sx8654 Semtech Corporation, sx8654 Datasheet - Page 37

• Manufacturer Part Number: sx8654
• Description: Haptics Enabled 4/5-wire Resistive Touchscreen Controller With Proximity Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
If AmplitudeCode is within HAPTSQUELCH range (for more than 512/MIN_Freq in PWM mode, for more than
512/FOSCL in I2C mode):
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], i.e. saturation effect.
6.2.2
PWM mode is selected when HAPTMODE = 0.
In this mode, AmplitudeCode is extracted/updated at each MIN period from MIN_DutyCycle:
6.2.3
I2C mode is selected when HAPTMODE = 1.
In this mode, AmplitudeCode = HAPTAMP (signed, internally sampled at FOSCL). MIN is not used and should
be grounded. HAPTRANGE must be set to 1.
6.3
6.3.1
An LRA is a spring and mass with an electro-magnetic coil to move the mass. It is operated by applying an AC
signal at its resonant frequency (typ. ~175 Hz). Like pushing a swing at its resonance, it doesn’t need much
energy to keep it going, so drive current requirements are much lower than for ERMs. LRAs have moderately
high Q factors so that the drive frequency must match the resonant frequency within a few Hz to get optimum
amplitude.
LRA load is selected when HAPTTYPEEN = 01.
Rev 1 – 25
LRA Load
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
Introduction
th
July 2011
VMOUT(V) = (AmplitudeCode / 127) x 1.135 * HAPTGAIN
Figure 48 – ERM Drive Signal Example
VMOUT = 0V
Resistive Touchscreen Controller with Proximity Sensing
37
SX8654/SX8655/SX8656
Haptics Enabled 4/5-Wire
www.semtech.com