Datenblatt-Suchmaschine für elektronische Bauteile |
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SS7646 Datenblatt(PDF) 11 Page - Silicon Standard Corp. |
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SS7646 Datenblatt(HTML) 11 Page - Silicon Standard Corp. |
11 / 13 page www.SiliconStandard.com 4 of 5 SS7646 8/21/2004 Rev.2.01 Battery Measurement Another feature of the SS7646 is the battery measurement ability. Figure 9 shows a block diagram of a battery voltage monitored by the SS7646. While the main power to the SS7646 via the DC/DC regulator is maintained at the desired voltage, the battery voltage can vary from 0.5V to 6V. The SS7646 is able to monitor this battery voltage through the VBAT pin. The voltage on VBAT pin is divided down by 4 so that the battery voltage of 6V becomes 1.5V to the ADC input. In order to minimize the power consumption, the divider is only on during the sampling phase of the ADC. See Table V for the control bit configurations required to perform this battery measurement. Pressure Measurement The SS7646 is also able to determine the pen or finger touch through the pressure measurement with s o m e s i m ple c a l c u l a t i o n s . T he p r e ss u r e measurement is based on the contact resistance between the X and Y plates. Figure 10 shows a block diagram of the pressure measurement. There are two recommended methods to perform the measurement. Generally, the pressure measurement can be accomplished sufficiently with 8-bit resolution mode, but the following examples are shown with the 12-bit resolution mode. Y+ Y- X+ X- Rtouch Y+ Y- X+ X- Rtouch Measure X-Position Measure Z1-Position Y+ Y- X+ X- Rtouch Measure Z2-Position V V V Figure 10. Block Diagram of Pressure Measurement (1) The first method requires the user knowing the X-plate resistance. Performing three touch screen conversions, X-Position, Z1-Position and Z2-position, then use the following equation to calculate the touch resistance: (2) The second method requires the user knowing both the X-plate and Y-plate resistance. Performing three touch screen conversions, X-Position, Y-Position and Z1-position, then use the following equation to calculate the touch resistance: Pen Interrupt Request The pen interrupt function is shown in Figure 11. Normally the /PENIRQ is HIGH by connecting a pull-up resistor (typically 100KΩ) to VDD. If /PENIRQ has been enabled (See Table V), Y- driver is ON and connected to GND and /PENIRQ diode is connected to X+ input. When the touch screen connected to the SS7646 is touched, the X+ input is pulled to ground through the touch screen and /PENIRQ will go low, initiating an interrupt to the microprocessor. During the X and Y plates measurement cycles, the /PENIRQ diode will be internally connected to GND and X+ input disconnected from the diode to eliminate leakage current to the touch screen. Y+ Y- X+ /PENIRQ ENABLE VDD 100K /PENIRQ Figure 11. Block Diagram of Pen Interrupt Circuit []1 ) − = 1 2 position xplate touch Z (Z x ) 4096 (X x R R [] 4096 ) x Y R ( - Z (4096 x 4096 ) X x R ( R position yplate 1 position xplate touch 1 ) − = |
Ähnliche Teilenummer - SS7646 |
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Ähnliche Beschreibung - SS7646 |
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