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PDF AD7877 Data sheet ( Hoja de datos )
| Número de pieza | AD7877 | |
| Descripción | Touch Screen Controller | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AD7877 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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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
Data Sheet
Parameter
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
Output Impedance
LOGIC INPUTS
Input High Voltage, VINH
Input Low Voltage, VINL
Input Current, IIN
Input Capacitance, CIN4
LOGIC OUTPUTS
Output High Voltage, VOH
Output Low Voltage, VOL
Floating-State Leakage Current
Floating-State Output Capacitance4
Output Coding
CONVERSION RATE
Conversion Time
Throughput Rate
POWER REQUIREMENTS
VCC (Specified Performance)
VDRIVE
ICC
Converting Mode
Static
Min Typ Max
8
±1
±1
0 − VCC/2
0 − VCC
−0.4, +0.5
12
50
75
21
15
100
0 1000
Open
0.7 VDRIVE
0.3
VDRIVE
±1
10
VDRIVE − 0.2
0.4
±10
10
8
125
2.7
1.65
240
650
900
150
3.6
VCC
380
900
Shutdown Mode
1
1 See the Terminology section.
2 Difference between Temp0 and Temp1 measurement. No calibration necessary.
3 Temperature drift is −2.1 mV/°C.
4 Sample tested @ 25°C to ensure compliance.
Unit
Bits
Bits
V
V
V/µs
µs
pF
kΩ
mA
µA
V
V
µA
pF
V
V
µA
pF
µs
kSPS
V
V
µA
µA
µA
µA
µA
Test Conditions/Comments
Guaranteed monotonic by design
DAC register Bit 2 = 0, Bit 0 = 0
DAC register Bit 2 = 0, Bit 0 = 1
0 to 3/4 scale, RLOAD = 10 kΩ, CLOAD = 50 pF
RLOAD = 10 kΩ
Power-down mode
DAC register, Bit 2 = 1; full-scale current is set by RRNG
Power-down mode
Typically 10 nA, VIN = 0 V or VCC
ISOURCE = 250 µA, VCC/VDRIVE = 2.7 V to 5.25 V
ISINK = 250 µA
Straight (natural) binary
CS high to DAV low
Functional from 2.2 V to 5.25 V
Digital inputs = 0 V or VCC
ADC on, internal reference off, VCC = 3.6 V
ADC on, internal reference on, VCC = 3.6 V
ADC on, internal reference on, DAC on
ADC on, but not converting, internal reference off,
VCC = 3.6 V
Rev. E | Page 4 of 45
5 Page 
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 3000 3500 4000
CODE
Figure 12. ADC DNL Plot
22
20
18
16
14
12
10
8
2.7
X– TO GND
Y+ TO VCC
Y– TO GND
X+ TO VCC
3.1 3.5 3.9 4.3 4.7 5.1
VCC (V)
5.5
Figure 13. Switch On Resistance vs. VCC
(X+, Y+: VCC to Pin; X−, Y−: Pin to GND)
22
20
X– TO GND
18
16
14 Y– TO GND
Y+ TO VCC
12
10
8
–40
X+ TO VCC
–20 0
20 40
TEMPERATURE (°C)
60
80
Figure 14. Switch On Resistance vs. Temperature
(X+, Y+: VCC to Pin; X−, Y−: Pin to GND)
Data Sheet
16
14
12
10
8
6
4
2
0
–50 –30 –10
10
30
50
70
90
TEMPERATURE (C)
Figure 15. External Reference Current vs. Temperature
2.520
2.515
2.510
2.505
2.500
2.495
2.490
2.485
2.480
2.475
–50 –30 –10
10
30
50
70
90
TEMPERATURE (C)
Figure 16. Internal VREF vs. Temperature
2.508
2.506
2.504
2.502
2.500
2.498
2.496
2.6 2.9 3.2 3.5 3.8 4.1 4.4 4.7 5.0
VCC (V)
Figure 17. Internal VREF vs. VCC
Rev. E | Page 10 of 45
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AD7877.PDF ] | |
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