TDA8005A Datasheet, PDF (10/36 Pages) NXP Semiconductors – Low-power 3 V/5 V smart card coupler

Philips Semiconductors
Low-power (3 V/5 V) smart card coupler
Preliminary specification
TDA8005A
handbook, full pagewidth
Vth(VDD) + Vhys(VthVDD)
Vth(VDD)
VDD
Vth(DELAY)
VDELAY
ALARM
MGL333
Fig.4 Supply supervisor.
Low impedance supply (pin LIS)
For some applications, it is mandatory that the contacts to
the card (V_CC, RST, CLK and I/O) are low impedance while
the card is inactive and also when the coupler is not
powered. An auxiliary supply voltage on pin LIS ensures
this condition where I_LIS ≤ 5 µA for V_LIS = 5 V. This low
impedance situation is disabled when V_CC starts rising
during activation, and re-enabled when the step-up
converter is stopped during deactivation. If this feature is
not required, the LIS pin must be tied to V_DDD.
Step-up converter
Except for the V_CC generator and the other cards contacts
buffers, the whole circuit is powered by V_DDD and V_DDA.
If the supply voltage is 3 or 5 V, then a higher voltage is
needed for the ISO contacts supply. When a card session
is requested by the controller, the sequencer first starts the
step-up converter, which is a switched capacitors type,
clocked by an internal oscillator at a frequency of
approximately 2.5 MHz. The output voltage V_step-up is
regulated at approximately 6.5 V and then fed to the V_CC
generator. V_CC and DGND are used as a reference for all
other cards contacts.
The step-up converter may be chosen as a doubler or a
tripler by mask option, depending on the voltage and the
current needed on the card.
ISO 7816 security
The correct sequence during activation and deactivation of
the card is ensured through a specific sequencer, clocked
by a division ratio of the internal oscillator.
Activation (START signal P05; see Table 3) is only
possible if the card is present (PRES HIGH or LOW
according to mask option), and if the supply voltage is
correct (ALARM signal inactive); CLK and RST are
controlled by RSTIN (internal signal; port P04), allowing
the correct count of CLK pulses during answer-to-reset
from the card.
The presence of the card is signalled to the controller by
the OFF signal (port P10; see Table 3).
During a session, the sequencer performs an automatic
emergency deactivation in the event of card take-off,
supply voltage drop, or hardware problems. The OFF
signal falls thereby warning the controller.
1998 Mar 20
10