TDA8004AT Datasheet, PDF (10/22 Pages) NXP Semiconductors – IC card interface

Philips Semiconductors
IC card interface
Product specification
TDA8004AT
OSC_INT/64
CMDVCC
VUP
VCC
I/O
CLK
RST
tde
t10
t14
t13
high - Z
t12
t11
t15
FCE663
Fig.6 Deactivation sequence.
Fault detection
The following fault conditions are monitored by the circuit:
• Short-circuit or high current on V_CC
• Removing card during transaction
• V_DD dropping
• Overheating.
There are two different cases (see Fig.7)
1. CMDVCC HIGH: (outside a card session) then, OFF is
LOW if the card is not in the reader, and HIGH if the
card is in the reader. A supply voltage drop on V_DD is
detected by the supply supervisor which generates an
internal power-on reset pulse, but does not act upon
OFF. The card is not powered-up, so no short-circuit or
overheating is detected.
2. CMDVCC LOW: (within a card session) then, OFF falls
LOW if the card is extracted, or if a short-circuit has
occurred on V_CC, or if the temperature on the IC has
become too high. As soon as the fault is detected, an
emergency deactivation is automatically performed
(see Fig.8).
When the system controller sets CMDVCC back to
HIGH, it may sense OFF again in order to distinguish
between a hardware problem or a card extraction. If a
supply voltage drop on V_DD is detected whilst the card
is activated, then an emergency deactivation will be
performed, but OFF remains HIGH.
Depending on the type of card presence switch within the
connector (normally closed or normally open), and on the
mechanical characteristics of the switch, a bouncing may
occur on presence signals at card insertion or withdrawal.
There is no debounce feature in the device, so the
software has to take it into account; however, the detection
of card take off during active phase, which initiates an
automatic deactivation sequence is done on the first True/
False transition on PRES or PRES, and is memorized until
the system controller sets CMDVCC HIGH.
So, the software may take some time waiting for presence
switches to be stabilized without causing any delay on the
necessary fast and normalized deactivation sequence.
2004 May 10
10