AD7877 Analog Devices, AD7877 Datasheet - Page 32

• Manufacturer Part Number: AD7877
• Description: Touch Screen Controller
• Manufacturer: Analog Devices

Specifications of AD7877

• Resolution (bits): 12bit
• # Chan: 9
• Sample Rate: 125kSPS
• Interface: Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP

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, refer to the AN-577 Application Note, Layout
and Grounding Recommendations for Touch Screen Digitizers.
PCB DESIGN GUIDELINES FOR CHIP SCALE
PACKAGES
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 0.05 mm wider than
the package land width. To ensure that the solder joint size is
maximized, center the land on the pad.
SECONDARY
BATTERY
BATTERY
MAIN
REGULATOR
VOLTAGE
MEASUREMENT
TEMPERATURE
DIODE
REMOTE CONTROL
HOTSYNC INPUTS
FROM AUDIO
V
1.0µF–10µF
(OPTIONAL)
IN
CONVERTER
FROM
Figure 48. Typical Application Circuit
DC-DC
0.1µF
0.1µF
OUT
Rev. D | Page 32 of 44
FB
1
2
3
4
5
6
7
8
SCREEN
TOUCH
NC
BAT2
BAT1
AUX3/GPIO3
AUX2/GPIO2
AUX1/GPIO1
V
NC
CC
32
9
31
10
The bottom of the chip scale package has a central thermal pad.
The thermal pad on the printed circuit board should be at least
as large as this exposed pad. On the printed circuit board, provide a
clearance of at least 0.25 mm between the thermal pad and the
inner edges of the pad pattern to ensure that shorting is avoided.
Using thermal vias on the printed circuit board thermal pad
improves the thermal performance of the package. If vias are
used, incorporate them in the thermal pad at a 1.2 mm pitch
grid. Keep the via diameter between 0.3 mm and 0.33 mm. The
via barrel should be plated with 1 oz. copper to plug the via.
The user should connect the printed circuit board thermal pad
to AGND.
11
30
AD7877
29
12
R
V
RNG
28
13
CC
14
27
TO LCD
BACKLIGHT
15
26
STOPACQ
NC = NO CONNECT
PENIRQ
ALERT
25
16
GPIO4
DAV
DIN
NC
CS
HSYNC SIGNAL
24
23
22
21
20
19
18
17
FROM LCD
GPIO
INT1
INT2
SCLK
MISO
MOSI
CS
PENIRQ
HOST
Data Sheet