TSC2101-Audio Codec w/ Integrated Headphone Speaker Amp ...

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SLAS392C− JUNE 2003 − REVISED SEPTEMBER 2004www.ti.comBattery0.5 to 6 V+−LDO or DC-DCConverter3.0 V to 3.6 VVDDRVBAT8 kΩ2 kΩADCFigure 33. Battery Measurement Functional Block DiagramBattery measurement can only be done in host−controlled mode.See the section Conversion Time Calculation for the TSC2101 and subsection Non Touch MeasurementOperation in this data sheet for timing diagrams and conversion time calculations.For increased protection and robustness, TI recommends a minimum 100−Ω resistor be added in seriesbetween the system battery and the VBAT pin. The 100-Ω resistor will cause an approximately 1% gain changein the battery voltage measurement, which can easily be corrected in software when the battery conversion datais read by the operating system.Auxiliary MeasurementThe auxiliary voltage inputs (AUX1 and AUX2) can be measured in much the same way as the battery inputsexcept the difference that input voltage is not divided. Applications might include external temperature sensing,ambient light monitoring for controlling the backlight, or sensing the current drawn from the battery. The auxiliaryinput can also be monitored continuously in scan mode.The TSC2101 provides feature to measure resistance using auxiliary inputs. It has two modes of operation:(1) External bias resistance measurement (2) Internal bias resistance measurement. Internal bias resistancemeasurement mode does not need an external bias resistance of 50 kΩ, but provides less accuracy becauseof on chip resistance variation, which is typically ±20%. Figure 34 shows connection diagram for resistancemeasurement mode on AUX1.VREFVREF50 kΩ50 kΩ50 kΩAUX1VsarSARAUX1VsarSARRRa. Internal bias, Resistance Measurementb. External bias, Resistance MeasurementFigure 34. Connection DIagram for Resistance MeasurementResistance can be calculated using following formula:R 50 K VsarVREF Vsar42
www.ti.comSLAS392C− JUNE 2003 − REVISED SEPTEMBER 2004Where:VREF is the SAR ADC referenceVsar is input to the SAR ADCThe TSC2101 supports programmable auto−auxiliary measurement mode, which can be enabled using controlregister 0CH/page 1. In this mode, the TSC2101 can auto start the auxiliary measurement after aprogrammable interval. The user can program minimum and maximum threshold values through a register. Ifthe measurement goes outside the threshold range, the TSC2101 sets a flag in the read only control register0CH/page 1, which gets cleared after the flag is read. The TSC2101 can also be configured to send an activehigh interrupt over GPIO1 by setting D9 of control register 0CH/page 1. The duration of the interrupt isapproximately 2 ms.Auxiliary measurement can only be done in host−controlled mode.See the section Conversion Time Calculation for the TSC2101 and subsection Non Touch MeasurementOperation in this data sheet for timing diagram and conversion time calculationPort ScanIf making measurements of VBAT, AUX1, and AUX2 is desired on a periodic basis, the Port Scan mode canbe used. This mode causes the TSC2101 to sample and convert battery input and both auxiliary inputs. At theend of this cycle, the battery and auxiliary result registers contain the updated values. Thus, with one write tothe TSC2101, the host can cause three different measurements to be made.Port Scan can only be done in host-controlled mode. See the section Issues at the end of this data sheet fordetails of a known issue with this mode.See the section Conversion Time Calculation for the TSC2101 and subsection Port Scan Operation in this datasheet for timing diagrams and conversion time calculations.Buffer ModeThe TSC2101 supports a programmable buffer mode, which is applicable for both touch screen relatedconversion (X, Y, Z1, Z2) and nontouch screen related conversion (BAT, AUX1, AUX2, TEMP1, TEMP2). Buffermode is implemented using a circular FIFO with a depth of 64. The number of interrupts required to be servicedby a host processor can be reduced significantly buffer mode. Buffer mode can be enabled using control register02H/page1.Figure 35. Circular Buffer43
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