AK4184 Datasheet, PDF (30/36 Pages) Asahi Kasei Microsystems – TSC with Keypad Scanner and GPIO Expander

[AK4184]
SYSTEM DESIGN
Figure 17 shows a system connection diagram for the AK4184. The evaluation board [AKD4184] is available, which
demonstrates the optimum layout and power supply arrangement.
LED Driver
GPIO
Keypad
6x5
Digital I/O Supply
1.6∼AVDD
0.1µ
+10µ
NC
C3
C5 BRCONT GP1 GP3 NC
C1
C4
C6 GP0 GP2 GP5
GP4
R4
C2
R3 R5 _{Top View}
GP7 GP6
XP
AVDD
VSS2 R2 VSS2
XN
YP
IOVDD R1 BUSY DIN CSN PEN YN
NC KEYIRQN DOUT SCLK RESETN ^IRQN
VSS1 NC
0.1µ
0.01µ*
0.01µ*
0.01µ*
0.01µ*
Analog Supply
+10µ _{2.5∼3.6V}
4-wire
Touch Screen
µP
Note:
- VSS1 and VSS2 of the AK4184 should be distributed separately from the ground of external controllers.
- Do not allow digital input pins (CSN, SCLK, DIN pins) to float.
-The DOUT pin is floating except when communicating with the host processor. A 100kΩ pull-down or pull-
up register should be connected.
Figure 17. Typical connection diagram
■ Attention to the PCB wiring
The AK4184 requires careful attention to power and grounding. VSS1, VSS2 should be connected to analog ground
system analog ground and digital ground should be connected together as close as possible to where the supplies are
brought onto the printed circuit board. Decoupling capacitors should be as close to the AK4184 as possible, with the
small value ceramic capacitor being the closest.
When an EMI source is close to the touch panel analog signal line, EMI noise reduces analog performance
characteristics. Noise canceling capacitors as close as possible to each pin (XP, XN, YP, YN pins) of the AK4184 to
avoid this noise. (Figure 17)
MS0603-E-00
30
2007/04