mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 1234

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

T
F
Functional descriptions
NSCN: number of scan
I: constant current
C
ΔV: Hysteresis delta voltage
By this equation, an electrode with C = 20 pF, with a current source of I = 16 µA and ΔV
= 600 mV, PS = 2 and NSCN = 16 will have the following sampling time:
48.7.1.3 TSI reference oscillator
The TSI reference oscillator has the same topology of the TSI electrode oscillator. The
TSI reference oscillator instead of using an external capacitor for the electrode oscillator
has an internal reference capacitor which can be programmable. The SCANC[CAPTRM]
defines the internal reference capacitor trimming value *.
The TSI reference oscillator share the same voltage hysteresis levels defined with the
SCANC[DELVOL] and has an independent programmable current source controlled by
the SCANC[REFCHRG].
* The reference oscillator frequency is given by the following equation:
Where:
C
I
∆V : Hysteresis delta voltage
Considering C
1234
ref
cap_samp
ref_osc
elec
ref
: Reference oscillator current source
: Internal reference capacitor
: electrode capacitance
2 *1.0pF * 600mV
2*2*16*20pF*600mV
ref
Figure 48-69. Equation 4: TSI reference oscillator frequency
12µA
= 1.0 pF, I
16µA
MCF51JF128 Reference Manual, Rev. 2, 03/2011
ref
= 12 µA and ∆V = 600 mV, follows
F
ref_osc
10.0MHz
48µs
Preliminary
2 *C
I
ref
ref
* ΔV
Freescale Semiconductor, Inc.