AD7873 Analog Devices, AD7873 Datasheet
AD7873
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AD7873 Summary of contents
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... GENERAL DESCRIPTION The AD7873 is a 12-bit successive approximation ADC with a synchronous serial interface and low on resistance switches for driving touch screens. The AD7873 operates from a single 2 5.25 V power supply and features throughput rates greater than 125 kSPS. The AD7873 features direct battery measurement, temperature measurement, and touch pressure measurement ...
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... AD7873 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Product Highlights ........................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Specifications .................................................................. 5 Absolute Maximum Ratings............................................................ 6 Thermal Resistance ...................................................................... 6 ESD Caution.................................................................................. 6 Pin Configurations and Function Descriptions ........................... 7 Terminology ...................................................................................... 8 Typical Performance Characteristics ............................................. 9 REVISION HISTORY 9/06—Rev Rev. E Changes to Figure 13 Caption....................................................... 10 Updated Outline Dimensions ...
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... V min 0.4 0.4 V max ±1 ±1 μA max max Rev Page AD7873 Test Conditions/Comments + External reference CS = GND typically 260 Ω when the CC on-board reference is enabled Sampling; 1 GΩ when battery monitor is off External reference Internal reference Typically 10 nA, V ...
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... Temperature range as follows Versions: –40°C to +85°C. 2 See the Terminology section. 3 Difference between TEMP0 and TEMP1 measurement. No calibration necessary. 4 Temperature drift is –2.1 mV/°C. 5 Sample tested @ 25°C to ensure compliance. 6 See the Power vs. Throughput Rate section. 1 AD7873A AD7873B Unit V – 0.2 V – 0.2 V min CC CC 0.4 0.4 V max 0.4 ...
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... CS rising edge to DOUT high impedance ns max 200µ OUTPUT PIN C L 50pF 200µ Figure 2. Load Circuit for Digital Output Timing Specifications Rev Page and timed from a voltage level of 1 quoted in the timing characteristics is the true bus relinquish 12 1.6V AD7873 ...
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... AD7873 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter +V to GND CC Analog Input Voltage to GND Digital Input Voltage to GND Digital Output Voltage to GND V to GND REF Input Current to Any Pin Except Supplies Operating Temperature Range Commercial (A, B Versions) Storage Temperature Range ...
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... CS is high. BUSY Output. Logic output. This output is high impedance when CS is high. Data In. Logic Input. Data to be written to the AD7873 control register is provided on this input and is clocked into the register on the rising edge of DCLK (see the Control Register section). ...
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... AD7873 TERMINOLOGY Integral Nonlinearity Integral nonlinearity is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. The endpoints of the transfer function are zero scale, a point 1 LSB below the first code transition, and full scale, a point 1 LSB above the last code transition. ...
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... TEMPERATURE (°C) Figure 8. Power-Down Supply Current vs. Temperature 1000 V 100 2.2 2.7 3.2 3.7 4.2 +V (V) CC Figure 9. Maximum Sample Rate vs. +V 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –40 – TEMPERATURE (°C) Figure 10. Change in Offset vs. Temperature AD7873 80 100 = +V REF CC 4.7 5 100 ...
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... AD7873 7.5 6.5 5.5 4.5 3.5 2.5 1.5 0 SAMPLE RATE (kHz) Figure 11. Reference Current vs. Sample Rate X– 6 Y– 2.0 2.5 3.0 3.5 4.0 +V (V) CC Figure 12. Switch On Resistance vs. +V (X+, Y Pin; X−, Y−: Pin to GND) CC 2.0 1.8 1.6 1.4 1.2 INL 500Ω 1.0 0.8 DNL 2kΩ 0.6 0.4 DNL 500Ω 0 ...
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... Figure 21. TEMP0 Diode Voltage vs 100 120 0 3.6 (25°C) Figure 22. Auxiliary Channel Dynamic Performance Rev Page AD7873 1µF CAP (1800µs) SETTLING TIME 200 400 600 800 1000 1200 1400 1600 TURN-ON TIME (µs) Figure 20. Internal V vs. Turn-on Time REF 2 ...
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... Figure 23. AC PSRR vs. Supply Ripple Frequency Figure 23 shows the power supply rejection ratio vs. V frequency for the AD7873. The power supply rejection ratio is defined as the ratio of the power in the ADC output at full-scale frequency the power of a 100 mV sine wave applied to the ...
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... The AD7873 can be operated from a 2 5.25 V supply. When operated from either supply supply, the AD7873 is capable of throughput rates of 125 kSPS when provided with a 2 MHz clock. The AD7873 provides the user with on-chip track-and-hold, ...
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... AD7873 ANALOG INPUT Figure 26 shows an equivalent circuit of the analog input structure of the AD7873 that contains a block diagram of the input multiplexer, the differential input of the ADC, and the differential reference. Table 6 shows the multiplexer address corresponding to each analog input, both for the SER/ DFR bit in the control register set high and low ...
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... AD7873 data rate. Once the required number of conversions have been made, the AD7873 can then be placed in a power-down state on the last measurement. The last method is to use the 15-DCLK cycle mode, maintaining the touch screen drivers on until it is commanded by the processor to stop ...
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... AD7873 the AD7873 is approximately 70 Ω. In this mode of operation, therefore, some voltage is likely to be lost across the internal switches, and it is unlikely that the internal switch resistance will track the resistance of the touch screen over temperature and supply, providing an additional source of error. ...
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... Battery Measurement The AD7873 can monitor a battery voltage from Figure 31 shows a block diagram of a battery voltage monitored through the V pin. The voltage to the +V BAT maintained at the desired supply voltage via the dc-to-dc regulator while the input to the regulator is monitored. This ...
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... CMOS logic open-drain output, the PENIRQ output remains high normally. If PENIRQ is enabled (see Table 8), when the touch screen connected to the AD7873 is touched by a pen or finger, the PENIRQ output goes low, initiating an interrupt to a microprocessor. This can then instruct a control word to be written to the AD7873 to initiate a conversion ...
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... Table PD1, PD0 Power Management Bits. These two bits decode the power-down mode of the AD7873 as shown in Table 8. screen. In single-ended mode, the reference voltage to the converter is always the difference between the V pins. See Table 6 and Figure 26 through Figure 29 for further information ...
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... THROUGHPUT (kSPS) Figure 35. Supply Current vs. Throughput (μA) For example, if the AD7873 is operated in a 24-DCLK continuous sampling mode, with a throughput rate of 10 kSPS and a DCLK of 2 MHz, and the device is placed in the power-down mode between conversions, (PD0, PD1 = 0, 0), that is, the ADC shuts ...
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... Figure 36 shows the typical operation of the serial interface of the AD7873. The serial clock provides the conversion clock and also controls the transfer of information to and from the AD7873. One complete conversion can be achieved with 24 DCLK cycles. The CS signal initiates the data transfer and conversion process. ...
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... AD7873 is not as critical, because settling to eight bits is all that is required. The clock rate can be as much as 50% faster. The faster clock rate and fewer clock cycles combine to provide double the conversion rate ...
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... GROUNDING AND LAYOUT For information on grounding and layout considerations for the AD7873, refer to Application Note AN-577, Layout and Grounding Recommendations for Touch Screen Digitizers. PCB DESIGN GUIDELINES FOR CHIP SCALE PACKAGE The lands on the chip scale package (CP-32) are rectangular. The printed circuit board pad for these should be 0.1 mm longer than the package land length and 0 ...
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... AD7873 OUTLINE DIMENSIONS 0.197 0.193 0.189 16 9 0.158 0.154 0.244 0.150 1 0.236 8 0.228 PIN 1 0.069 0.065 0.053 0.049 0.010 0.025 0.012 0.004 SEATING BSC 0.008 PLANE COPLANARITY 0.004 COMPLIANT TO JEDEC STANDARDS MO-137-AB Figure 40. 16-Lead Shrink Small Outline Package [QSOP] (RQ-16) Dimensions shown in inches ...
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... AD7873ARUZ-REEL7 –40°C to +85°C AD7873ACP –40°C to +85°C AD7873ACP-REEL –40°C to +85°C AD7873ACP-REEL7 –40°C to +85°C 3 AD7873ACPZ –40°C to +85°C 3 AD7873ACPZ-REEL –40°C to +85°C 3 AD7873ACPZ-REEL7 –40°C to +85°C AD7873BCP –40°C to +85°C AD7873BCP-REEL – ...
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... AD7873 NOTES Rev Page ...
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... NOTES Rev Page AD7873 ...
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... AD7873 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C02164-0-9/06(E) T Rev Page ...