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Automatic threshold voltage control circuit and signal converting circuit and method thereof
| Details |
Inventors: Wang, Yao-Chi;
Assignee: Sunplus Technology Co., Ltd. (Hsinchu, TW)
Primary Examiner: Nguyen; Linh
Assistant Examiner:
Attorney, Agent or Firm: Jianq Chyun IP Office
An automatic threshold voltage control circuit is provided. The circuit comprises a first capacitor, a clock generator, and a switching capacitor network. Wherein the switching capacitor network, receives an analog signal and a plurality of clock signals from the clock generator, where the switching capacitor network stores a portion of charges of the analog signal according to one clock signal, and outputting the portion of charges in according to another clock signal. The portion of charges being associated with the first capacitor generates a threshold voltage. A plurality of sensor control switches is adopted in the present invention in replace of the resistor in the conventional RC filter. Hence, it can be easily integrated into one chip and number of the external devices is reduced, so that hardware costs down. In addition, RC constant can be adjusted by tuning the frequency of the clock signal. |
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DETAILED DESCRIPTION As mentioned above, the conventionally RC filer circuit is implemented for automatic threshold voltage control, however, the resistor and capacitor occupies a significant chip area of IC, integration is not considered in this case.
External resistor and capacitor can be connected to the IC to obtain the same effect, yet device cost is increased.
Hence, the present invention provides an automatic threshold voltage control circuit to eliminate the drawbacks of the conventional RC filter circuit.
FIG.
3 illustrates an automatic threshold voltage control circuit and the analog-to-digital converter circuit thereof in accordance with one preferred embodiment in the present invention.
The circuit of this preferred embodiment comprises a capacitor C1, a capacitor C2, a sensor switcher S1, a sensor switcher S2, and a clock generator 320.
The switching capacitor network 330 receives the clock signals from the clock generator to control one of the sensor switchers S1 and S2 so that only one of S1 and S2 is off and the other is on.
When the sensor switchers S1 and S2 are on and off alternatively in response to the clock signals, the capacitor C1 will store a portion of charges .
DELTA.
Q of the analog signal V.
sub.
IN when the sensor switcher S1 is on, wherein .
DELTA.
Q=C1(V.
sub.
IN-V.
sub.
REF) (1) In this preferred embodiment, the capacitance of C1 is 0.
5 pF, for example.
The average current I.
sub.
avg flowing through the switching capacitor network 330 is shown as follows: I.
sub.
avg=.
DELTA.
Q/T=C1*f(V.
sub.
IN-V.
sub.
REF) (2) In this embodiment, the frequency f is 40 KHz, for example.
The equivalent resistor R.
sub.
eff of the switching capacitor network 330 is R.
sub.
eff=(V.
sub.
IN-V.
sub.
REF)/I.
sub.
avg=1(C1*f) (3) If the clock generator 320 is appropriately adjusted so that the clock signal controlling the sensor control switch S1 and the clock signal controlling the sensor control switch S2 possess the same frequency with different phases yet not overlapping, the switching capacitor network 330 associated with the capacitor C2 serves as RC filter and manages to generate the threshold voltage V
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Coded 
