TDA8035HN Datasheet, PDF (15/32 Pages) NXP Semiconductors – Smart card interface externally by a resistor bridge

NXP Semiconductors
TDA8035HN
Smart card interface
8.10 Fault detection
The following fault conditions are monitored by the circuit:
1. Short-circuit or high current on V_CC
2. Card removal during transaction
3. V_DDP or V_DD(INTF) or Vreg dropping
4. Overheating.
There are two different cases (see Figure 10 on page 16):
1. CMDVCCN High: (outside a card session) then, OFFN 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_DDP is detected
by the supply supervisor, generates an internal power-on reset pulse, but does not act
upon OFFN. The card is not powered-up, so no short-circuit or overheating is
detected.
2. CMDVCCN Low: (within a card session) then, OFFN falls Low in any of the
aforementioned cases. As soon as the fault is detected, an emergency deactivation is
automatically performed. When the system controller sets CMDVCCN back to High, it
may sense OFFN again after complete deactivation sequence in order to distinguish
between a hardware problem or a card extraction (OFFN will then go back High if the
card is still present).
Depending on the type of card presence switch within the connector (normally close or
normally open), and on the mechanical characteristics of the switch, a bouncing may
occur on PRESN signal at card insertion or withdrawal. Consequently, a debounce feature
of approximately 4.05 ms (t_deb = 1280 × 1/(fosc(int)_Low) is integrated in the device.
Figure 11 on page 16 When the card is inserted, OFFN goes High only at the end of the
debouncing time.
When the card is extracted, an automatic deactivation sequence of the card is performed
on the first True/False transition on PRESN, and OFFN goes Low .
TDA8035HN
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1.0 — 19 April 2011
© NXP B.V. 2011. All rights reserved.
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