NCN8024R
CMDVCC
CRD_RST
CRD_CLK
CRD_IO
CRD_VCC
t
deact
Figure 6. Deactivation Sequence
FAULT DETECTION
• Card pin current limitation: in the case of a short circuit
to ground. No feedback is provided to the external MPU.
• LDO operation: the internal circuit continuously senses
In order to protect both the interface and the external smart
card, the NCN8024R provides security features to prevent
failures or damages as depicted here after.
the CRD_V voltage (in the case of either over or
CC
• Card extraction detection
under voltage situation).
• V under voltage detection
DD
• LDO operation: under−voltage detection on V
overload on VUP
or
DDP
• Short−circuit or overload on CRD_V
CC
• Overheating
• Card pin current limitation: in the case of a short circuit
to ground. No feedback is provided to the external
MPU
CRD_PRES
INT
CMDVCC
Debounce
Debounce
CRD_VCC
Powerdown Resulting of
Card Extraction
Powerdown Caused by
Short−Circuit
Figure 7. Fault Detection and Interrupt Management
Interrupt Pin Management:
A card session is opened by toggling CMDVCC High to
Low.
Before a card session, CMDVCC is supposed to be in a
High position. INT is Low if no card is present in the card
connector (Normally open or normally closed type). INT is
High if a card is present. If a card is inserted (INT = High)
During a card session, CMDVCC is Low and INT pin
goes Low when a fault is detected. In that case a deactivation
is immediately and automatically performed (see Figure 6).
When the microcontroller resets CMDVCC to High it can
sense the INT level again after having got completed the
deactivation.
As illustrated by Figure 7 the device has a debounce timer
of 8 ms typical duration. When a card is inserted, output INT
goes High only at the end of the debounce time. When the
card is removed a deactivation sequence is automatically
and immediately performed and INT goes Low.
and if V drops below the UVLO threshold then INT pin
DD
drops Low immediately. It turns back High when V
increases again over the UVLO limit (including hysteresis),
a card being still present.
DD
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