Signal conversion control circuit for touch screen and method thereof

• US 8,711,107 B2
• Filed: 04/20/2009
• Issued: 04/29/2014
• Est. Priority Date: 10/29/2008
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Myson Century, Inc.
• Inventors: Fann, Kee Lih, Zhang, Fang
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Nadkarni, Sarvesh J
• Application Number:
  US12/426,573
• Publication Number:
  US 20100103120A1
• Time in Patent Office: 1,835 Days
• Field of Search: 345/173
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184

Abstract

A signal conversion control circuit comprises an analog-to-digital converter, a first sample-and-hold circuit, a second sample-and-hold circuit, a first switch, a second switch, a third switch, and a fourth switch. The analog-to-digital converter has an input end for receiving an output signal of a touch screen. The first sample-and-hold circuit is configured to provide the analog-to-digital converter with a high-level reference voltage. The second sample-and-hold circuit is configured to provide the analog-to-digital converter with a low-level reference voltage. The first switch connects a supplied voltage to the touch screen. The second switch connects the touch screen to a ground potential. The third switch connects the supplied voltage to the first sample-and-hold circuit through the first switch. The fourth switch connects the ground potential to the second sample-and-hold circuit through the second switch.

Claims

1. A signal conversion control circuit applied to a touch screen, comprising:

an analog-to-digital converter having an input end for receiving an output signal of a touch screen;

a first sample-and-hold circuit configured to provide the analog-to-digital converter with a high-level reference voltage;

a second sample-and-hold circuit configured to provide the analog-to-digital converter with a low-level reference voltage;

a first switch connecting a supplied voltage to the touch screen;

a second switch connecting the touch screen to a ground potential;

a third switch connecting the supplied voltage to the first sample-and-hold circuit through the first switch; and

a fourth switch connecting the ground potential to the second sample-and-hold circuit through the second switch;

wherein the first sample-and-hold circuit includes a first operational amplifier and a capacitor and a non-inverting input terminal of the first operational amplifier is connected to the third switch and the capacitor, an inverting input terminal of the first operational amplifier is connected to an output terminal of the first operational amplifier, and an output terminal of the first operational amplifier is connected to a high-level reference voltage terminal of the analog-to-digital converter.

2. The signal conversion control circuit of claim 1, wherein input and output components of the first operational amplifier are implemented by an N-type transistor, and an active load of the first operational amplifier is implemented by a P-type transistor.

3. The signal conversion control circuit of claim 1, wherein the second sample-and-hold circuit includes a second operational amplifier and a capacitor.

4. The signal conversion control circuit of claim 3, wherein input and output components of the second operational amplifier are implemented by a P-type transistor, and an active load of the second operational amplifier is implemented by an N-type transistor.

5. The signal conversion control circuit of claim 3, wherein a non-inverting input terminal of the second operational amplifier is connected to the fourth switch and the capacitor, an inverting terminal of the second operational amplifier is connected to an output terminal of the second operational amplifier, and the output terminal is connected to a low-level reference voltage terminal of the analog-to-digital converter.

6. The signal conversion control circuit of claim 1, further comprising a third sample-and-hold circuit configured to provide the analog-to-digital converter with output sampled signals of the touch screen.

7. The signal conversion control circuit of claim 1, which is applied to a four-wire or a five-wire touch screen.