AD7873ARUZ ,Touch Screen Digitizerfeatures on-board switches. This, coupled with low reference off, or 2.41 mW typ with the reference ..
AD7873BRQ ,Touch Screen Digitizerfeatures direct battery measurement, temperature measurement, and touch-pressure measurement. The ..
AD7874AN ,LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition Systemspecifications is not implied. Exposure to absolutemaximum rating conditions for extended periods m ..
AD7874AQ ,LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition SystemFEATURESFUNCTIONAL BLOCK DIAGRAMFour On-Chip Track/Hold AmplifiersSimultaneous Sampling of 4 Channe ..
AD7874AQ ,LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition SystemSpecifications in bold print are 100% production tested. All other times are sample tested at +25°C ..
AD7874AR ,LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition SystemSpecifications subject to change without notice.1.6mAABSOLUTE MAXIMUM RATINGS*(T = +25°C unless oth ..
ADM3222 ,High-Speed, +3.3V, 2-Channel RS232/V.28 Interface Device with 460kBPS Data Rate and Shutdown and Enable PinsCHARACTERISTICSOperating Voltage Range 3.0 3.3 5.5 VV Power Supply Current 1.3 3 mA No LoadCC812 mA ..
ADM3222AN ,Low Power, +3.3 V, RS-232 Line Drivers/Receiversspecifications and operates at data ratesup to 460 kbps.R1 R1R1OUT INCMOSEIA/TIA-232OUTPUTSFour ext ..
ADM3222ARS ,Low Power, +3.3 V, RS-232 Line Drivers/Receiversspecifications T to T unless otherwise noted.)CC MIN MAXParameter Min Typ Max Unit Test Conditions/ ..
ADM3222ARU ,Low Power, +3.3 V, RS-232 Line Drivers/Receiversspecifications T to T unless otherwise noted.)CC MIN MAXParameter Min Typ Max Unit Test Conditions/ ..
ADM3222ARU-REEL , Low Power, 3.3 V, RS-232 Line Drivers/Receivers
ADM3222ARUZ-REEL , Low Power, 3.3 V, RS-232 Line Drivers/Receivers
AD7873ARUZ
Touch Screen Digitizer
Touch Screen DigitizerRev. D
FEATURES
4-wire touch screen interface
On-chip temperature sensor: −40°C to +85°C
On-chip 2.5 V reference
Direct battery measurement (0 V to 6 V)
Touch-pressure measurement
Specified throughput rate of 125 kSPS
Single supply, VCC of 2.2 V to 5.25 V
Ratiometric conversion
High speed serial interface
Programmable 8-bit or 12-bit resolution
One auxiliary analog input
Shutdown mode: 1 µA max
16-lead QSOP, TSSOP, and LFCSP packages
APPLICATIONS
Personal digital assistants
Smart hand-held devices
Touch screen monitors
Point-of-sale terminals
Pagers
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 2.2 V
to 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. The AD7873
also has an on-board reference of 2.5 V that can be used for the
auxiliary input, battery monitor, and temperature measurement
modes. When not in use, the internal reference can be shut
down to conserve power. An external reference can also be
applied and can be varied from 1 V to VCC, while the analog
input range is from 0 V to VREF. The device includes a shutdown
mode that reduces the current consumption to less than 1 µA.
The AD7873 features on-board switches. This, coupled with low
power and high speed operation, makes the device ideal for
battery-powered systems such as personal digital assistants with
resistive touch screens and other portable equipment. The part
is available in a 16-lead 0.15" quarter size outline package
(QSOP), a 16-lead thin shrink small outline package (TSSOP),
and a 16-lead lead frame chip scale package (LFCSP).
FUNCTIONAL BLOCK DIAGRAM 02164-D-001
AD7873
+VCC
+VCC
PENIRQ
SPORT
DINCSDOUTDCLKBUSY
SAR + ADCCONTROL LOGIC
6-TO-1I/PMUX
GND
BATTERY
MONITOR
AUX
2.5V
REF
VREFFigure 1.
PRODUCT HIGHLIGHTS 1. Ratiometric conversion mode available, eliminating errors
due to on-board switch resistances.
2. On-board temperature sensor: −40°C to +85°C.
3. Battery monitor input.
4. Touch-pressure measurement capability.
5. Low power consumption of 1.37 mW max with the
reference off, or 2.41 mW typ with the reference on, at
125 kSPS and VCC at 3.6 V.
6. Package options include 4 mm × 4 mm LFCSP.
7. Analog input range from 0 V to VREF.
8. Versatile serial I/O ports.
TABLE OF CONTENTS Specifications.....................................................................................3
Timing Specifications..................................................................5
Absolute Maximum Ratings............................................................6
ESD Caution..................................................................................6
Pin Configurations and Function Descriptions...........................7
Terminology......................................................................................8
Typical Performance Characteristics.............................................9
Circuit Information........................................................................13
ADC Transfer Function.............................................................13
Typical Connection Diagram...................................................13
Analog Input...............................................................................14
Measurements.............................................................................16
Pen Interrupt Request................................................................18
Control Register.........................................................................19
Power vs. Throughput Rate.......................................................20
Serial Interface............................................................................21
Grounding and Layout..................................................................23
PCB Design Guidelines for Chip Scale Package....................23
Outline Dimensions.......................................................................24
Ordering Guide..........................................................................25
REVISION HISTORY
6/04—Changed from Rev. C to Rev. D Updated Format..................................................................Universal
Changes to Absolute Maximum Ratings.......................................6
Additions to PD0 and PD1 Description......................................21
PBC Guidelines for Chip Scale Package Added.........................23
Additions to Ordering Guide........................................................25
4/03—Changed from Rev. B to Rev. C Changes to Formatting......................................................Universal
Updated Outline Dimensions.......................................................19
1/02—Changed from Rev. A to Rev. B Addition of 16-Lead Lead Frame Chip Scale Package..Universal
Edits to Features.................................................................................1
Edits to General Description...........................................................1
Addition of LFCSP Pin Configuration...........................................4
Edit to Absolute Maximum Ratings................................................4
Addition to Ordering Guide............................................................4
Addition of CP-16 Outline Dimensions .....................................19
2/01—Changed from Rev. 0 to Rev A Edits to Notes in the Ordering Guide
SPECIFICATIONS VCC = 2.7 V to 3.6 V, VREF = 2.5 V internal or external, fDCLK = 2 MHz; TA = −40°C to +85°C, unless otherwise noted.
Table 1. Footnotes on next page.
Temperature range as follows: A, B Versions: –40°C to +85°C.
2 See the section. Terminology Difference between Temp0 and Temp1 measurement. No calibration necessary.
4 Temperature Drift is –2.1 mV/°C. Sample tested @ 25°C to ensure compliance.
6 See the Power vs. Throughput Rate section.
TIMING SPECIFICATIONS TA = TMIN to TMAX, unless otherwise noted; VCC = 2.7 V to 5.25 V, VREF = 2.5 V.
Table 2. Timing Specifications1 Sample tested at 25°C to ensure compliance. All input signals are specified with tr = tf = 5 ns (10% to 90% of VCC) and timed from a voltage level of 1.6 V.
2 Mark/Space ratio for the DCLK input is 40/60 to 60/40. Measured with the load circuit of and defined as the time required for the output to cross 0.4 V or 2.0 V. Figure 2
Figure 24 t12 is derived from the measured time taken by the data outputs to change 0.5 V when loaded with the circuit of . The measured number is then extrapolated
back to remove the effects of charging or discharging the 50 pF capacitor. This means that the time, t12, quoted in the timing characteristics is the true bus relinquish
time of the part and is independent of the bus loading.
02164-D-002
200µA
1.6V
200µA
IOL
IOHOUTPUTPINFigure 2. Load Circuit for Digital Output Timing Specifications
ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted.
Table 3. _______
1 Transient currents of up to 100 mA do not cause SCR latch-up.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the
human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS 02164-D-003
AD7873
TOP VIEW
PIN 1INDICATOR
+VCC
BAT
GNDY–X–
DOUTBUS
DIN
DCLKFigure 3. LFCSP Pin Configuration
02164-D-004
+VCC
GND
VBAT
AUXFigure 4.QSOP/TSSOP Pin Configuration
Table 4. Pin Function Descriptions TERMINOLOGY
Integral Nonlinearity This 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.
Differential Nonlinearity This is the difference between the measured and the ideal 1 LSB
change between any two adjacent codes in the ADC.
Offset Error This is the deviation of the first code transition (00 . . . 000) to
(00 . . . 001) from the ideal, that is, AGND + 1 LSB.
Gain Error This is the deviation of the last code transition (111 . . . 110) to
(111 . . . 111) from the ideal (that is, VREF – 1 LSB) after the offset
error is adjusted out.
Track-and-Hold Acquisition Time The track-and-hold amplifier enters the acquisition phase on
the fifth falling edge of DCLK after the START bit has been
detected. Three DCLK cycles are allowed for the track-and-hold
acquisition time. The input signal is fully acquired to the 12-bit
level within this time even with the maximum specified DCLK
frequency. See the Analog Input section for more details.
On-Resistance This is a measure of the ohmic resistance between the drain and
source of the switch drivers.
TYPICAL PERFORMANCE CHARACTERISTICS
CURRE
NT (02164-D-005
TEMPERATURE (°C) Figure 5. Supply Current vs. Temperature
CURRE
NT (210
23002164-D-006
+VCC (V)Figure 6. Supply Current vs. +VCC
DELTA FROM 25
°C (LSB)
0.2002164-D-007
TEMPERATURE (°C) Figure 7. Change in Gain vs. Temperature
CURRE
NT (nA)02164-D-008
TEMPERATURE (°C) Figure 8. Power-Down Supply Current vs. Temperature
+VCC (V)02164-D-009
LE R
E (
SPS)Figure 9. Maximum Sample Rate vs. +VCC
DELTA FROM 25
°C (LSB)02164-D-010
TEMPERATURE (°C) Figure 10. Change in Offset vs. Temperature
NCE
CURRE
NT (5525401085100115130
SAMPLE RATE (kHz)02164-D-011
Figure 11. Reference Current vs. Sample Rate
02164-D-012
+VCC (V) Figure 12. Switch On Resistance vs. +VCC
(X+, Y+: +VCC to Pin; X-, Y-: Pin to GND)
RROR (LS35557595115135155175195
SAMPLING RATE (kSPS)02164-D-013
Figure 13. Maximum Sampling Rate vs. RIN
NCE
CURRE
NT (
TEMPERATURE (°C)02164-D-014
Figure 14. Reference Current vs. Temperature
02164-D-015
TEMPERATURE (°C) Figure 15. Switch On Resistance vs. Temperature
(X+, Y+: +VCC to Pin; X-, Y-: Pin to GND)
INTE
RNAL V
(V
TEMPERATURE (°C)02164-D-016
–40–30–20–1001020304050607080Figure 16. Internal VREF vs. Temperature
(V
+VCC (V)02164-D-017
Figure 17. Internal VREF vs. +VCC
TEM
IOD
E VOLTA
GE (750
TEMPERATURE (°C)02164-D-018
Figure 18. Temp Diode Voltage vs. Temperature (2.7 V Supply)
TEM
1 D
IOD
E VOLTA
GE (02164-D-019
VSUPPLY (V)
2.73.33.03.6Figure 19. Temp 1 Diode Voltage vs. VSUPPLY (25°C)
INTE
RNAL V
(V02164-D-020
TURN-ON TIME (µS)20040060080010001200140016001800Figure 20. Internal VREF vs. Turn-on Time
TEM
0 D
IOD
E VOLTA
GE (
VSUPPLY (V)02164-D-021
Figure 21. Temp0 Diode Voltage vs. VSUPPLY (25°C)
NR (dB)
FREQUENCY (kHz)02164-D-022
Figure 22. Auxiliary Channel Dynamic Performance
RR (dB)102030405060708090100
VCC RIPPLE FREQUENCY (kHz)02164-D-023
Figure 23. AC PSRR vs. Supply Ripple Frequency
Figure 23 shows the power supply rejection ratio versus VDD
supply 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, f, to the power of a 100 mV sine wave
applied to the ADC VCC supply of frequency fS:
PSSR (dB) = 10 log (Pf/Pfs)
where:
Pf is power at frequency, f, in ADC output.
Pfs is power at frequency, fS, coupled onto the ADC VCC supply.
Here a 100 mV p-p sine wave is coupled onto the VCC supply.
Decoupling capacitors of 10 µF and 0.1 µF were used on the
supply.
CIRCUIT INFORMATION The AD7873 is a fast, low-power, 12-bit, single-supply A/D
converter. The AD7873 can be operated from a 2.2 V to 5.25 V
supply. When operated from either a 5 V supply or a 3 V supply,
the AD7873 is capable of throughput rates of 125 kSPS when
provided with a 2 MHz clock.
The AD7873 provides the user with an on-chip track-and-hold,
multiplexer, A/D converter, reference, temperature sensor, and
serial interface housed in a tiny 16-lead QSOP, TSSOP, or
LFCSP package, which offers the user considerable space-saving
advantages over alternative solutions. The serial clock input
(DCLK) accesses data from the part and also provides the clock
source for the successive approximation ADC. The analog input
range is 0 V to VREF (where the externally applied VREF can be
between 1 V and +VCC). The AD7873 has a 2.5 V reference on
board with this reference voltage available for use externally if
buffered.
The analog input to the ADC is provided via an on-chip
multiplexer. This analog input can be any one of the X, Y, and Z
panel coordinates, battery voltage, or chip temperature. The
multiplexer is configured with low-resistance switches that
allow an unselected ADC input channel to provide power and
an accompanying pin to provide ground for an external device.
For some measurements, the on-resistance of the switches could
present a source of error. However, with a differential input to
the converter and a differential reference architecture, this error
can be negated.
ADC TRANSFER FUNCTION The output coding of the AD7873 is straight binary. The
designed code transitions occur at successive integer LSB values
(that is, 1 LSB, 2 LSBs, and so on). The LSB size is VREF/4096.
The ideal transfer characteristic for the AD7873 is shown in
Figure 24.
02164-D-024
ADC CODE
ANALOG INPUT
1LSB0V+VREF–1LSB
000...000Figure 24. Transfer Characteristic
TYPICAL CONNECTION DIAGRAM Figure 25 shows a typical connection diagram for the AD7873
in a touch screen control application. The AD7873 features an
internal reference, but this can be overdriven with an external
low impedance source between 1 V and +VCC. The value of the
reference voltage sets the input range of the converter. The
conversion result is output MSB first, followed by the remaining
11 bits and three trailing zeroes, depending on the number of
clocks used per conversion. (See the Serial Interface section.)
For applications where power consumption is a concern, the
power management option should be used to improve power
performance. See Table 7 for available power management
options.
02164-D-025
2.2V TO 5V
SERIAL/CONVERSION CLOCK
CHIP SELECT
SERIAL DATA IN
CONVERTER STATUS
SERIAL DATA OUT
PEN INTERRUPT
50kΩ Figure 25. Typical Application Circuit
ANALOG INPUT Figure 26 shows an equivalent circuit of the analog input
structure of the AD7873, which contains a block diagram of the
input multiplexer, the differential input of the ADC, and the
differential reference.
Table 5 shows the multiplexer address corresponding to each
analog input, both for the SER/DFR bit in the control register
set high and low. The control bits are provided serially to the
device via the DIN pin. For more information on the control
register, see the Control Register section.
When the converter enters hold mode, the voltage difference
between the +IN and –IN inputs (see Figure 26) is captured on
the internal capacitor array. The input current on the analog
inputs depends on the conversion rate of the device. During the
sample period, the source must charge the internal sampling
capacitor (typically 37 pF). Once the capacitor is fully charged,
there is no further input current. The rate of charge transfer
from the analog source to the converter is a function of
conversion rate.
02164-D-026
Y+
REF
INT/
EXTY–GNDDATA OUT
VBAT
AUX
TEMPFigure 26. Equivalent Analog Input Circuit
Table 5. Analog Input, Reference, and Touch Screen Control 1 Internal node, not directly accessible by the user.
