Information

Delta Voltage
(DELVOL)
Electrode
charge current
(EXTCHRG)
Figure 49-64. TSI electrode oscillator circuit
The current source applied to the pad capacitance is 5-bit binary controlled by the
SCANC[EXTCHRG]. The hysteresis delta voltage is also configurable and is 3-bit binary
controlled by the SCANC[DELVOL]. The figure below shows the voltage amplitude
waveform of the electrode capacitance charging and discharging with a programmable
current.
Electrode
Voltage
Time
Electrode Capacitor Charging and
Discharging with constant current
Hysteresis
Voltage Delta
Figure 49-65. TSI electrode oscillator chart
The oscillator frequency is given by the following equation:
F
elec
I
2 * C
elec
*
ΔV
Figure 49-66. Equation 1: TSI electrode oscillator frequency
Where:
I: constant current
C
elec
: electrode capacitance
ΔV: Hysteresis delta voltage
Functional descriptions
K10 Sub-Family Reference Manual, Rev. 6, Nov 2011
1552 Freescale Semiconductor, Inc.