Electronic Components Datasheet Search |
|
TSC2046IPWRG4 Datasheet(PDF) 11 Page - Burr-Brown (TI) |
|
|
TSC2046IPWRG4 Datasheet(HTML) 11 Page - Burr-Brown (TI) |
11 / 23 page TSC2046 11 SBAS265C www.ti.com always a percentage of the external resistance, regardless of how it changes in relation to the on-resistance of the internal switches. Note that there is an important consideration regarding power dissipation when using the ratiometric mode of operation (see the Power Dissipation section for more details). As a final note about the differential reference mode, it must be used with +VCC as the source of the +REF voltage and cannot be used with VREF. It is possible to use a high- precision reference on VREF and single-ended reference mode for measurements which do not need to be ratiometric. In some cases, it is possible to power the converter directly from a precision reference. Most references can provide enough power for the TSC2046, but might not be able to supply enough current for the external load (such as a resistive touch screen). TOUCH SCREEN SETTLING In some applications, external capacitors may be required across the touch screen for filtering noise picked up by the touch screen (e.g., noise generated by the LCD panel or backlight circuitry). These capacitors provide a low-pass filter to reduce the noise, but cause a settling time requirement when the panel is touched that typically shows up as a gain error. There are several methods for minimizing or eliminating this issue. The problem is the input and/or reference has not settled to the final steady-state value prior to the ADC sampling the input(s) and providing the digital output. Additionally, the reference voltage may still be changing during the measure- ment cycle. Option 1 is to stop or slow down the TSC2046 DCLK for the required touch screen settling time. This allows the input and reference to have stable values for the Acquire period (3 clock cycles of the TSC2046; see Figure 9). This works for both the single-ended and the differential modes. Option 2 is to operate the TSC2046 in the differential mode only for the touch screen measurements and command the TSC2046 to remain on (touch screen drivers ON) and not go into power-down (PD0 = 1). Several conversions are made depending on the settling time required and the TSC2046 data rate. Once the required number of conversions have been made, the processor commands the TSC2046 to go into its power-down state on the last measurement. This process is required for X-Position, Y-Position, and Z-Position measure- ments. Option 3 is to operate in the 15 Clock-per-Conversion mode, which overlaps the analog-to-digital conversions and maintains the touch screen drivers on until commanded to stop by the processor (see Figure 13). TEMPERATURE MEASUREMENT In some applications, such as battery recharging, a measure- ment of ambient temperature is required. The temperature measurement technique used in the TSC2046 relies on the characteristics of a semiconductor junction operating at a fixed current level. The forward diode voltage (VBE) has a well-defined characteristic versus temperature. The ambient temperature can be predicted in applications by knowing the +25°C value of the VBE voltage and then monitoring the delta of that voltage as the temperature changes. The TSC2046 offers two modes of operation. The first mode requires calibration at a known temperature, but only requires a single reading to predict the ambient temperature. A diode is used (turned on) during this measurement cycle. The voltage across the diode is connected through the MUX for digitizing the forward bias voltage by the ADC with an address of A2 = 0, A1 = 0, and A0 = 0 (see Table I and Figure 6 for details). This voltage is typically 600mV at +25°C with a 20µA current through the diode. The absolute value of this diode voltage can vary a few millivolts. However, the TC of this voltage is very consistent at –2.1mV/°C. During the final test of the end product, the diode voltage would be stored at a known room temperature, in memory, for calibration pur- poses by the user. The result is an equivalent temperature measurement resolution of 0.3°C/LSB (in 12-bit mode). FIGURE 6. Functional Block Diagram of Temperature Mea- surement Mode. ADC MUX TEMP0 TEMP1 +V CC The second mode does not require a test temperature calibra- tion, but uses a two-measurement method to eliminate the need for absolute temperature calibration and for achieving 2°C accuracy. This mode requires a second conversion with an address of A2 = 1, A1 = 1, and A0 = 1, with a 91 times larger current. The voltage difference between the first and second conversion using 91 times the bias current is represented by kT/q • ln (N), where N is the current ratio = 91, k = Boltzmann’s constant (1.38054 • 10–23 electron volts/ degrees Kelvin), q = the electron charge (1.602189 • 10–19 C), and T = the temperature in degrees Kelvin. This method can provide improved absolute temperature measurement over the first mode at the cost of less resolution (1.6°C/LSB). The equation for solving for °K is: °K = q • ∆V/(k • ln (N)) (1) where, ∆V = V (I91) – V (I1) (in mV) ∴ °K = 2.573 °K/mV • ∆V °C = 2.573 • ∆V(mV) – 273°K NOTE: The bias current for each diode temperature mea- surement is only on for 3 clock cycles (during the acquisition mode) and, therefore, does not add any noticeable increase in power, especially if the temperature measurement only occurs occasionally. |
Similar Part No. - TSC2046IPWRG4 |
|
Similar Description - TSC2046IPWRG4 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |