EVAL-AD7877EBZ Analog Devices Inc, EVAL-AD7877EBZ Datasheet
EVAL-AD7877EBZ
Specifications of EVAL-AD7877EBZ
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EVAL-AD7877EBZ Summary of contents
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FEATURES 4-wire touch screen interface LCD noise reduction feature (STOPACQ pin) Automatic conversion sequencer and timer User-programmable conversion parameters On-chip temperature sensor: −40°C to +85°C On-chip 2.5 V reference On-chip 8-bit DAC 3 auxiliary analog inputs 1 dedicated and 3 ...
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AD7877 TABLE OF CONTENTS Features .............................................................................................. 1 Applications ....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications ..................................................................................... 3 Timing Specifications .................................................................. 5 Timing Diagrams .......................................................................... 5 Absolute Maximum Ratings ............................................................ 6 ESD ...
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SPECIFICATIONS 2.5 V internal or external REF Table 1. Parameter Min DC ACCURACY Resolution 12 No Missing Codes 11 1 Integral Nonlinearity (INL) 1 Differential Nonlinearity (DNL) Negative DNL ...
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AD7877 Parameter Min DAC Resolution Integral Nonlinearity Differential Nonlinearity Voltage Mode Output Voltage Range Slew Rate Output Settling Time Capacitive Load Stability Output Impedance Short-Circuit Current Current Mode Output Current Range 0 Output Impedance LOGIC INPUTS Input High Voltage, V ...
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TIMING SPECIFICATIONS unless otherwise noted MIN MAX signals are specified with (10 Table 2. Parameter Limit ...
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AD7877 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 V to GND ...
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PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS BAT2 2 BAT1 3 AD7877 AUX3/GPIO3 4 TOP VIEW (Not to Scale) AUX2/GPIO2 5 AUX1/GPIO1 ...
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AD7877 Pin No. Mnemonic Description 28 V Logic Power Supply Input. The voltage supplied at this pin determines the operating voltage for the serial DRIVE interface of the AD7877. 29 ARNG When the DAC is in current output mode, a ...
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TYPICAL PERFORMANCE CHARACTERISTICS T = 25° REF SAMPLE 800 ADC, REF, AND DAC 700 ADC AND REF 600 500 –50 –30 – TEMPERATURE (°C) Figure 6. Supply ...
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AD7877 1.0 0.8 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 0 500 1000 1500 2000 2500 CODE Figure 12. ADC DNL Plot ...
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TEMPERATURE ( ° C) Figure 18. ADC Code vs. Temperature (2.7 V Supply) 1183 1182 1181 1180 1179 1178 1177 1176 2.7 2.8 ...
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AD7877 TEMPERATURE = 25°C 1 CH1 200mV CH2 100mV M2.00μs Figure 24. DAC Output Settling Time (Zero Scale to Half Scale) 600 500 400 DAC SINK CURRENT 300 200 100 NOTE: MAXIMUM DAC SINK CURRENT IS ...
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TERMINOLOGY Integral Nonlinearity (INL) 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 at 1 LSB below the first code transition, and full scale ...
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AD7877 CIRCUIT INFORMATION The AD7877 is a complete, 12-bit data acquisition system for digitizing positional inputs from a touch screen in PDAs and other devices. In addition, it can monitor two battery voltages, ambient temperature, and three auxiliary analog voltages, ...
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X– Y+ Y– AUX1/GPIO2 I/P MUX AUX2/GPIO3 AUX3/GPIO4 IN+ BAT1 BAT2 TEMPERATURE SENSOR Figure 28. Analog Input Structure The AD7877 can be set up to automatically convert either specific input channels or a sequence ...
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AD7877 For greater accuracy, the ratiometric method has two significant advantages: • The reference to the ADC is provided from the actual voltage across the screen; therefore, when the voltage drops across the switches, it has no effect. • Because ...
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It is only during the sample or acquisition phase of the ADC operation of the AD7877 that noise from the LCD screen has an effect on the ADC measurements. During the hold or conversion phase, the noise has no effect, ...
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AD7877 Temperature Calculations If an explicit temperature reading in °C is required, then this is calculated as follows for the single measurement method: 1. Calculate the scale factor of the ADC in degrees per LSB: Degrees per LSB = ADC ...
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AUXILIARY INPUTS The AD7877 has three auxiliary analog inputs, AUX1 to AUX3. These channels have a full-scale input range from The ADC channel addresses for AUX1 to AUX3 are 0011b, 0100b, and 0101b, and the results ...
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AD7877 CONTROL REGISTERS Control Register 1 contains the ADC channel address, the SER/ DFR bit (to choose single or differential methods of touch screen measurement), the register read address, and the ADC mode bits. Control Register 1 should always be ...
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Table 6. Codes for Selecting Input Channel and Normal or Ratiometric Conversion SER/DFR Channel CHADD(3: ...
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AD7877 STOPACQ Polarity (Control Register 2, Bit[3]) This bit should be set according to the polarity of the signal applied to the STOPACQ pin. If that signal is active high, that is, no acquisitions should occur during the high period ...
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HOST PROGRAMS AD7877 IN MODE 01 IS FCD NO REQUIRED? YES START FCD TIMER IS FCD FINISHED? NO YES YES IS STOPACQ SIGNAL ACTIVE? NO START ACQUISITION TIMER IS STOPACQ YES SIGNAL ACTIVE ACQUISITION TIME FINISHED? YES ...
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AD7877 HOST PROGRAMS AD7877 IN MODE 11 VALID NO SEQUENCE MODE 00 YES IS NO SCREEN TOUCHED? YES SELECT NEXT CHANNEL IS FCD NO REQUIRED? YES START FCD TIMER IS FCD NO FINISHED? YES YES IS STOPACQ ...
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MHz (maximum), then t DCLK DCLK t = 512 μs with timer set to 1024 (TMR bits = 01b CLK period × t WRITE READ DCLK t = maximum time ...
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AD7877 8-BIT DAC The AD7877 features an on-chip 8-bit DAC for LCD contrast control. The DAC can be configured for voltage output by clearing Bit 2 of the DAC register (Address 1110b), or for current output by setting this bit. ...
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When the DAC output voltage is zero, it sinks the maximum current through R1. The feedback current and, therefore, V are at their maximum. As the DAC output voltage increases, the sink current and, thus, the feedback current decrease, and ...
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AD7877 SERIAL INTERFACE The AD7877 is controlled via a 3-wire serial peripheral interface (SPI). The SPI has a data input pin (DIN) for inputting data to the device, a data output pin (DOUT) for reading data back from the device, ...
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WRITE TIMING No serial interface operations can take place when CS is high. To write to the AD7877, CS must be taken low. To write to the device, a burst of 16 clock pulses is input to DCLK while the ...
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AD7877 GENERAL-PURPOSE I/O PINS The AD7877 has one dedicated general-purpose logic input/ output pin (GPIO4), and any or all of the three auxiliary analog inputs can also be reconfigured as GPIOs. Associated with the GPIOs are two 8-bit control registers ...
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If the ALERT source is a GPIO, then masking out the interrupt by clearing the corresponding ALEN bit removing the source of the interrupt on the GPIO pin causes ALERT to go high again. If the ALERT ...
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AD7877 GROUNDING AND LAYOUT It is recommended that the ground pins, AGND and DGND, be shorted together as close as possible to the device itself on the user’s PCB. For more information on grounding and layout considerations for the AD7877, ...
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REGISTER MAPS Table 13. Write Register Map Register Address Binary WADD3 WADD2 WADD1 WADD0 ...
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AD7877 Table 15. Read Register Map Register Address Binary RADD4 RADD3 RADD2 RADD1 ...
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DETAILED REGISTER DESCRIPTIONS Register Name: Control Register 1 Write Address: 0001 Read Address: 00001 Default Value: 0x000 Type: Read/write Table 16. Bit Name Read/Write Description 0 MODE0 R/W LSB of ADC mode code 1 MODE1 R/W MSB of ADC mode ...
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AD7877 Register Name: Control Register 2 Write Address: 0010 Read Address: 00010 Default Value: 0x000 Type: Read/write Table 17. Bit Name Read/Write Description 0 TMR0 R/W LSB of conversion interval timer 1 TMR1 R/W MSB of conversion interval timer 00 ...
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Register Name: Alert Status/Enable Register Write Address: 0011 Read Address: 00011 Default Value: 0x000 Type: Read/write Table 18. Bit Name Read/Write Description 0 AUX1LO R/W When this bit is 1, the AUX1 channel is below its low limit 1 BAT1LO ...
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AD7877 Register Name: BAT2 Low Limit Write Address: 1001 Read Address: 01001 Default Value: 0x000 Type: Read/write This register contains the 12-bit low limit for Battery Monitoring Input 2. Register Name: TEMP1 Low Limit Write Address: 1010 Read Address: 01010 ...
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Register Name: Sequencer Register 0 Write Address: 1100 Read Address: 01100 Default Value: 0x000 Type: Read/write Table 19. Bit Name Read/Write Description 0 Not Used R/W This bit is not used 1 Z1_SS R/W Setting this bit includes the Z1 ...
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AD7877 Register Name: DAC Register Write Address: 1110 Read Address: 01110 Default Value: 0x008 Type: Read/write Table 21. Bit Name Read/Write 0 RANGE R/W 1 Not Used R/W 2 V/I R R/W 4 DAC0 5 DAC1 6 DAC2 ...
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Register Name: AUX2 Write Address: N/A Read Address: 10100 Default Value: 0x000 Type: Read only This register contains the 12-bit result of the measurement at Auxiliary Input 2. Register Name: AUX3 Write Address: N/A Read Address: 10101 Default Value: 0x000 ...
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AD7877 GPIO REGISTERS GPIO registers are written to using an extended 8-bit address. The first four bits of the data-word are always 1111b to access the extended writing map. The next four bits are the register address. This leaves 8 ...
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Register Name: GPIO Control Register 2 Write Address: [1111] 0001 Read Address: 11100 Default Value: 0x000 Type: Read/write Table 23. Bit Name Read/Write 0 GPIO4_ALEN R/W 1 GPIO4_DIR R/W 2 GPIO4_POL R/W 3 Not Used 4 GPIO3_ALEN R/W 5 GPIO3_DIR ...
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... AD7877ACPZ-500RL7 −40°C to +85°C 1 AD7877ACBZ-REEL −40°C to +85°C 1 AD7877ACBZ-REEL7 −40°C to +85°C 1 EVAL-AD7877EBZ RoHS Compliant Part. ©2004–2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 5.00 BSC SQ 0.60 MAX 24 ...