# US 9,438,240 B1 · Biasing circuit for level shifter with isolation

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- Number: US 9,438,240 B1
- Document ID: US9438240B1
- Status: Granted
- Kind: B1
- Application number: 14/965,738
- Filed: 2015-12-10
- Granted: 2016-09-06
- Earliest claimed: 2015-08-31
- Assignees: Cypress Semiconductor Corporation
- Applicants: Cypress Semiconductor Corporation
- Inventors: Iulian C. Gradinariu; Jayant Ashokkumar; Bogdan Samson; Vijay Raghavan
- Web page: https://patentgrep.com/patent/US9438240B1

## CPC

- H03K 19/018507: {Interface arrangements}
- G11C 7/1057: {Data output buffers, e.g. comprising level conversion circuits, circuits for adapting load}
- G11C 7/1084: {Data input buffers, e.g. comprising level conversion circuits, circuits for adapting load}
- G11C 7/12: Bit line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, equalising circuits, for bit lines
- G11C 7/22: Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management
- G11C 16/06: Auxiliary circuits, e.g. for writing into memory
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- G11C: STATIC STORES (semiconductor memory devices H10B)

## Abstract

A circuit includes a biasing circuit that includes a load circuit coupled to a first node. The biasing circuit can output a biasing signal on the first node. The biasing circuit also includes a timer component and a current source. An input of the timer component is coupled to receive an isolation signal. The current source is configured to inject current for a period of time into the load circuit in response to a transition of the ISO signal between a high voltage and a low voltage. The biasing circuit also includes circuitry to generate an isolation delayed (ISO_DEL) signal. The ISO_DEL signal has a high voltage in response to the biasing signal being within a first threshold level and the ISO_DEL signal has a low voltage in response to the biasing signal being within a second threshold level. The biasing circuit outputs the ISO_DEL signal.

## Claims

### Claim 1

A circuit comprising:
a level shifter; and
a biasing circuit coupled to the level shifter, the biasing circuit comprising:
a load circuit coupled to a first node that is coupled to the level shifter, the biasing circuit to output a biasing signal on the first node;
a timer component and a current source, wherein an input of the timer component is coupled to receive an isolation (ISO) signal, wherein the current source is configured to inject current for a period of time, as determined by the timer component, into the load circuit in response to a transition of the ISO signal between a high voltage and a low voltage, wherein the high voltage is higher than the low voltage; and
circuitry to generate an isolation delayed (ISO_DEL) signal, wherein the ISO_DEL signal comprises a high voltage in response to the biasing signal being within a first threshold level and wherein the ISO_DEL signal comprises a low voltage in response to the biasing signal being within a second threshold level, the biasing circuit to output the ISO_DEL signal to the level shifter on a second node.

### Claim 2 (depends on 1)

The circuit of claim 1, wherein the biasing circuit further comprises a capacitor coupled between the first node and a ground potential, wherein the capacitor is charged in response to the current source injecting the current for the period of time into the load circuit.

### Claim 3 (depends on 1)

The circuit of claim 1, wherein the biasing circuit and the level shifter are comprised within a non-volatile memory device.

### Claim 4 (depends on 1)

The circuit of claim 1, wherein in response to the ISO signal comprising a high voltage, the ISO_DEL signal comprises a high voltage, wherein in response to the ISO signal comprising a low voltage when the biasing signal is within the first threshold level, the ISO_DEL signal comprises a high voltage and wherein in response to the ISO signal comprising a low voltage when the biasing signal transitions from the first threshold level to the second threshold level, the ISO_DEL signal comprises a low voltage.

### Claim 5 (depends on 1)

The circuit of claim 1, wherein the biasing circuit further comprises:
a first branch comprising a transistor, wherein the timer component is coupled to the transistor; and
a second branch that is configured to provide standby current to the load circuit in response to the current source ceasing injection of the current at an end of the period.

### Claim 6 (depends on 5)

The circuit of claim 5, wherein the transistor is activated in response to the transition of the ISO signal between the high voltage and the low voltage.

### Claim 7 (depends on 1)

The circuit of claim 1, wherein the circuitry to generate the ISO_DEL signal comprises at least one of: a pair of inverters or a voltage comparator.

### Claim 8 (depends on 1)

The circuit of claim 1, wherein the first threshold level comprises a voltage range between zero volts and a threshold level voltage and wherein the second threshold level comprises a voltage range between the threshold voltage level and a maximum voltage.

### Claim 9 (depends on 8)

The circuit of claim 8, wherein the biasing circuit further comprises a transistor, wherein the timer component is coupled to the transistor, wherein the timer component is configured to reset the timer component in response to the biasing signal approximately reaching the maximum voltage and after the biasing signal approximately reaches the maximum voltage, a second and third transistor control injection of a standby current to the load circuit which stabilizes the biasing signal until the biasing signal reaches a standby level voltage.

### Claim 10

A method for biasing a circuit, the method comprising:
receiving, at an input of a timer component, an isolation (ISO) signal;
in response to a transition of the ISO signal between a high voltage and a low voltage, injecting current for a period of time into a load circuit by a current source via control of the timer component, wherein the load circuit is coupled to a first node and wherein the high voltage is higher than the low voltage;
outputting on the first node a biasing signal;
generating an isolation delayed (ISO_DEL) signal, wherein the ISO_DEL signal comprises a high voltage in response to the biasing signal being within a first threshold level and wherein the ISO_DEL signal comprises a low voltage in response to the biasing signal being within a second threshold level; and
outputting on a second node the ISO_DEL signal.

### Claim 11 (depends on 10)

The method of claim 10, further comprising charging a capacitor in response to the injecting.

### Claim 12 (depends on 10)

The method of claim 10, further comprising:
ceasing the injecting of the current at an end of the period by deactivating a transistor coupled to the timer component; and
injecting standby current into the load circuit.

### Claim 13 (depends on 10)

The method of claim 10, wherein the biasing circuit is comprised within a non-volatile memory device.

### Claim 14 (depends on 10)

The method of claim 10, further comprising:
resetting the timer component in response to the biasing signal approximately reaching a maximum voltage; and
after the biasing signal approximately reaches the maximum voltage, injecting a standby current into the load circuit which stabilizes the biasing signal until the biasing signal reaches a standby level voltage.

### Claim 15

A biasing circuit comprising:
a load circuit comprising a plurality of transistors, the load circuit coupled to a first node;
a timer component, coupled to a first branch, wherein an input of the timer component is coupled to receive an isolation (ISO) signal;
a current source configured to inject current for a period of time, as determined by the timer component, into the load circuit, via the first branch, in response to a transition of the ISO signal between a high voltage and a low voltage, wherein the high voltage is higher than the low voltage; and
circuitry to generate an isolation delayed (ISO_DEL) signal,
wherein the ISO_DEL signal comprises a high voltage in response to a biasing signal carried on the first node being within a first threshold level,
wherein the ISO_DEL signal comprises a low voltage in response to the biasing signal being within a second threshold level, and
wherein the biasing circuit outputs the biasing signal on the first node and outputs the ISO_DEL signal on a second node.

### Claim 16 (depends on 15)

The biasing circuit of claim 15, further comprising a capacitor that is charged in response to the current source injecting the current for the period of time into the load circuit.

### Claim 17 (depends on 15)

The biasing circuit of claim 15, further comprising a second branch, wherein in response to the period of time ending, the current source ceases injection of the current and the second branch is configured to provide standby current to the load circuit.

### Claim 18 (depends on 15)

The biasing circuit of claim 15, wherein the biasing circuit outputs an output signal configured to be provided to a non-volatile memory device.

### Claim 19 (depends on 15)

The biasing circuit of claim 15, wherein the first threshold level comprises a voltage range between zero volts and a threshold level voltage and wherein the second threshold level comprises a voltage range between the threshold level voltage and a maximum voltage.

### Claim 20 (depends on 15)

The biasing circuit of claim 15, wherein the biasing circuit outputs the biasing signal and the ISO_DEL signal to a level shifter, wherein the level shifter transforms a received low voltage signal to a high voltage signal.