sx8675iwltrt Semtech Corporation, sx8675iwltrt Datasheet - Page 39

• Manufacturer Part Number: sx8675iwltrt
• Description: Haptics Enabled Multitouch 4/5-wire Resistive Touchscreen Controller With Proximity Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
The carrier frequency of VMOUT_Freq is defined as following:
If AmplitudeCode is within HAPTSQUELCH range (for more than 512/VMOUT_Freq):
Else:
AmplitudeCode (signed) is defined differently depending on the mode selected (PWM or I2C), see below.
Please note that whatever setting, VMOUT is physically limited to [MVDD;-MVDD], ie saturation effect.
6.3.2
PWM mode is selected when HAPTMODE = 0.
In this mode, AmplitudeCode is extracted/updated at each MIN period from MIN_DutyCycle:
6.3.3
I2C mode is selected when HAPTMODE = 1.
In this mode, AmplitudeCode = HAPTAMP (signed, internally sampled at MIN_Freq). MIN is still used to extract
VMOUT carrier frequency.
6.4
The haptics interface integrates a short-circuit protection circuit which detects when MIDD is abnormally high i.e.
above ISHORT.
(MOUTN & MOUTP grounded). When the short-circuit is removed the haptics operations will resume normally.
Rev 1 – 25
Short-Circuit Protection
PWM Mode
MIN_DutyCycle ≈ 0% => AmplitudeCode = -127
…
MIN_DutyCycle = 49.6% => AmplitudeCode = -1
MIN_DutyCycle = 50% => AmplitudeCode = 0
MIN_DutyCycle = 50.4% => AmplitudeCode = +1
…
MIN_DutyCycle ≈ 100% => AmplitudeCode = +127
I2C Mode
th
July 2011
VMOUT_Freq(Hz) = (MIN_Freq / HAPTRANGE) / (HAPTTIMER +1)
Under a short-circuit event (HAPTSHORTSTAT=1) the haptics block will stop operation
VMOUT_Envelope(V) = (AmplitudeCode / 127) x 1.135 * HAPTGAIN
VMOUT_Freq(Hz) = (MIN_Freq / HAPTRANGE)
Figure 50 – LRA Drive Signal Example
VMOUT_Envelope = 0V
Resistive Touchscreen Controller with Proximity Sensing
OR
39
SX8674/SX8675/SX8676
Haptics Enabled Multitouch 4/5-Wire
(PWM mode)
(I2C mode)
www.semtech.com