AK4186 AKM [Asahi Kasei Microsystems], AK4186 Datasheet - Page 7

• Manufacturer Part Number: AK4186
• Description: Low Power Touch Screen Controller with I2C Interface
• Manufacturer: AKM [Asahi Kasei Microsystems]

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The AK4186 consists of the following blocks:
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The AK4186 integrates a 12bit successive approximation resistor (SAR) A/D converter for position measurement,
temperature, and auxiliary input. The architecture is based on capacitive redistribution algorithm, and an internal
capacitor array functions as the sample/hold (S/H) circuit.
The SAR A/D converter output is a straight binary format as shown below:
The f
depends on the input mode. Position and pen pressure are measured in differential mode, and then IN is measured in
single-ended mode. The AK4186 is controlled by 8bit serial command. A/D conversion result is 12bit data output on
the SDA pin.
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The analog input channel is automatically selected in sequential measurement mode. When position detection (X-axis
and Y-axis) and pen pressure are selected as analog inputs in differential mode, the full scale (ΔVREF) is the voltage
difference between the non-inverting terminal and the inverting terminal of the measured axis (e.g. X-axis
measurement: (XP) – (XN)). Analog input to A/D converters (ΔAIN) is the voltage difference between the non-
inverting terminal of the non-measured axis and the inverting terminal of the measured axis. At single-ended mode, the
full scale of A/D converter (ΔVREF) is the voltage difference between the VDD and the VSS. The analog input of A/D
converter (ΔAIN) is the voltage difference between the selected channel (IN) and the VSS.
If the source of analog input is high impedance, longer tracking time is required. Then A/D conversion should be started.
MS1068-E-04
Z1 Measure (Pressure)
Z2 Measure (Pressure)
Analog Inputs
Function Overview
A/D Converter for Touch Screen
Channel Selection
OSC
X-axis Measure
Y-axis Measure
AIN Measure
clock of an internal oscillator is used for A/D conversion. The full scale (ΔVREF) of the A/D converter
● 1.6V Successive Approximation Resister (SAR) A/D converter
● 4-wire or 5-wire resistive touch screen controller interface
● Single or Continuous A/D conversion
● Internal Clock for SAR A/D Converter
● I C
2
TM
I/F
X-Driver
Status of Driver Switch
XN-ON
XN-ON
OFF
OFF
ON
(ΔVREF-2.5LSB) ~ (ΔVREF-1.5LSB)
(ΔVREF-1.5LSB)~ ΔVREF
Table 2. Measurement Mode (4-wire)
Y-Driver
0.5LSB ~ 1.5LSB
YP-ON
YP-ON
OFF
OFF
Input Voltage
ON
OPERATION OVERVIEW
0 ~ 0.5LSB
ΔVREF: (VREF+) – (VREF-)
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Table 1. Output Code
ADC input (ΔAIN)
AIN+
YN
YP
XP
XP
IN
- 7 -
GND
AIN-
XN
YN
XN
XN
Output Code
Reference Voltage (ΔVREF)
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FFFH
FFEH
001H
000H
VREF+
VREF
XP
YP
YP
YP
VREF-
GND
XN
YN
XN
XN
Ref. Mode
[AK4186]
DFR
DFR
DFR
DFR
SER
2011/03