Isolation circuit

An isolation circuit is provided. The isolation circuit is coupled to an output and an input node and includes a first set, a second switch set, and a body bias voltage generator. The first switch set couples a switch control node to a second voltage when a first voltage is at a first voltage level, and couples the switch control node to the input node when the first voltage is at a second voltage level. The second switch set couples the output node to the input node when the first voltage is at the first voltage level, and isolates the output node from the input node when the first voltage is at the second voltage level. The body bias voltage generator selectively provides a higher one of the first voltage and a voltage on the input node to a body of the second switch set.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 98123607, filed on Jul. 13, 2009. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.

TECHNICAL FIELD

The present invention relates to an isolation circuit.

BACKGROUND

FIG. 1is a schematic diagram of a conventional isolation circuit150. The isolation circuit150is coupled between a first circuit110and a second circuit190. The isolation circuit150includes a P-type transistor152and an N-type transistor154. The isolation circuit150can selectively couple or isolate the first circuit110and the second circuit190according to a signal S1and a signal S2.

However, the conventional isolation circuit150probably cannot assuredly couple (or assuredly isolate) the first circuit110and the second circuit190due to characteristics of the P-type transistor152and the N-type transistor154. For example, when the first circuit110and the second circuit190are required to be coupled, a signal transmitted between the first circuit110and the second circuit190can be probably truncated due to a body effect of the P-type transistor152and/or the N-type transistor154.

When the first circuit110and the second circuit190are required to be isolated, the P-type transistor152and/or the N-type transistor154probably form a leakage path for leaking the signal from the first circuit110to the second circuit190or from the second circuit190to the first circuit110.

SUMMARY

The present disclosure provides an isolation circuit. The isolation circuit is coupled between an output node of a first circuit and an input node of a second circuit. The first circuit is powered by a first voltage and a second voltage. The isolation circuit includes a first switch, a second switch, a third switch and a body bias voltage generator. A first terminal of the first switch is coupled to the input node of the second circuit, and a control terminal thereof is coupled to the first voltage. A first terminal of the second switch is coupled to a second terminal of the first switch, a second terminal thereof is coupled to the second voltage, and a control terminal thereof is coupled to the first voltage. A first terminal and a second terminal of the third switch are respectively coupled to the output node of the first circuit and the input node of the second circuit, and a control terminal thereof is coupled to the second terminal of the first switch. The body bias voltage generator is coupled to the first voltage and the input node of the second circuit, and selectively provides a higher one of the first voltage and a voltage on the input node of the second circuit to a body of the third switch.

The present disclosure provides an isolation circuit. The isolation circuit is coupled between an output node of a first circuit and an input node of a second circuit. The first circuit is powered by a first voltage and a second voltage. The isolation circuit includes a first switch set, a second switch set, and a body bias voltage generator. The first switch set is coupled to the first voltage and the input node of the second circuit, and is used for coupling a switch control node to the second voltage when the first voltage is at a first voltage level, and coupling the switch control node to the input node of the second circuit when the first voltage is at a second voltage level. The second switch set is coupled between the output node of the first circuit and the input node of the second circuit, wherein the second switch set is controlled by the switch control node to determine whether or not to isolate the output node of the first circuit from the input node of the second circuit. The body bias voltage generator is coupled to the first voltage and the input node of the second circuit, and selectively provides a higher one of the first voltage and a voltage on the input node of the second circuit to a body of the second switch set.

In order to make the aforementioned and other features and advantages of the present invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below.

DESCRIPTION OF THE EMBODIMENTS

Referring toFIG. 2,FIG. 2is a schematic diagram illustrating an isolation circuit according to an exemplary embodiment. The isolation circuit250is coupled between an output node211of a first circuit210and an input node291of a second circuit290. The first circuit210is powered by a first voltage Vin1and a second voltage. The second circuit290is powered by a third voltage Vin2and the second voltage. In the present embodiment, the first voltage Vin1and the third voltage Vin2can be a system voltage VDD, and the second voltage can be a ground voltage VSS. Functions of the isolation circuit250are: (1) when the first voltage Vin1is equal to the system voltage VDD required for normal operation of the first circuit210, so that the first circuit210is normally operated, the isolation circuit250couples the output node211of the first circuit210to the input node291of the second circuit290; (2) when the first voltage Vin1is cut off (for example, the first voltage Vin1is equal to the ground voltage VSS) to turn off the first circuit210, the isolation circuit250isolates the output node211of the first circuit210from the input node291of the second circuit290. Therefore, an input signal Y on the input node291cannot be leaked into the first circuit210through the output node211.

Therefore, the isolation circuit250includes a first switch set260, a second switch set270, and a body bias voltage generator280. The first switch set260is coupled to the first voltage Vin1and the input node291of the second circuit290. When the first voltage Vin1is at a first voltage level (for example, the first voltage Vin1is equal to the system voltage VDD), the first switch set260couples a switch control node266to the second voltage (for example, the ground voltage VSS). When the first voltage Vin1is at a second voltage level (for example, the first voltage Vin1is equal to the ground voltage VSS), the first switch set260couples the switch control node266to the input node291of the second circuit290.

The second switch set270is coupled between the output node211of the first circuit210and the input node291of the second circuit290, wherein the second switch set270is controlled by the first voltage Vin1and a voltage on the switch control node266, and determines whether or not to isolate the output node211of the first circuit210from the input node291of the second circuit290.

Therefore, when the first voltage Vin1is at the first voltage level (for example, the first voltage Vin1is equal to the system voltage VDD), the switch control node266is coupled to the second voltage and has the second voltage level (for example, the ground voltage VSS), so that second switch set270couples the output node211of the first circuit210to the input node291of the second circuit290. When the first voltage Vin1is at the second voltage level (for example, the first voltage Vin1is equal to the ground voltage VSS), the switch control node266is coupled to the input node291, so that the second switch set270isolates the output node211of the first circuit210from the input node291of the second circuit290.

The body bias voltage generator280is coupled to the first voltage Vin1and the input node291of the second circuit290. The body bias voltage generator280selectively provides a higher one of the first voltage Vin1and a voltage Y on the input node291to bodies of the first switch set260and the second switch set270.

To implement the aforementioned function of the first switch set260, the first switch set260of the present embodiment includes a first switch262and a second switch264. A first terminal (an upper end of the first switch262inFIG. 2) of the first switch262is coupled to the input node291of the second circuit290, and a control terminal (a right end of the first switch262inFIG. 2) of the first switch262is coupled to the first voltage Vin1. A first terminal (an upper end of the second switch264inFIG. 2) and a second terminal (a lower end of the second switch264inFIG. 2) of the second switch264are respectively coupled to a second terminal (a lower end of the first switch262inFIG. 2) of the first switch262and the second voltage VSS, and a control terminal (a right end of the second switch264inFIG. 2) of the second switch264is coupled to the first voltage Vin1.

In the present embodiment, the first switch262is a P-type transistor, and the second switch264is an N-type transistor. A body of the first switch262is coupled to a body bias voltage node271for receiving a body voltage provided by the body bias voltage generator280. A body of the second switch264is coupled to the ground voltage VSS.

To implement the aforementioned function of the second switch set270, the second switch set270of the present embodiment includes a third switch272and a fourth switch274. A first terminal (a left end of the third switch272inFIG. 2) and a second terminal (a right end of the third switch272inFIG. 2) of the third switch272are respectively coupled to the output node211of the first circuit210and the input node291of the second circuit290, and a control terminal (a lower end of the third switch272inFIG. 2) of the third switch272is coupled to the switch control node266. A first terminal (a left end of the fourth switch274inFIG. 2) and a second terminal (a right end of the fourth switch274inFIG. 2) of the fourth switch274are respectively coupled to the output node211of the first circuit210and the input node291of the second circuit290, and a control terminal (an upper end of the fourth switch274inFIG. 2) of the fourth switch274is coupled to the first voltage Vin1.

In the present embodiment, the third switch272is a P-type transistor, and the fourth switch274is an N-type transistor. A body of the third switch272is coupled to the body bias voltage node271for receiving the body voltage provided by the body bias voltage generator280. A body of the fourth switch274is coupled to the ground voltage VSS.

Generally, a body of a P-type transistor is required to be coupled to a positive bias. To ensure normal operations of the first switch262and the third switch272in case that the first voltage Vin1is at a low voltage level, the body bias voltage generator280provides the positive bias for the bodies of the first switch262and the third switch272.

FIG. 3AandFIG. 3Bare schematic diagrams illustrating two embodiments of the body bias voltage generator280ofFIG. 2. In the first embodiment ofFIG. 3A, the body bias voltage generator280includes a fifth switch282and a sixth switch284, wherein the fifth switch282and the sixth switch284are all P-type transistors. A first terminal (an upper end of the fifth switch282inFIG. 3A) of the fifth switch282is coupled to the first voltage Vin1. A second terminal (a lower end of the fifth switch282inFIG. 3A) of the fifth switch282is coupled to the bodies of the first switch262and the third switch272through the body bias voltage node271. A control terminal (a right end of the fifth switch282inFIG. 3A) of the fifth switch282is coupled to the input node291of the second circuit290. A first terminal (an upper end of the sixth switch284inFIG. 3A) and a second terminal (a lower end of the sixth switch284inFIG. 3A) of the sixth switch284are respectively coupled to the input node291of the second circuit290and the second terminal of the fifth switch282. A control terminal (a left end of the sixth switch284inFIG. 3A) of the sixth switch284is coupled to the first voltage Vin1. Bodies of the fifth switch282and the sixth switch284are all coupled to the second terminal of the fifth switch282. The body bias voltage generator280with such configuration can selectively provide a higher one of the first voltage Vin1and the voltage Y to the body bias voltage node271.

In the second embodiment ofFIG. 3B, the body bias voltage generator280includes a seventh switch286and an eighth switch288, wherein the seventh switch286and the eighth switch288are all N-type transistors. A first terminal (an upper end of the seventh switch286inFIG. 3B) of the seventh switch286is coupled to the first voltage Vin1. A second terminal (a lower end of the seventh switch286inFIG. 3B) of the seventh switch286is coupled to the bodies of the first switch262and the third switch272through the body bias voltage node271. A control terminal (a left end of the seventh switch286inFIG. 3B) of the seventh switch286is coupled to the first voltage Vin1. A first terminal (an upper end of the eighth switch288inFIG. 3B) and a second terminal (a lower end of the eighth switch288inFIG. 3B) of the eighth switch288are respectively coupled to the input node291of the second circuit290and the second terminal of the seventh switch286. A control terminal (a right end of the eighth switch288inFIG. 3B) of the eighth switch288is coupled to the input node291of the second circuit290. Bodies of the seventh switch286and the eighth switch288are all coupled to the ground voltage VSS. The body bias voltage generator280with such configuration can selectively provide a higher one of the first voltage Vin1and the voltage Y to the body bias voltage node271.

The isolation circuit250of the above embodiments can automatically couple or isolate the first circuit210and the second circuit290according to the first voltage Vin1. When the first voltage Vin1is equal to the system voltage VDD required for normal operation of the first circuit210, the first circuit210can transmits a signal to the second circuit290through the output node211, the isolation circuit250and the input node291. When the first voltage Vin1is cut off (for example, the first voltage Vin1is equal to the ground voltage VSS) to turn off the first circuit210, another circuit with a similar structure as that of the first circuit210can be used to provide the input signal Y to the second circuit290. Now, the isolation circuit250can ensure that the input signal Y provided by the other circuit is not leaked to the first circuit210through the output node211.

The isolation circuit of the present disclosure has various applications. For example, the isolation circuit of the present invention can be applied to a die repairing structure shown inFIG. 4.

InFIG. 4, a first die410and a second die430have a same design. The first die410includes a first circuit411, a first isolation circuit413, a second circuit415, a second isolation circuit417and a third circuit419. The first isolation circuit413is coupled between the first circuit411and the second circuit415, and the second isolation circuit417is coupled between the second circuit415and the third circuit419. Moreover, the first die410further includes bonding pads421-424and through silicon vias (TSV) TSV1and TSV2.

Similarly, the second die430includes a first circuit431, a first isolation circuit433, a second circuit435, a second isolation circuit437, and a third circuit439. The first isolation circuit433is coupled between the first circuit431and the second circuit435, and the second isolation circuit437is coupled between the second circuit435and the third circuit439. Moreover, the second die430further includes bonding pads425-428and the through silicon vias TSV3and TSV4.

If the first die410and the second die430can all be normally operated, coupling of the two dies through the die repairing structure ofFIG. 4is unnecessary, and the four isolation circuits413,417,433and437shown inFIG. 4are unnecessary to provide the isolation functions.

However, for example, the second circuit415of the first die410, and the first circuit431and the third circuit439of the second die430probably cannot be normally operated due to fabrication flaws or other reasons. Now, to avoid rejecting the first die410and the second die430to cause a waste, according to the die repairing structure ofFIG. 4, a conductive bump441can be used to couple the second circuit435of the second die430to the first isolation circuit413of the first die410, and a conductive bump442can be used to couple the third circuit419of the first die410to the second isolation circuit437of the second die430. Therefore, the first circuit411and the third circuit419of the first die410and the second circuit435of the second die430can be combined to form a patched circuit400that can be normally operated. Now, a signal transmission path is as that shown in dash lines ofFIG. 4.

Certainly, to normally operate the patched circuit400, the circuits415,431and439can be disabled by cutting off supplied powers thereof or though other approaches. Moreover, the second isolation circuit417of the first die410and the first isolation circuit433of the second die430are required to provide the isolation functions.

However, if the second isolation circuit417of the first die410and/or the first isolation circuit433of the second die430cannot substantially provide the isolation function, the patched circuit400probably cannot be normally operated. For example, if the first isolation circuit433of the second die430does not substantially isolate the first circuit431of the second die430, a signal transmitted from the first circuit411of the first die410to the second circuit435of the second die430can be leaked into the first circuit431of the second die, and such signal leakage may lead to a fact that the patched circuit400cannot be normally operated.

If the isolation circuits413,417,433and437ofFIG. 4are implemented by the aforementioned isolation circuit250, the isolation circuits413,417,433and437can substantially provide the coupling/isolation functions, and each of the isolation circuits413,417,433and437can avoid serving as a signal leakage path between two circuits when the two circuits are required to be isolated. Therefore, if the isolation circuits413,417,433and437ofFIG. 4are implemented by the aforementioned isolation circuit250, the patched circuit400can be normally operated.