SX8655IWLTRT Semtech, SX8655IWLTRT Datasheet - Page 22

• Manufacturer Part Number: SX8655IWLTRT
• Description: 58T7566
• Manufacturer: Semtech

Specifications of SX8655IWLTRT

• Controller Type: Resistive Touch Screen
• Ic Interface Type: I2C, Serial
• Supply Voltage Range: 2.3V To 3.6V
• Operating Temperature Range: -40°C To +85°C
• Resolution (bits): 12bit

Nchan
ADVANCED COMMUNICATIONS & SENSING
In order to prevent this, one can estimate the maximum throughput achievable and set TOUCHRATE parameter
accordingly.
Tcom is the time between the end of conversion (ie NIRQ falling edge) and the end of channel data reading (i.e.
NIRQ rising edge). Maximum throughput implies that the host reacts “instantaneously” to NIRQ falling edge:
Tconv is the total conversion time:
- T
- N
- N
- POWDLY = 0.5us to 18.19ms, settling time as defined in RegTS0
- SETDLY = 0.5us to 18.19ms, settling time when filtering as defined in RegTS2
- Tosc is the period of the internal oscillator FOSCH
Some examples of maximum throughputs achievable with an I2C running at 400kHz are given below.
- CR = Coordinate Rate
- ECR = Equivalent Coordinate Rate = CR x N
- SR = Sampling Rate = CR x N
- ESR = Equivalent Sampling Rate = SR x N
For proper operation, the TOUCHRATE parameter should not exceed the theoretical maximum throughput CR.
Rev 1 – 25
2
2
2
4
I2C
filt
chan
= {1,3,5,7} based on the order defined for the filter FILT
is the period of the I2C clock SCL
= {1,2,3,4,5} based on the number of channels defined in RegChanMsk
NIRQ
I2C Read Channel
TOUCHRATE
Nfilt
1
3
5
3
th
tick
Idle
July 2011
Tconv us
POWDLY
35.5
35.5
[us]
0.5
2.2
Pen Detection
=
47 Tos c
SETDLY
Figure 25 – Incorrect (too high) TOUCHRATE setting
filt
[us]
0.5
0.5
0.5
0.5
Trate
Table 7 – Maximum Throughputs Examples
Tconv
MaxThroughput = 1 / (Tconv+Tcom)
+
N
c han
Tconv
170.6
152.8
315.0
T
Touch Conversion
51.7
[us]
c om
chan
P OWD LY
chan
Tcom
=
= CR x N
=
8
Not ready, tick ignored
Resistive Touchscreen Controller with Proximity Sensing
+
Tcom
16
[us]
100
100
100
200
22
+
filt
N
N
x N
cha n
f ilt
–
chan
1
151.7
270.6
252.8
Total
[us]
515
T
SX8654/SX8655/SX8656
I 2C
SETD LY
[kcps]
=> Actual rate = TOUCHRATE/n
CR
6.6
3.7
1.9
+
Trate < Tconv+Tcom < n.Trate
4
21N
filt
+
[kcps]
Haptics Enabled 4/5-Wire
ECR
13.2
1
7.4
7.6
8
Tos c
www.semtech.com
[ksps]
11.1
SR
6.6
5.7
20
[ksps]
ESR
13.2
22.2
22.8
40