered up, the digital logic remains in an unknown state. In other words, the input voltages to the IC are unknown and therefore unsafe for the devices (e.g., various transistors that cannot operate at voltages higher than a predefined safe voltage level) of the IC to operate at. At 304, a power-on-reset (POR) pulse generator generates a pulse as the unknown power supply is being brought up. Alternatively, or in addition to the POR pulse generator, an asynchronous external reset pulse is also generated at 306.

(21) At 308, the POR pulse and/or the external reset pulse force a known locked state into the N latches of the lock circuit. This guarantees that the unknown power supply being brought up does not propagate through the IC until the lock circuit is safely unlocked. At 310, the system determines whether the voltage power switch is unlocked. As discussed above, during initial power-up sequence, the voltage power switch is locked because of the POR pulse and/or the external reset pulse force.

(22) If at 310, it is determined that the voltage power switch is in a locked state (YES at 310), the process proceeds to 312 where the voltage power switch outputs a known safe voltage regardless of the unknown power supply voltage. As discussed above in connection with FIG. 1, while the voltage power switch is locked, the lock circuit output SYSRDYP remains output “LOW” which in turn causes the output of the voltage power switch to be the safe voltage V.sub.MID1. The process then proceeds to 314, where the system determines a valid unlock procedure has been performed. For example, the system determines whether an N number of pulses corresponding to the N latches have been received.

(23) If it is determined that the valid unlock procedure has been performed (YES at 314), the process proceeds to 316 and the voltage power switch is unlocked. At 318, the lock status of the voltage power switch is updated to an unlocked status. If, on the other hand, it is determined that the valid unlock procedure has not been performed (NO at 314), the process proceeds to 320 and the voltage power switch remains in a locked state. The lock status is updated at 318 and the process returns to 310.

(24) If, at 310, it is determined that the voltage power switch is unlocked (NO at 310), the process proceeds to 312 and the system determines whether the voltage power switch is selected. Specifically, as discussed above in connection with FIG. 1, the system determines whether a SELECTH signal is “HIGH” indicating that a fuse is to be programmed. If at 322, the system determines that the voltage power switch has been selected (YES at 322), the process proceeds to 324 and the voltage power switch outputs a known high voltage for fuse programming. If, on the other hand, the system determines that the voltage power switch has not been selected (NO at 322), the process returns to 312 where a known safe voltage is output from the voltage power switch for regular operation of the IC.

(25) Accordingly, the voltage power switch in accordance with implementations of the subject matter of this disclosure discussed above outputs a known high voltage level suitable for fuse programming as well as outputs a known safe voltage suitable for regular operation of the IC.

(26) FIG. 4 is a schematic representation of a voltage level shifter in accordance with implementations of the subject matter of this disclosure. Level shifters enable inputs at a lower voltage to be translated into outputs at a higher voltage. However, the transistors in the level shifter are exposed to the higher voltage and must be able to safely operate at these higher voltages. Since V.sub.HI in this implementation is higher than the voltages at which the transistors can safely operate, the present disclosure as illustrated in FIG. 4 includes two level shifters 402 and 404 placed in series and are setup to operate at safe voltages.

(27) A low input voltage V.sub.LO is input to the first level shifter 402. In conventional level shifters, when the input voltage V.sub.LO is 0V (during device power up), the output voltage becomes unknown and therefore undesirable. However, in the embodiment shown in FIG. 4, when the input voltage V.sub.LO is 0V, a footer transistor N2A is supplied with a gate voltage equal to the voltage V.sub.LO. This causes the transistor N2A to be cut off which in breaks the conduction path to ground VSS. With transistor N2A breaking off the connection to the ground VSS, the voltage at node 406 is forced to increase towards a first intermediate voltage V.sub.MID1. As voltage at node 406 increases towards the first intermediate voltage V.sub.MID1, a transistor N3A is turned ON (primarily due to leakage) thereby bringing a voltage at node 408 down to 0V. Moreover, as the voltage at node 408 approaches 0V, transistor P0A turns ON thereby reinforcing the voltage at node 406 to increase towards the first intermediate voltage V.sub.MID1. The first level shifter 402 is therefore configured to level shift between the first intermediate voltage V.sub.MID1 and a second non-zero intermediate voltage V.sub.MID2. Next, the second level shifter 404 operates in a similar manner as the first level shifter 402 to level shift between the second non-zero intermediate voltage V.sub.MID2 and the high voltage V.sub.HI.

(28) In other words, the first level shifter 402 accepts inputs that operate from a ground voltage VSS (e.g., 0V) to an input low voltage V.sub.LO (e.g., 0.75V). These are translated to an output that operates between VSS (e.g., 0V) and V.sub.MID1 (e.g., 1.2V). That output from the first level shifter 402 goes to a pair of inverters that are connected to the second non-zero intermediate voltage V.sub.MID2 (e.g., 0.6V) for the low supply and the first intermediate voltage V.sub.MID1 for the high supply. This limits the voltages going into the second level shifter 404 to be between V.sub.MID1 and V.sub.MID2. The second level shifter 404 then generates an output that operates from V.sub.MID2 (e.g., 0.6V) and V.sub.HI (e.g., 1.8V). Node ZCB is therefore at V.sub.HI while node ZTB is at V.sub.MID2 when the voltage power switch is not selected. Similarly, when the switch is selected, node ZCB will be at V.sub.MID2 and node ZTB will be at V.sub.HI.

(29) Accordingly, the output VGATEN of the voltage level shifter 122 shifts between two output voltages—second non-zero intermediate voltage V.sub.MID2 and the high voltage V.sub.HI. When the output is second non-zero intermediate voltage V.sub.MID2 the voltage power switch is enabled to pass the fuse programming voltage V.sub.HI to the downstream logic. On the other hand, when the output is high voltage V.sub.HI, the voltage power switch is enabled to pass a known safe voltage—the first non-zero intermediate voltage V.sub.MID1 to the downstream logic which is safe for all modes of operation.

(30) FIG. 5 shows a timing diagram of the various signals in accordance with implementations of the subject matter of this disclosure. Although FIG. 5 discusses specific voltage values, a person skilled in the art will understand that the specific voltage values are shown for illustrative purposes only and that any number of different voltage levels can be supplied based on IC specifications.

(31) As illustrated in FIG. 5, a high voltage V.sub.HI can be 1.8V in one embodiment and a low voltage V.sub.LO can be 0.75V. The voltages V.sub.HI and V.sub.LO are brought up during IC power up period. However, as discussed above in connection with FIGS. 1 and 3, because the voltage power switch is in a locked state, the voltages V.sub.HI and V.sub.LO, even when unknown, are not propagated through the IC. The reset signal RESETB generates a pulse as the unknown power supply is being brought up which forces a known locked state into the N latches of the lock circuit.

(32) The lock circuit waits for the unlock signal to unlock the voltage power switch. As illustrated in FIG. 5, the unlock signal is a clock signal pulsed N number of times. Although the embodiment of FIG. 5 shows four clock pulses corresponding to four latches, any number of latches can be included in the lock circuit. Once the valid unlock procedure is performed (i.e., an appropriate number of clock signals are pulsed through), the lock circuit output signal SYSRDYP is set to “HIGH” indicating that the voltage power switch is unlocked. Subsequently, when the voltage power switch is selected for fuse programming (i.e., when the SELECTH signal is “HIGH”), the output voltage VQPS of the voltage power switch outputs the high voltage V.sub.HI for fuse programming. As further illustrated in FIG. 5, the voltage power switch outputs a non-zero intermediate voltage V.sub.MID1 as VQPS at all other times (e.g., while the voltage power switch is in a locked state, or while the SELECTH signal is “LOW”) for safe operation of the device.

(33) Accordingly, the voltage power switch guarantees a known safe voltage V.sub.MID1 as VQPS while the initial voltages V.sub.HI and V.sub.LO are brought up during IC power up period are unknown by use of the lock circuit. Similarly, a “HIGH” SELECTH signal is also only selected when the voltage power switch is unlocked, thereby preventing the IC from receiving a high voltage during a non-fuse programming period. In this manner, the voltage power switch leverages the lock circuit to guarantee the passing of high voltages for fuse programming only during a specified duration. In one embodiment, the voltage power switch is configured to pass the high voltage during fuse programming for less than 0.2 seconds at a time and less than 10 seconds over the lifetime of a device. By employing the lock circuit and the voltage level shifter to control the voltages passed through to the components of the IC, the voltage power switch is able to increase the lifetime of the device.

(34) As used herein and in the claims which follow, the construction “one of A and B” shall mean “A or B.”

(35) It is noted that the foregoing is only illustrative of the principles of the invention, and that the invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.