CN100345383C - Analog front end apparatus with adjustable bandwidth wave filtering function - Google Patents
Analog front end apparatus with adjustable bandwidth wave filtering function Download PDFInfo
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- CN100345383C CN100345383C CNB031362532A CN03136253A CN100345383C CN 100345383 C CN100345383 C CN 100345383C CN B031362532 A CNB031362532 A CN B031362532A CN 03136253 A CN03136253 A CN 03136253A CN 100345383 C CN100345383 C CN 100345383C
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Abstract
The present invention relates to an analog front end device with an adjustable bandwidth wave filtering function, which comprises an input buffer and an analogue/digital converter, wherein the adjustable bandwidth wave filtering function can be integrated into the analogue/digital converter or the input buffer. When integrated into the analogue/digital converter, the adjustable bandwidth wave filtering function can be realized by a capacitor and a switch arranged in the analogue/digital converter, wherein the capacitor is originally used for sampling and keeping analogue signals. A switch module comprises a plurality of transistor switches which are connected in parallel each other, one or a plurality of parallel connection are selected from the transistor switches by option codes and are used as equivalent resistors so as to be connected in series with capacitors, and a wave filtering circuit is formed, wherein the option codes multiple-or codes or thermometer codes.
Description
Technical field
The present invention is relevant for a kind of analog front-end device of tool filter function, and particularly relevant a kind of analog front-end device with BREATHABLE BANDWIDTH filter function.
Background technology
For a long time, and cathode ray tube (Cathode Ray Tube, CRT) Display Technique is the main flow of display always, goes through the refining of quenching of many decades, its development of technologies is very ripe.In recent years, because digitized trend of the times, Display Technique has also had sizable change, and LCD (LCDmonitor) is a dark horse, and the situation that replaces CRT monitor is arranged greatly.
In personal computer etc. was used, because many display cards (VGA card) all can only be exported analog picture signal, so LCD could be shown after the analog signal conversion that receives of handle be digital signal earlier.For this reason, just need in the LCD controller of display (LCD controller) AFE (analog front end) (analog front end, AFE) device and ratio processor (scalar), carry out works of treatment such as conversion of signals and convergent-divergent computing; Wherein, analog front-end device is in order to analog picture signal is converted to data image signal, and the ratio processor is then according to data image signal computing in addition, to present the image of different resolution.Along with the evolution of manufacturing technology and the lifting of assembly integrated level, present trend is that analog front-end device, ratio processor and some peripheral circuits are integrated in the same chip (chip), is called the LCD control chip.
Typical analog front-end device as shown in Figure 1, form by the identical circuit of three covers, respectively in order to redness (R) analog signal RA, green (G) analog signal GA and blueness (B) analog signal BA are converted to red digital signal RD, green digital signals GD and blue digital signal BD.Further, every suit circuit is again by clamper (clamper) 110, input buffer (input buffer) IB and analog/digital converter (analog to digital converter, ADC) 130 compositions, analog picture signal can utilize clamper 110 to remain on the level (level) of setting earlier, again with input buffer IB with signal damping after feed-in analog/digital converter 130 change.In addition, analog front-end device also comprises clock pulse generator (clock generator) 150 and bandgap voltage reference circuit (bandgapvoltage reference) 170 etc., the clock pulse signal CLK that clock pulse generator 150 can provide analog/digital converter 130 to need, the conditioning signal ADJ that bandgap voltage reference circuit 170 is produced then is used for regulating gain (gain) and the offset voltage (offset voltage) of input buffer IB.
Input buffer IB can utilize source follower (source follower) to be achieved, as shown in Figure 2.Input buffer IB is made of impedance Rs, current source Io and transistor Mp, RGB analog signal from clamper 110 feed-ins can be passed through the input voltage vin equivalence, before feed-in transistor Mp, can be by the feed-in opportunity of transistor switch control analog signal, can be during this transistor switch conducting by in addition equivalence of impedance Rs.Can utilize capacitor C to carry out the sampling and maintenance (the samle and hold) work of signal during RGB analog signal feed-in analog/digital converter 130 earlier, when switch SW 1, analog signal can be taken a sample by capacitor C during SW2 conducting (turn on), after the sampling with switch SW 1, SW2 turn-offs (turn off) can make signal maintain, with the signal source as late-class circuit; Wherein switch SW 1, and SW2 for example is a transistor switch.
In actual applications, because printed circuit board (PCB) (printed circuit board, PCB) configuration (Layout) or other environmental factor often cause being attended by high-frequency noise in the RGB analog signal, occur ripples line or other distortion phenomenon on the lcd screen and make.The means of head it off are design one filter circuits on circuit.Actually, the bandwidth of filter circuit designs approximately more than 3 frequencys multiplication of clock pulse signal CLK, and also even the frequency of clock pulse signal CLK is 140MHz, and then the bandwidth of filter circuit is about 500MHz.Because the LCD control chip must be contained the display mode of lowest frequency to high frequency when using, so the filter circuit in the chip also must have adjustable bandwidth (for example bandwidth can be 75,150,300, optionally regulate between 500MHz), just possess practical value.But reality is, in chip, realize this on a large scale bandwidth and to the requirement of the linearity than the back grade also high active filter circuit of ADC, be very very difficult.
Summary of the invention
In view of this, purpose of the present invention is exactly in that a kind of analog front-end device with BREATHABLE BANDWIDTH filter function is provided, with the high-frequency noise under the filtering plurality of display modes.
According to purpose of the present invention, a kind of analog front-end device with BREATHABLE BANDWIDTH filter function is proposed, being summarized as follows of this device:
Analog front-end device comprises input buffer and analog/digital converter, and the filter function of BREATHABLE BANDWIDTH can be integrated in analog/digital converter or the input buffer.When being integrated in analog/digital converter, can realize by the electric capacity of analog/digital converter inside and switch module, wherein the usefulness of former sampling and the maintenance as analog signal of this electric capacity.Switch module comprises a plurality of transistor switches that are connected in parallel to each other, and can form filter circuit according to option code by selecting one (or a plurality of parallel connection) in the transistor switch with as equivalent resistance and this capacitances in series.Wherein option code can be one yard of multiselect or thermometer-code.When being integrated in input buffer, can utilize a plurality of transistors that are connected in parallel to each other to form transistor modular, be filter circuit according to option code by selecting one or more parallel connection in the transistor; Or utilize a plurality of current sources that are connected in parallel to each other to form current source module, by selecting one or more parallel connection in the current source, reach the purpose of regulating filtering bandwidth according to option code to regulate the output total current.
Description of drawings
For above-mentioned purpose of the present invention, feature and advantage can be become apparent, a preferred embodiment cited below particularly, and conjunction with figs. are described in detail as follows:
Fig. 1 represents typical analog front-end device.
Fig. 2 represents to realize with source follower the scheme of input buffer.
Fig. 3 represents the analog/digital converter that proposed according to embodiments of the invention one.
Fig. 4 represents transistorized small-signal equivalent circuit in the input buffer.
Fig. 5 represents a kind of input buffer of being proposed according to embodiments of the invention two.
Fig. 6 represents the another kind of input buffer that proposed according to embodiments of the invention two.
The drawing reference numeral explanation
110: clamper
130: analog/digital converter
150: clock pulse generator
170: bandgap voltage reference circuit
310: switch module
330: analog/digital converter
510: transistor modular
610: current source module
IB: input buffer
RA: red analog signal
GA: green analog signal
BA: blue analog signals
RD: red digital signal
GD: green digital signals
BD: blue digital signal
CLK: clock pulse signal
ADJ: conditioning signal
C: electric capacity
Rs: impedance
SW1, SW2, SW3, SW4, SW5: transistor switch
Mp, Mp1, Mp2, Mp3, Mp4: transistor
Io, I1, I2, I3, I4: current source
Embodiment
Design proposed by the invention is that filter circuit is integrated in the existing circuit in the analog front-end device (for example analog/digital converter or input buffer), to avoid the too big change of do of primary circuit structure and to influence characteristics of signals.In the explanation of Fig. 2, represented that capacitor C can be used as the usefulness of the sampling and the maintenance of analog signal: when switch SW 1 with knowing better, do sample of signal during the SW2 conducting, when turn-offing signal kept, so the inventor can be with capacitor C and switch SW 1, SW2 is considered as the sampling and the holding circuit of analog signal.It should be noted that switch SW 1, SW2 often utilizes transistor (PMOS or NMOS) to be achieved, and because of transistor itself promptly has resistance in essence, so switch SW 1, SW2 can resistance R 1, the R2 equivalence.When switch SW 1, during the SW2 conducting, can be considered resistance R 1, capacitor C is connected with resistance R 2 threes, so sampling and holding circuit also have the effect of filtering this moment, as long as change switch SW 1, the structure of SW2 or capacitor C can possess the filter function of certain specific bandwidth.
For the bandwidth of filter circuit can be regulated according to actual demand, first embodiment utilizes the transistor switch of a plurality of mutual parallel connections to be combined into switch module, select one or more specific transistor switch to come work according to different bandwidth settings, reach the purpose of the multiple high-frequency signal of filtering to cooperate capacitor C.Please refer to Fig. 3, the analog/digital converter 330 that its expression is proposed according to embodiments of the invention one.The filter function of BREATHABLE BANDWIDTH is integrated in sampling and the holding circuit, open and module 310 in comprise 4 transistor switch SW2, SW3, SW4, SW5, the capacitor C of can arranging in pairs or groups produce 4 kinds of different bandwidths (for example 75,150,300, filter effect 500MHz).Switch module 310 is in when design, can which (or which) transistor switch will be connected with capacitor C according to option code decision, to realize above-mentioned 4 kinds of BREATHABLE BANDWIDTH.Option code can be one yard of multiselect (one-of-N code) or thermometer-code (thermometer code) etc., only can select in 4 transistor switches one to connect with capacitor C according to one yard of multiselect is each; Then can utilize the resistance value that 4 transistor switches are combined into to be needed according to thermometer-code, this moment, chosen transistor switch may be one or more.
With 75,150,300, the bandwidth settings of 500MHz is an example, if switch module 310 is designed in according to one yard selection transistor switch of multiselect, can be with transistor switch SW2, SW3, SW4, the length-width ratio design of SW5 was at 1: 2: 4: and 20 ratio (be W/L, 2W/L, 4W/L, 20W/L), only select transistor switch SW2 when bandwidth is 75MHz for use, only select transistor switch SW3 when bandwidth is 150MHz for use, only select transistor switch SW4 when bandwidth is 300MHz for use, only select transistor switch SW5 when bandwidth is 500MHz for use, can set the bandwidth that needs.If switch module 330 is designed in according to thermometer-code and selects transistor switch, can be with transistor switch SW2, SW3, SW4, the length-width ratio design of SW5 was at 1: 1: 2: 16 (is W/L, W/L, 2W/L, ratio 16W/L) is only selected transistor switch SW2 for use when bandwidth is 75MHz, bandwidth is selected transistor switch SW2 during for 150MHz for use, SW3, bandwidth is selected transistor switch SW2, SW3 during for 300MHz for use, SW4, bandwidth is selected transistor switch SW2, SW3, SW4 during for 500MHz for use, SW5 can be combined into the filter effect of different bandwidth by 4 transistor switches.
Certainly, the transistor switch in regulating analog/digital converter can reach the purpose of regulating filtering bandwidth, and the adjusting of input buffer can obtain similar effects equally.Please refer to Fig. 4, the small-signal equivalent circuit of transistor Mp among its expression input buffer IB.By graphic know find out all have the existence of equivalent capacity between the source electrode of transistor Mp, drain electrode, grid, therefore, equally can reach the purpose of regulating bandwidth if regulate transistorized structure.
Please refer to Fig. 5, a kind of input buffer that its expression is proposed according to embodiments of the invention two, it is integrated with the filter function of BREATHABLE BANDWIDTH.Can be on the practice with 4 transistor Mp1, Mp2, Mp3, Mp4 forms transistor modular 510, according to option code (as one yard of multiselect or thermometer-code etc.) determine switch SW3, SW4, SW5, the conducting state of SW6, connecting with current source Io is source follower with one in these transistors (or a plurality of parallel connection is back), to realize the purpose of BREATHABLE BANDWIDTH.Certainly also can reach similar functions, please refer to Fig. 6, the another kind of input buffer that its expression is proposed according to embodiments of the invention two by regulating current source.Current source module 610 can be by 4 current source I1, I2, I3, I4 forms, equally by option code determine switch SW3, SW4, SW5, the conducting state of SW6, connecting with transistor Mp is source follower with one in these current sources (or a plurality of parallel connection is back), when the big more Time Bandwidth of output current of current source is also big more, the total current value becomes positively related proportionate relationship approximately with bandwidth.
The disclosed analog front-end device of the above embodiment of the present invention with BREATHABLE BANDWIDTH filter function, can be integrated in the sampling and holding circuit or input buffer of analog/digital converter, change to circuit is very limited, can not influence the filter function that signal quality is issued to BREATHABLE BANDWIDTH, benefit is very remarkable.
In sum; though the present invention with a preferred embodiment openly as above; right its is not in order to limit the present invention; any those skilled in the art; under the situation that does not break away from the spirit and scope of the present invention; can carry out various changes and modification, so protection scope of the present invention is as the criterion with claims institute restricted portion that is proposed.
Claims (14)
1. the analog/digital converter with BREATHABLE BANDWIDTH filter function is disposed in the analog front-end device of a LCD controller, and so that an analog signal is carried out analog/digital conversion, this analog/digital converter comprises:
One electric capacity is used for sampling and keeps this analog signal; And
One switch module, with this capacitances in series, this switch module comprises a plurality of transistor switches that are connected in parallel to each other, this switch module is selected at least one according to an option code and is made its conducting from described each transistor switch, make this switch module as an equivalent resistance, and form filter circuit by this equivalence resistance and this electric capacity.
2. analog/digital converter as claimed in claim 1, wherein this option code is one yard of a kind of multiselect, makes its conducting in order to select one from described each transistor switch, makes this switch module as this equivalence resistance.
3. analog/digital converter as claimed in claim 1, wherein this option code is a kind of thermometer-code, in order to select one or more its conductings that make from described each transistor switch, makes this switch module as this equivalence resistance.
4. analog/digital converter as claimed in claim 1 also comprises a switch, this switch and this capacitances in series.
5. the input buffer with BREATHABLE BANDWIDTH filter function is disposed in the analog front-end device of a LCD controller, and in order to cushion an analog signal, this input buffer comprises:
One current source; And
One transistor modular, connect to form source follower with this current source, this transistor modular comprises a plurality of transistors that are connected in parallel to each other, this transistor modular is selected at least one according to an option code and is made its conducting from described each transistor, make this transistor modular and this current source form filter circuit.
6. input buffer as claimed in claim 5, wherein this option code is one yard of a kind of multiselect, makes its conducting in order to select one from described each transistor, makes this transistor modular and this current source form filter circuit.
7. input buffer as claimed in claim 5, wherein this option code is a kind of thermometer-code, in order to select one or more its conductings that make from described each transistor, makes this transistor modular and this current source form filter circuit.
8. input buffer as claimed in claim 5, wherein the input of this transistor modular is in series with an impedance.
9. input buffer as claimed in claim 8, wherein this impedance is with in addition equivalence of a transistor switch.
10. the input buffer with BREATHABLE BANDWIDTH filter function is disposed in the analog front-end device of a LCD controller, and in order to cushion an analog signal, this input buffer comprises:
One transistor; And
One current source module, with this transistor series to form source follower, this current source module comprises a plurality of current sources that are connected in parallel to each other, this current source module is selected at least one according to an option code and is made its connection in those current sources, make this current source module and this transistor form filter circuit.
11. input buffer as claimed in claim 10, wherein this option code is one yard of a kind of multiselect, makes its connection in order to select one in those current sources, makes this current source module and this transistor form filter circuit.
12. input buffer as claimed in claim 10, wherein this option code is a kind of thermometer-code, in order to select one or more its connections that make in those current sources, makes this current source module and this transistor form filter circuit.
13. input buffer as claimed in claim 10, wherein this transistorized input is in series with an impedance.
14. input buffer as claimed in claim 13, wherein this impedance is with in addition equivalence of a transistor switch.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031362532A CN100345383C (en) | 2003-05-20 | 2003-05-20 | Analog front end apparatus with adjustable bandwidth wave filtering function |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031362532A CN100345383C (en) | 2003-05-20 | 2003-05-20 | Analog front end apparatus with adjustable bandwidth wave filtering function |
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| Publication Number | Publication Date |
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| CN1549241A CN1549241A (en) | 2004-11-24 |
| CN100345383C true CN100345383C (en) | 2007-10-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNB031362532A Expired - Lifetime CN100345383C (en) | 2003-05-20 | 2003-05-20 | Analog front end apparatus with adjustable bandwidth wave filtering function |
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Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101408571B (en) * | 2007-10-11 | 2011-06-01 | 瑞昱半导体股份有限公司 | Inserted detection circuit |
| CN103178699B (en) * | 2013-02-28 | 2016-03-30 | 广东宽普科技股份有限公司 | Reduce the method for bounce frequency filter consume and adopt the bounce frequency filter of the method |
| CN105071806B (en) * | 2015-08-28 | 2019-01-15 | 西安启微迭仪半导体科技有限公司 | High linearity buffer input signal device applied to high-speed AD converter |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5006854A (en) * | 1989-02-13 | 1991-04-09 | Silicon Systems, Inc. | Method and apparatus for converting A/D nonlinearities to random noise |
| JPH10341159A (en) * | 1997-06-09 | 1998-12-22 | Sony Corp | A/d converter |
| US6118399A (en) * | 1998-03-30 | 2000-09-12 | Silicon Laboratories, Inc. | Coarse/fine switching on digital-to-analog conversion output |
| US20020097177A1 (en) * | 2000-11-29 | 2002-07-25 | Krishnasawamy Nagaraj | System for increasing the bandwidth of sample-and-hold circuits in flash ADCs |
| CN1375936A (en) * | 2001-03-15 | 2002-10-23 | 矽统科技股份有限公司 | A/D converter with low-voltage differential input |
| CN1391353A (en) * | 2001-06-13 | 2003-01-15 | 松下电器产业株式会社 | Sequential comparison A/D converter |
-
2003
- 2003-05-20 CN CNB031362532A patent/CN100345383C/en not_active Expired - Lifetime
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5006854A (en) * | 1989-02-13 | 1991-04-09 | Silicon Systems, Inc. | Method and apparatus for converting A/D nonlinearities to random noise |
| JPH10341159A (en) * | 1997-06-09 | 1998-12-22 | Sony Corp | A/d converter |
| US6118399A (en) * | 1998-03-30 | 2000-09-12 | Silicon Laboratories, Inc. | Coarse/fine switching on digital-to-analog conversion output |
| US20020097177A1 (en) * | 2000-11-29 | 2002-07-25 | Krishnasawamy Nagaraj | System for increasing the bandwidth of sample-and-hold circuits in flash ADCs |
| CN1375936A (en) * | 2001-03-15 | 2002-10-23 | 矽统科技股份有限公司 | A/D converter with low-voltage differential input |
| CN1391353A (en) * | 2001-06-13 | 2003-01-15 | 松下电器产业株式会社 | Sequential comparison A/D converter |
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| CN1549241A (en) | 2004-11-24 |
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