Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Integrated structure
Reexamination Certificate
1999-01-29
2001-05-08
Kim, Jung Ho (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Integrated structure
C327S536000
Reexamination Certificate
active
06229385
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to implementing control features on an integrated circuit (IC). In particular, this invention relates to implementing a control feature on an IC without adding a dedicated pin to implement that feature.
The invention is described below as it applies to a charge pump circuit; however, persons skilled in the art will appreciate that the principles of the present invention can be applied to other integrated circuits as well. By enabling additional control features to be added to an IC without adding extra pins, the invention preserves valuable space on the circuit board.
Direct current to direct current (DC—DC) conversion circuits can be implemented using an inductor based topology or a capacitor based topology (e.g., a charge pump). Each type of converter topology has its own advantages and disadvantages. The inductor based topology requires fewer power switches and can be implemented in fewer pins than the capacitor based topology. For example, a conversion circuit that boosts voltage four times (a quadruplet) can be implemented with an inductor based topology using three pins, while a capacitor based topology requires a minimum of eight pins.
The inductor based topology, however, also has several disadvantages. These circuits are more complex to design than capacitor based topologies because they require numerous external components in addition to many internal IC controls. Moreover, they require magnetic energy storage, which often is difficult to stabilize and radiates EMI waves.
Capacitor based topology requires a minimum of eight power switches and eight pins to operate. Adding a control feature will normally increase the pin count to at least nine pins. To avoid increasing pin count and consuming additional space on the circuit board, the present invention enables the designer to add a control feature to the IC without requiring additional pins be added to the IC.
SUMMARY OF THE INVENTION
Accordingly, one of the objects of the invention is to enable additional control features to be added to an IC without adding additional dedicated pins.
The present invention provides an additional control feature to the IC by assigning multiple duties to one of the pins. In a preferred embodiment, a shutdown control feature is added to a quadrupler charge pump IC. Persons skilled in the art, however, will appreciate that the present invention can be utilized in various circuits, such as, for example, a doubler, a sextupler, an octupler, etc. charge pump IC or in any other IC where it is desirable to preserve a low pin count.
In accordance with the invention, a charge pump circuit that normally has two terminal pins attached thereto is provided with an operating and a sampling state. A timing circuit is used to provide a recurring signal, such as once every sixteen clock cycles, that places the charge pump into the sampling state for the duration of the recurring signal (normally one clock pulse). A sampler circuit then samples one of the doubler circuit's pins while the doubler circuit is in the sampling state. The control feature (e.g., shutdown) is implemented based on the sampled signal. For instance, the internal circuit clock can be disabled when there is an external pull-down signal on the sampled pin so that the IC is effectively shut down. The control feature also could be implemented with a external pull-up signal or any number of known control signals. Thus, a shutdown control feature is added to a charge pump IC without adding an additional dedicated pin. The sampled signal could be used to implement any number of different control features, such as modifying the regulator voltage, modifying the internal clock frequency or enabling an auxiliary function of the IC.
REFERENCES:
patent: 5672988 (1997-09-01), Nelson et al.
patent: 5812017 (1998-09-01), Golla et al.
patent: 5943271 (1999-08-01), Fujita
patent: 5959854 (1999-09-01), Okada
patent: 6041011 (2000-03-01), Umezawa et al.
“500kHz and 1MHz High Efficiency 1.5A Switching Regulators,”Linear Technology Corporation Data Sheet, LT1372/1377.
Bell David B.
Nork Samuel H.
Fish & Neave
Kim Jung Ho
Linear Technology Corporation
Morris Robert W.
Straub Stephen T.
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