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5.7.9.1 Touch-Screen Conversion Initiated at Touch Detect
(
)
(
)
(
)
coordinate
PRE
SNS
PVS
AVG
BITS
CONV
AVG
1
CLK
DEL
t
2
t
2
N
1
t
2
N
n
13
t
22
t
=
+
+
+
+
+
+
+
Programmed
forSelf-
Controlled
X-Y Scan
Mode
Reading
Y-Data
Register
Sample,Conversion
and Averagingfor
Y-Coordinate
Detecting
Touch
CONTROL INTERFACEDEACTIVATED
TouchIsDetected
PINTDAV
(As
andDATA_AVA
[Pg3/R3,D1–D0=10])
PENIRQ
PINTDAV
(As
[P3/R3,D1–D0=00])
PENIRQ
TouchIsDetected
PINTDAV
(As
[P3/R3,D1–D0=01])
DATA_AVA
Reading
X-Data
Register
Detecting
Touch
Sample,Conversion
and Averagingfor
X-Coordinate
Detecting
Touch
Sample,Conversion
and Averagingfor
Y-Coordinate
Detecting
Touch
TSC2117
Low-Power Audio Codec With Embedded miniDSP, Stereo Class-D
Speaker Amplifier, and Smart Four-Wire Touch-Screen Controller
SLAS550A – APRIL 2009 – REVISED JUNE 2009
www.ti.com
5.7.9.1.1 Self-Controlled X-Y Scan Mode
The time needed to get a converted X/Y coordinate for reading (not including the time needed to send the
command over the SPI bus) can be calculated by:
(1)
This formula is valid only if page 2/register 18, bits D6–D5 = 00, which means SAR data update is not kept on hold for reading
converted data.
(2)
After touch detect, the formula holds true from the second conversion onwards.
(3)
All the programmable delay tDEL, tPVS, tSNS and tPRE scale accordingly based on the actual divider setting and time period of the
clock used to generate this. See the respective control register settings to understand the scale factors.
(4)
If page 3/register 3, bits D1–D0 = 00, then in case of continuous touch, PINTDAV as shown in
Figure 5-48 remains high for
approximately tPRE. If page 3/register 3, bits D1–D0 = 10, then in case of continuous touch, PINTDAV remains high for approximately
(tPRE + tDEL).
where:
tCLK = tOSC or tMCLK × DIV3 (based on page 3/register 17, bit D7 setting)
tCONV = tCLK × DIV1
DIV1 = Divider setting configured in page 3/register 2, bits D4–D3
DIV3 = Divider setting configured in page 3/register 17, bits D6–D0
NBITS = SAR ADC resolution set in page 3/register 2, bits D6–D5
NAVG = Number of averages selected using page 3/register 2, bits D1–D0. For no averaging, NAVG = 1.
tOSC = Clock period of on-chip oscillator, typical value is 122 ns (i.e., 8.2 MHz)
tMCLK = Extenal MCLK clock period
n1 = 6 if DIV1 = 1; otherwise, n1 = 7
tDEL = Delay time setting as configured in page 3/register 15, bits D6–D4; it is 0 if page 3/register 15,
bit D7 = 0.
tPVS = Panel-voltage stabilization time as set in page 3/register 5, bits D2–D0
tSNS = Sense time as set in page 3/register 4, bits D2–D0
tPRE = Precharge time as set in page 3/register 4, bits D6–D4
Figure 5-48. TSC2117 Self-Controlled X-Y Scan Mode
82
APPLICATION INFORMATION