NCN6010 Datasheet, PDF (9/16 Pages) ON Semiconductor – SIM Card Supply and Level Shifter

NCN6010
Figure 5. Power Down Sequence Oscillogram
Level Shifters
When the SIM card voltage is either higher or lower than
the MPU V_DD supply, the level shifters can be
reprogrammed to cope with the expected output voltage.
When the MPU and the SIM card operate under the same
supply voltage, the DC/DC converter is not activated
(SIM_VCC = V_DD –50 mV) and the signals go directly
through the level shifters.
V_DD
The bi–directional I/O line provides a way to
automatically adapt the voltage difference between the µCU
and the SIM card. In addition with the pull up resistor, an
active pull up circuit (Figure 6 Q1 and Q2) provides a fast
charge of the stray capacitance, yielding a rise time fully
within the ISO/EMV specifications.
V_CC
20 k
I/O
Q1
200 ns
Q2
200 ns
GND
20 k
SIM_IO
Q3
IO/CONTROL
LOGIC
GND
Figure 6. Basic I/O Line Interface
The typical waveform provided in Figure 7 shows how the
accelerator operates. During the first 200 ns (typical), the
slope of the rise time is solely a function of the pull up
resistor associated with the stray capacitance. During this
period, the PMOS devices are not activated since the input
voltage is below their Vgs threshold. When the input slope
crosses the Vgsth, the opposite one shot is activated,
providing a low impedance to charge the capacitance, thus
increasing the rise time as depicted in Figure 7. The same
mechanism applies for the opposite side of the line to make
sure the system is optimum.
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