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AD7877 の電気的特性と機能
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AD7877のメーカーはAnalog Devicesです、この部品の機能は「Touch Screen Controller」です。 |
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製品の詳細 ( Datasheet PDF )
| 部品番号 AD7877 |
| 部品説明 Touch Screen Controller |
| メーカ Analog Devices |
ロゴ |
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Data Sheet
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 optional GPIOs
2 direct battery measurement channels (0.5 V to 5 V)
3 interrupt outputs
Touch-pressure measurement
Wake up on touch function
Specified throughput rate of 125 kSPS
Single supply, VCC of 2.7 V to 5.25 V
Separate VDRIVE level for serial interface
Shutdown mode: 1 µA maximum
32-lead, LFCSP, 5 mm × 5 mm package
25-ball,WLCSP, 2.5 mm × 2.8 mm package
Qualified for automotive applications
APPLICATIONS
Personal digital assistants
Smart hand-held devices
Touch screen monitors
Point-of-sale terminals
Medical devices
Cell phones
Pagers
GENERAL DESCRIPTION
The AD7877 is a 12-bit, successive approximation ADC with a
synchronous serial interface and low on resistance switches for
driving touch screens. The AD7877 operates from a single 2.7 V
to 5.25 V power supply (functional operation to 2.2 V), and
features throughput rates of 125 kSPS. The AD7877 features
direct battery measurement on two inputs, temperature and
touch-pressure measurement.
The AD7877 also has an on-board reference of 2.5 V. When not
in use, it can be shut down to conserve power. An external
reference can also be applied and varied from 1 V to +VCC, with
an analog input range of 0 V to VREF. The device includes a
shutdown mode that reduces its current consumption to less
than 1 µA.
Rev. E
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
Touch Screen Controller
AD7877
FUNCTIONAL BLOCK DIAGRAM
VCC
7
X+ 12
X– 10
Y+ 13
Y– 11
AUX1/GPIO1 6
AUX2/GPIO2 5
AUX3/GPIO3 4
BAT1 3
AD7877
BATTERY
MONITOR
X– Y– GND X+ Y+ VREF
DUAL 3-1
MUX
REF– REF+
9 TO 1 IN
12-BIT SUCCESSIVE
CLOCK
INPUT
APPROXIMATION ADC
MUX
WITH TRACK-AND-HOLD
BAT2 2
BATTERY
MONITOR
SEQUENCER
RESULTS
REGISTERS
STOP
ACQ
LOGIC
LIMIT
COMPARATOR
20 STOPACQ
14 AGND
TEMPERATURE
SENSOR
VREF 31
2.5V
REF
BUF
LIMIT
REGISTERS
ALERT STATUS/
MASK REGISTER
GPIO
REGISTERS
ALERT
LOGIC
AOUT 30
ARNG 29
8-BIT
DAC
DAC
REGISTER
CONTROL
REGISTERS
TO
GPIO1-3
CONTROL LOGIC AND SERIAL PORT
PEN INTERRUPT
AND WAKE-UP
ON TOUCH
15 DGND
22 ALERT
21 GPIO4
17 PENIRQ
18 19 23
26
27
28
CS DIN DAV DCLK DOUT VDRIVE
Figure 1.
To reduce the effects of noise from LCDs, the acquisition phase
of the on-board ADC is controlled via the STOPACQ pin. User-
programmable conversion controls include variable acquisition
time and first conversion delay. Up to 16 averages can be taken
per conversion. There is also an on-board DAC for LCD back-
light or contrast control. The AD7877 runs in either slave or
master mode using a conversion sequencer and timer. It is ideal
for battery-powered systems such as personal digital assistants
with resistive touch screens and other portable equipment.
The part is available in a 32-lead lead frame chip scale package
(LFCSP), and a 25-ball wafer level chip scale package (WLCSP).
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2004–2014 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 Page
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 Caution.................................................................................. 6
Pin Configurations and Function Descriptions ........................... 7
Typical Performance Characteristics ............................................. 9
Terminology .................................................................................... 13
Circuit Information ........................................................................ 14
Touch Screen Principles ............................................................ 14
Measuring Touch Screen Inputs ............................................... 15
Touch-Pressure Measurement .................................................. 16
STOPACQ Pin ............................................................................ 16
Temperature Measurement ....................................................... 17
Battery Measurement................................................................. 18
Auxiliary Inputs .......................................................................... 19
Limit Comparison ...................................................................... 19
REVISION HISTORY
12/14—Rev. D to Rev. E
Added Figure 50; Renumbered Sequentially .............................. 44
Updated Outline Dimensions ....................................................... 44
Changes to Ordering Guide .......................................................... 45
12/11—Rev. C to Rev. D
Change to Features Section ............................................................. 1
Updated Outline Dimensions ....................................................... 44
Changes to Ordering Guide .......................................................... 44
Added Automotive Products Section........................................... 44
9/09—Rev. B to Rev. C
Changes to Offset Error and Gain Error Parameters .................. 3
Added VBAT to GND Parameter ...................................................... 6
Changes to Pin 23 Description ....................................................... 7
Changes to Power Management (Control Register 2,
Bits[7:6]) Section ............................................................................ 22
Changes to Bit 7 Description (Table 17)...................................... 36
Updated Outline Dimensions ....................................................... 44
Changes Ordering Guide............................................................... 44
Data Sheet
Control Registers ............................................................................ 20
Control Register 1 ...................................................................... 20
Control Register 2 ...................................................................... 21
Sequencer Registers ................................................................... 22
Interrupts..................................................................................... 24
Synchronizing the AD7877 to the Host CPU......................... 25
8-Bit DAC ........................................................................................ 26
Serial Interface ................................................................................ 28
Writing Data ............................................................................... 28
Write Timing............................................................................... 29
Reading Data............................................................................... 29
VDRIVE Pin..................................................................................... 29
General-Purpose I/O Pins............................................................. 30
GPIO Configuration .................................................................. 30
Grounding and Layout .................................................................. 32
PCB Design Guidelines for Chip Scale Packages................... 32
Register Maps.................................................................................. 33
Detailed Register Descriptions ..................................................... 35
GPIO Registers ........................................................................... 42
Outline Dimensions ....................................................................... 44
Ordering Guide .......................................................................... 45
Automotive Products ................................................................. 45
6/06—Rev. A to Rev. B
Added Wafer Level Chip Scale Package ..........................Universal
Changes to Table 3.............................................................................6
Changes to Figure 21...................................................................... 11
Change to Figure 25 ....................................................................... 12
Changes to Figure 38 and Figure 39 ............................................ 23
Change to Figure 40 ....................................................................... 24
Changes to Data Available Output (DAV) Section .................... 24
Updated Outline Dimensions....................................................... 42
Changes to Ordering Guide .......................................................... 42
11/04—Rev. 0 to Rev. A
Changes to Absolute Maximum Ratings .......................................6
Changes to Figure 4...........................................................................7
Changes to Table 4.............................................................................7
Changes to Grounding and Layout section ................................ 32
Changes to Figure 42...................................................................... 32
Changes to Ordering Guide .......................................................... 43
7/04—Revision 0: Initial Version
Rev. E | Page 2 of 45
3Pages
Data Sheet
AD7877
TIMING SPECIFICATIONS
TA = TMIN to TMAX, unless otherwise noted, VCC = 2.7 V to 5.25 V, VREF = 2.5 V. 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.
Table 2.
Parameter
fDCLK 1
t1
t2
t3
t4
t5
t6 2
t72
t8 3
t9
Limit at TMIN, TMAX
10
20
16
20
20
12
12
16
16
16
0
Unit
kHz min
MHz max
ns min
ns min
ns min
ns min
ns min
ns max
ns max
ns max
ns min
Description
CS falling edge to first DCLK rising edge
DCLK high pulse width
DCLK low pulse width
DIN setup time
DIN hold time
CS falling edge to DOUT, three-state disabled
DCLK falling edge to DOUT valid
CS rising edge to DOUT high impedance
CS rising edge to DCLK ignored
1 Mark/space ratio for the DCLK input is 40/60 to 60/40.
2 Measured with the load circuit of Figure 3 and defined as the time required for the output to cross 0.4 V or 2.0 V.
3 t8 is derived from the measured time taken by the data outputs to change 0.5 V when loaded with the circuit shown in Figure 3. The measured number is then
extrapolated back to remove the effects of charging or discharging the 50 pF capacitor. This means that the time, t8, quoted in the timing characteristics is the true bus
relinquish time of the part and is independent of the bus loading.
TIMING DIAGRAMS
CS
DCLK
DIN
DOUT
t1
1
MSB
t2
2
t4
t3
3
t5
t9
15 16
LSB
t6
MSB
t7
t8
LSB
Figure 2. Detailed Timing Diagram
200µA
IOL
TO OUTPUT
PIN CL
50pF
1.6V
200µA
IOH
Figure 3. Load Circuit for Digital Output Timing Specifications
Rev. E | Page 5 of 45
6 Page
合計 : 30 ページ |
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