Charge pump circuit operating responsive to a mode

1. Priority Info This application claims priority from Korean Patent Application Number 2003-46799, filed Jul. 10, 2003, that we incorporate here by reference.

2. Field of the Invention

The present invention relates to high-voltage generators and, more specifically, to charge pump circuits operating responsive to a mode that enables selection of a power voltage or an external high voltage.

3. Discussion of the Related Art

FIG. 1 is a block diagram of a conventional charge pump circuit. As shown in FIG. 1 , the conventional charge pump circuit comprises a voltage level sensing block 20 , an oscillator 30 , and a charge pump block 10 . The voltage level sensing block 20 senses a level of the output voltage Vout. The oscillator 30 generates pulse signals PUL, /PUL responsive to a signal DET output from the block 20 . The charge pump block 10 performs a pumping operation.

The voltage level sensing block 20 , as shown in FIG. 2 , comprises a differential amplifier. The voltage level sensing block 20 operates responsive to a pumping enable signal enPUMP and compares output voltage Vout with reference voltage VREF. The voltage level sensing block 20 generates a level sensing signal DET.

As shown in FIG. 3 , the oscillator 30 comprises one NOR gate G 1 and four invertors INV 1 , INV 2 , INV 3 and INV 4 . And the oscillator 30 responds to the level sensing signal DET to generate the complimentary pulse signals PUL, /PUL.

The charge pump block 10 comprises a charge supply part 11 and a plurality of charge pump parts 12 - 15 . The charge supply part 11 receives an external voltage VCC and provides supply charges to a first charge pump part PSI. The charge pump parts PS 1 , PS 2 , PS 3 , . . . , PSn are serially connected. The charge pump parts 12 - 15 generate an output voltage Vout by pumping charges supplied from the charge supply part 11 . An odd number of pump parts 11 - 15 operates responsive to the pulse signal PUL, while an even number of them operate responsive to the inverted pulse signal/PUL.

The conventional charge pump shown in FIG. 1 operates as follows.

When the pumping enable signal enPUMP is in a predetermined logic level, e.g., becomes high, the voltage level sensing block 20 senses the level of the output voltage Vout by comparing output voltage Vout to a reference voltage VREF. If the reference voltage VREF is larger than the output voltage Vout, the voltage level sensing block 20 generates the level sensing signal DET having a predetermined state, e.g., high. On the other hand, if the output voltage Vout is larger than reference voltage VREF, the voltage level sensing block 20 generates the level sensing signal DET having e.g., a low state. The oscillator 30 provides the pulse signals PUL and/PUL to the charge pump parts PS 1 , PS 2 , PS 3 , . . . , PSn responsive to the level sensing signal DET. That is, if the level sensing signal (DET) is enabled, all charge pump parts PS 1 , PS 2 , PS 3 , . . . , PSn increase the level of the output voltage Vout. If the level sensing signal (DET) is disable, all charge pump parts PS 1 , PS 2 , PS 3 , . . . , PSn decrease the level of the output voltage Vout.

The conventional charge pump circuit pre-charges the output voltage Vout corresponding to the external voltage VCC at each node of the charge supply part 11 and the charge pump parts 12 - 15 . Accordingly, the time to precharge increases in the output voltage Vout. This additional time is undesired, particularly where testing integrated chips that require high voltages quickly. A need remains for an improved charge pump circuit.

A feature of the invention is to address disadvantages associated with prior charge pumps.

Another feature of the invention is to provide a charge pump that operates both in a test and in a general operation mode.

A charge pump circuit includes at least one charge pump part. A voltage level sensing block generates a level sensing signal by sensing an output voltage. An oscillator 30 generates complementary pulse signals responsive to the level sensing signal. And a selecting circuit block generates a selected voltage that is one of a high voltage and a supply voltage to the at least one charge pump part, the high voltage having a level higher than the supply voltage.

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a block diagram of a conventional charge pump circuit.

FIG. 2 is a circuit diagram of the sensing level sensing block 20 shown in FIG. 1 .

FIG. 3 is a circuit diagram of the oscillator 30 shown in FIG. 1 .

FIG. 4 is a block diagram of an embodiment of a charge pump circuit according to the present invention.

FIG. 5 is a circuit diagram of an embodiment of a charge pump part shown in FIG. 4 .

FIG. 6 is a circuit diagram of an embodiment of the selector shown in FIG. 4 .

FIG. 7 is a circuit diagram of an embodiment of the detector shown in FIG. 4 .

FIG. 8 is a graph of the output voltage for the charge pump circuit of the present invention.

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The present invention is, however, not limited to the embodiments illustrated here. Rather, the embodiments are introduced to provide easy and complete understanding of the scope and spirit of the present invention.

FIG. 4 is a block diagram of an embodiment of the charge pump circuit according to the present invention. Referring to FIG. 4 , the charge pump circuit comprises a charge pump block 100 , a selecting circuit block 200 , an oscillator 300 , and a voltage level sensing block 400 .

The pump block 100 comprises a charge supply part 110 , a plurality of charge pump parts 120 , 130 , 140 , and 150 and a charge trapping part 160 , all serially connected.

The charge supply part 110 provides a charge corresponding to voltage Vsel provided, in turn, by the selecting circuit block 200 to a first charge pump part 120 . The charge pump parts 120 , 130 , 140 and 150 pre-charge a charge corresponding to the selected voltage Vsel and pumps a charge to a next serially connected charge supply part. The charge trapping part 160 traps the pumped charge through each charge pump part 120 , 130 , 140 and 150 to generate an output voltage Vout. FIG. 5 is a block diagram of the charge pump block 100 shown in FIG. 4 .

Referring to FIG. 5 , the sensing level part 400 senses level of output voltage Vout when a pumping enable signal enPUMP is enabled. In other words, if the output voltage Vout is smaller than the reference voltage Vref, the level sensing signal DET is enabled. If the output voltage Vout is larger than the reference voltage Vref, on the other hand, the level sensing signal DET is disabled.

The oscillator 300 generates complementary pulse signals PUL and /PUL responsive to the level sensing signal DET. If the level sensing signal DET is enabled, all charge pump parts 120 , 130 , 140 and 150 increase the output voltage Vout. If the level sensing signal DET is disabled, the charge pump parts 120 , 130 , 140 and 150 do not operate.

Referring to FIG. 4 , the charge pump circuit according to the present invention comprises a selecting circuit block 200 . The selecting circuit block 200 includes a selector 210 and a detector 220 . In the specification power supply voltage VCC refers to the power voltage operating in general operation mode. The voltage VPP refers to a high voltage provided externally during a test operation mode. The high voltage VPP may be applied externally in the test operation mode as well as during the general operation mode.

The selecting circuit block 200 comprises the selector 210 and the detector 220 . The selector 210 selects between the power voltage VCC and the high voltage VPP. The detector 220 detects the level of the high voltage VPP to generate detection signal VDET. The detector 220 enables the detection signal VDET when the high voltage VPP is higher than the power voltage VCC. The selector 210 switches between the power voltage VCC to the high voltage VPP responsive to the detection signal VDET. Put differently, the signal VSEL is VCC in the general operation mode and VPP in the test operation mode allowing for a high voltage within a short time. The selector 210 and the detector 220 are more fully described referring to FIGS. 6 and 7 .

FIG. 5 is a circuit diagram of the charge pump block 100 shown in FIG. 4 . Referring to FIG. 5 , the charge pump block 100 operates as follows. The charge pump block 100 comprises the charge supply part 110 , charge pump parts 120 , 130 , 140 and 150 , and the charge trapping part 160 .

The charge supply part 110 comprises high-voltage PMOS transistor P 110 available simultaneously in general and test operation modes. The high-voltage PMOS transistor P 110 is connected between node 1 and node 2 . Source and bulk terminals of the high-voltage PMOS transistor P 110 are connected to the node 1 . A drain terminal is connected to the node 2 . A gate is connected to a ground GND terminal. The charge supply part 110 is available for a charge supply device and supplies charges to a first charge pump part 120 located in next part. For example, if VSEL is VCC in the general operation mode, charges corresponding to the power voltage VCC are pre-charged at node 2 . In addition, if VSEL is VPP in test operation mode, charges corresponding to the high voltage VPP are pre-charged at node 2 .

Each charge pump part 120 , 130 , 140 and 150 comprises one PMOS transistor, e.g., transistor P 120 , one capacitor, e.g., capacitor C 120 , and one high-voltage NMOS transistor, e.g., transistor N 120 . The high-voltage NMOS transistor, e.g., transistor N 120 , operates both in the general operation mode as well as the test operation mode. An odd number (or even number) of the charge pump parts operates responsive to the pulse signal PUL, while an even number (or odd number) of the charge parts operates responsive to the inverted pulse signal/PUL.

In the specification, pump parts except for the first charge pump part 120 is omitted for clarity. We describe only charge part 120 for simplicity. A person of reasonable skill should realize that other charge parts operate and include similar elements.

A source terminal of the PMOS transistor P 120 is connected to the node 2 . The source terminal of the PMOS transistor P 120 is used as a charge transfer device. A drain terminal and a gate terminal are connected to the node 3 . A bulk terminal is in a floating state. A capacitor C 120 is used as a charge pumping device and is connected between the node 3 and the node 8 . The pulse signal PUL or/PUL is applied to the capacitor C 120 . The drain of the NMOS transistor N 120 is connected to the node 1 . A source terminal is connected to the node 3 , and the bulk terminal is connected to ground GND. The gate and drain terminals of high-voltage NMOS transistor N 120 are used as a pre-charge device. The high-voltage NMOS transistor N 120 pre-charges charges corresponding to the selecting voltage VSEL at the node 3 . For example, if the threshold voltage of the high-voltage NMOS transistor N 120 is VTH, charges corresponding to VSEL-VTH are pre-charged. In other words, charges corresponding to VCC-VTH are pre-charged in the general operation mode, and charges corresponding to VPP-VTH are pre-charged in the test mode.

The charge trapping part 160 comprises one PMOS transistor P 160 and one capacitor. The PMOS transistor P 160 is used as charge transfer device, and the capacitor is used as charge trapping device. The charge trapping part 160 generates the output voltage Vout.

FIG. 6 is a circuit diagram of the selector 210 shown in FIG. 4 . Referring to FIG. 6 , the selector 210 uses a level shifter to control the high voltage VPP. The selector 210 comprises high-voltage NMOS transistors N 211 to N 218 , high-voltage PMOS transistors P 211 to P 218 and P 210 _I where i=1 to 4, and two serially connected inverters. The level shifter selects between the power voltage VCC and the high voltage VPP. For instance, the high-voltage NMOS transistors N 216 and N 217 turn on in the test operation mode where the detection signal VDET is enabled. The high-voltage PMOS transistors P 210 _ 3 and P 210 _ 4 turn on. As a result, VSEL is equal to VPP. However, since the high-voltage NMOS transistors N 212 and N 213 are turned off, the high-voltage PMOS transistors P 210 _ 1 and P 210 _ 2 are also turned off. Accordingly, VSEL is not equal to VCC. To the contrary, VSEL is equal to VCC in general operation mode where the detection signal VDET is disabled.

FIG. 7 is a circuit diagram of the detector 220 shown in FIG. 4 . Referring to FIG. 7 , the detector 220 comprises high-voltage PMOS transistors P 221 and P 222 , high-voltage NMOS transistors N 221 -N 224 , a high-voltage inverter HV INV and a low-voltage inverter LV INV. The detector 220 can be used in the general as well as test operation mode requiring high voltage. For example, if external high-voltage VPP is lower than the power voltage VCC, a node A has a voltage that is VCC-VTH. Accordingly, the PMOS transistor P 221 is off. At this time, node B voltage is ground GND. In another approach, if external high-voltage VPP is higher than the power voltage VCC, node A voltage is VPP-VTH. As VPP increases, node B has high enough voltage to inverse the output of the high-voltage inverter HV INV. This output generates a high detection signal VDET through passing the low-voltage inverter LV INV.

FIG. 8 is a graph of the output voltage Vout depending on whether the charge pump circuit uses the power voltage VCC or external high voltage VPP. Settling time is a time required for the pumping operation to obtain a wanted output voltage Vout. Referring to FIG. 8 , if the selected voltage VSEL is under the condition that the power voltage VCC is equal to 1.8V, and the external voltage VPP is equal to 8 V, it is known that four times settling times (STp) is required to obtain an output voltage Vout of 10V. That is, when external high voltage VPP is supplied with the power voltage VCC, a wanted output voltage Vout can be obtained within a shorter time.

As previously mentioned, the charge pump circuit can obtain a wanted output voltage Vout within a short time by further including selective means capable of applying high voltage rather than the power voltage VCC.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.