PEB3265 Infineon Technologies Corporation, PEB3265 Datasheet - Page 126

• Manufacturer Part Number: PEB3265
• Description: (PEB326x / PEB426x) Dual Channel Slicofi-2 / Slic Duslic
• Manufacturer: Infineon Technologies Corporation

DuSLIC
Operational Description
Preliminary
4.8.2.11 Capacitance Measurements
Capacitance measurements with the DuSLIC are accomplished by using the integrated
ramp generator function. The ramp generator is capable of applying a voltage ramp to
the Ring- and Tip line with the flexibility of:
– Programmable slopes from 30 V/s to 2000 V/s
– Programmable start- and stop DC voltage offsets via ring offsets
– Programmable start time of the voltage ramp after enabling the levelmeter function
Figure 51
shows the voltage ramp and the voltage levels at the Ring and Tip line.
The slope of the ramp can be programmed (refer to CRAM coefficients). The ring offset
voltages RO1, RO2 and RO3 might be used as start and stop voltages. The ramp starts
for instance at RO1 and stops at RO2. The current can be calculated as
i(t) = C
*dU/dt, where dU/dt is the slope and i(t) is the current which will be
Measure
measured by the levelmeter. In order to measure accurate values, the integration has to
start after the current has settled to a constant value. This can be calculated by the time
constant of the ringer load. It is recommended to set the programmable ring generator
delay higher than 3 times the time constant of the ringer load. When there is a resistor
in parallel to the capacitor (e.g. leakage), it is recommended to measure symmetrically
around the voltage zero crossing. This can be achieved by programming the ring
generator delay appropriately (see DuSLICOS DC Control Parameter 2/3). The
integration time for the current measurement is determinded by the ring frequency (refer
to CRAM coefficients, see
Table
30). After the integration time the measurement
automatically stops only when the bit LM-ONCE in register LMCR1 is set. Otherwise the
levelmeter would continuously measure the current even if the ramp is finished and
turned into its constant voltage position, i.e., that because of the constant voltage no
current will flow.
Data Sheet
126
2000-07-14