AD7889 Analog Devices, AD7889 Datasheet - Page 37

• Manufacturer Part Number: AD7889
• Description: Low Voltage Controller for Touch Screens
• Manufacturer: Analog Devices

Specifications of AD7889

• Resolution (bits): 12bit
• # Chan: 6
• Sample Rate: 105kSPS
• Interface: I²C/Ser 2-Wire,Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni Vdd
• Adc Architecture: SAR
• Pkg Type: CSP

For detailed information on grounding and layout considerations
for the AD7879/AD7889, refer to the AN-577 Application Note,
Layout and Grounding Recommendations for Touch Screen
Digitizers.
LEAD FRAME CHIP SCALE PACKAGES
The lands on the lead frame chip scale package (CP-16-10) are
rectangular. The printed circuit board (PCB) pad for these lands
should be 0.1 mm longer than the package land length and
0.05 mm wider than the package land width. Center the land on
the pad to maximize the solder joint size.
The bottom of the lead frame chip scale package has a central
thermal pad. The thermal pad on the PCB should be at least as
large as this exposed pad. To avoid shorting, provide a clearance
GROUNDING AND LAYOUT
SCREEN
TOUCH
NC = NO CONNECT
1
2
3
4
NC
NC
Y+
X–
Figure 46. Typical Application Circuit
AD7879/
AD7889
PENIRQ/INT/DAV
Rev. C | Page 37 of 40
0.1µF
DOUT
NC
NC
of at least 0.25 mm between the thermal pad and the inner
edges of the land pattern on the PCB. Thermal vias can be used
on the PCB thermal pad to improve the thermal performance of
the package. If vias are used, incorporate them into the thermal
pad at a 1.2 mm pitch grid. The via diameter should be between
0.3 mm and 0.33 mm, and the via barrel should be plated with
1 oz. of copper to plug the via.
Connect the PCB thermal pad to GND.
WLCSP ASSEMBLY CONSIDERATIONS
For detailed information on the WLCSP PCB assembly and
reliability, see the AN-617 Application Note, MicroCSP™ Wafer
Level Chip Scale Package.
12
11
10
9
0.1µF TO 10µF
(OPTIONAL)
CS
INT
SCLK
MISO
MOSI
REGULATOR
VOLTAGE
HOST
MAIN
BATTERY
AD7879/AD7889