Synchronous sense amplifier with temperature and voltage compensated translator

• US 6,037,807 A
• Filed: 05/18/1998
• Issued: 03/14/2000
• Est. Priority Date: 05/18/1998
• Status: Expired due to Term

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Inventors: Fang, Wen-Kuan, Tien, Ta-Ke, Wu, Chau-Chin
• Primary Examiner(s): TRAN, TOAN V
• Application Number:
  US09/080,710
• Time in Patent Office: 666 Days
• Field of Search: 327/51-57, 327/63, 327/65, 327/66, 327/67, 327/77, 327/83, 327/89, 327/362, 327/513, 327/560-563
• US Class Current: 327/52
• CPC Class Codes: G11C 7/06 Sense amplifiers; Associated circuits , e.g. timing or triggering circuits

Abstract

A bias control circuit for controlling the bias current in a sense amplifier circuit. The bias control circuit maintains a substantially constant bias current when the V_CC supply voltage decreases, thereby maintaining the operating speed of the sense amplifier circuit at a predetermined level. The bias control circuit also increases the bias current as the temperature of the sense amplifier circuit increases, thereby maintaining the operating speed of the sense amplifier circuit at the predetermined level. Furthermore, the bias circuit controls the logic low voltage provided by the sense amplifier circuit to be less than a predetermined threshold value, even as the V_CC supply voltage increases.

Claims

1. A circuit comprising:

a sense amplifier circuit which operates in response to a V_CC supply voltage, the sense amplifier circuit having an associated bias current; and

a bias circuit coupled to the sense amplifier circuit, the bias circuit controlling the bias current to maintain an operating speed of the sense amplifier circuit when the V_CC supply voltage decreases, and when the temperature of the circuit increases, wherein the bias circuit comprises circuitry for controlling a logic low voltage provided by the sense amplifier circuit to be less than a predetermined threshold value.

2. The circuit of claim 1, wherein the circuitry for controlling the logic low voltage comprises a transistor having a threshold voltage, wherein the transistor clamps the logic low voltage provided by the sense amplifier circuit to the threshold voltage.

8. The circuit of claim 1, wherein the sense amplifier circuit comprises:

a cross-coupled amplifier having a pair of output terminals;

a first differential amplifier having a pair of input terminals coupled to the output terminals of the cross-coupled amplifier in a first order; and

a second differential amplifier having a pair of input terminals coupled to the output terminals of the cross-coupled amplifier in a second order which is reversed from the first order.

3. A circuit comprising:

a sense amplifier circuit which operates in response to a V_CC supply voltage, the sense amplifier circuit having an associated bias current; and

a bias circuit coupled to the sense amplifier circuit, the bias circuit controlling the bias current to maintain an operating speed of the sense amplifier circuit when the V_CC supply voltage decreases, and when the temperature of the circuit increases, wherein the bias circuit comprises;

a differential amplifier having a first input terminal coupled to receive a first control voltage having a positive slope with respect to temperature;

a voltage divider circuit coupled to provide a reference voltage to a second input terminal of the differential amplifier;

a feedback circuit coupled to an output terminal of the differential amplifier and the second input terminal of the differential amplifier, wherein the feedback circuit controls the reference voltage to be approximately equal to the first control voltage by varying a control current through the feedback circuit; and

a translation circuit for translating variations in the control current into variations in the bias current.

4. The circuit of claim 3, wherein the feedback circuit comprises a transistor having a source coupled to receive the V_CC supply voltage, a drain coupled to the second input terminal and a gate coupled to the output terminal of the differential amplifier.

5. The circuit of claim 3, wherein the voltage divider circuit comprises:

a first resistor having a first terminal coupled to receive the VCC supply voltage and a second terminal coupled to the second input terminal of the differential amplifier; and

a second resistor having a first terminal coupled to the second input terminal of the differential amplifier and a second terminal coupled to a ground supply terminal.

6. The circuit of claim 3, wherein the translation circuit comprises at least one current mirror circuit.

7. The circuit of claim 3, further comprising a voltage compensation circuit coupled to the first input terminal of the differential amplifier, wherein the voltage compensation circuit is configured to provide a control voltage having a positive slope with respect to temperature.

9. A method of operating a sense amplifier circuit, the method comprising the steps of:

operating the sense amplifier circuit in response to a V_CC supply voltage;

biasing the sense amplifier circuit with an associated bias current;

maintaining the bias current at a predetermined level as the V_CC supply voltage decreases, thereby maintaining a predetermined operating speed within the sense amplifier circuit;

increasing the bias current when the temperature of the sense amplifier circuit increases, thereby maintaining the predetermined operating speed within the sense amplifier circuit; and

limiting a logic low output signal provided by the sense amplifier circuit to be lower than a predetermined threshold voltage, even as the V_CC supply voltage increases.

10. A method of operating a sense amplifier circuit, the method comprising the steps of:

operating the sense amplifier circuit in response to a V_CC supply voltage;

biasing the sense amplifier circuit with an associated bias current;

maintaining the bias current at a predetermined level as the V_CC supply voltage decreases, thereby maintaining a predetermined operating speed within the sense amplifier circuit; and

increasing the bias current when the temperature of the sense amplifier circuit increases, thereby maintaining the predetermined operating speed within the sense amplifier circuit, wherein the step of increasing the bias current further comprises the steps of;

applying a first voltage to a first input terminal of a differential amplifier, wherein the first voltage has a positive slope with respect to temperature;

applying a reference voltage to a second input terminal of the differential amplifier;

generating an output voltage with the differential amplifier, the output voltage being inversely related to the first voltage;

providing a feedback current to the second input terminal of the differential amplifier in response to the output voltage, wherein the feedback current is inversely related to the output voltage; and

translating the feedback current to the sense amplifier circuit to generate the bias current.