Datasheet

TSC2101
SLAS392D− JUNE 2003 − REVISED MAY 2005
www.ti.com
75
CONVERSION TIME CALCULATIONS FOR THE TSC2101
Touch Screen Conversion Initiated at Touch Detect
The time needed to get a converted X/Y coordinate for reading can be calculated by (not including the time
needed to send the command over the SPI bus):
t
coordinate
+ 2
ȧ
ȱ
Ȳ
ǒ
t
PRE
) t
SNS
) t
PVS
Ǔ
125 ns
ȧ
ȳ
ȴ
t
OSC
) 2 NJN
AVG
ƪ
ǒ
N
BITS
) 1
Ǔ
8MHz
ƒ
conv
) n
1
) 12
ƫ
) 1Nj
t
OSC
) 18 t
OSC
) n
2
t
OSC
) n
3
t
OSC
where:
t
coordinate
= time to convert X/Y coordinate
t
PVS
= Panel voltage stabilization time
t
PRE
= precharge time
t
SNS
= sense time
N
AVG
= number of averages; for no averaging, N
AVG
= 1
N
BITS
= number of bits of resolution
ƒ
conv
= A/D converter clock frequency
t
OSC
= Oscillator clock period
n
1
= 6 ; if ƒ
conv
= 8 MHz
7 ; if ƒ
conv
≠ 8 MHz
n
2
= 4 ; if t
PVS
= 0 µs
0 ; if t
PVS ≠
0 µs
n
3
= 0 ; if t
SNS
= 32 µs
2 ; if t
SNS ≠
32 µs
t
PGDEL
= Programmable delay in between conversion for touch screen measurement
= 0: if programmable delay mode is disabled for touch screen measurement
(1)
t
PGDEL
delay is generated by using: Internal oscillator clock whose typical frequency is 1 MHz, in internal clock
mode, or MCLK/CLKDIV (as programmed in control register 14H/pag1) in external clock mode.
(2)
The above formula is valid exactly only when the codec is powered down. Also after touch detect the formula holds
true from second conversion onwards.
(3)
If D15−D14 of control register 01H/page 1 = 00, then in case of continuous touch PINTDAV remains high for
ǒ
t
PRE
) t
SNS
Ǔ
t
OSC
ń125 ns
. If D15−D14 of control register 01H/page 1 = 10/11, then in case of continuous touch
PINTDAC remains high for
ǒ
t
PRE
) t
SNS
Ǔ
t
OSC
ń125 ns ) t
PGDEL
.
Programmed
for Self
Controlled
X−Y Scan
Mode
Detecting Touch
Sample,Conversion &
Averaging for
Y−Coordinate
Reading
X−Data
Register
Reading
Y−Data
Register
Detecting
Touch
Sample,Conversion &
Averaging for
X−Coordinate
Detecting
Touch
Sample,Conversion &
Averaging for
Y−Coordinate
Detecting
Touch
SS DEACTIVATED
Touch Is Detected
(As PENIRQ
[D15−D14 = 00])
PINTDAV
(As PENIRQ & DATA_AVA
[D15−D14 = 10/11])
PINTDAV
Touch Is Detected
Touch Is Detected
(As DATA_AVA
[D15−D14 = 01])
PINTDAV