Datasheet
TDA8034T_TDA8034AT All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
Product data sheet Rev. 3.1 — 13 December 2012 13 of 30
NXP Semiconductors
TDA8034T; TDA8034AT
Smart card interface
8.10 Automatic determining of card supply voltage
The supply voltage (V
CC
) that the card requires is determined automatically by monitoring
the duration of the HIGH state (logic 1) on pin CMDVCCN before the activation command
(CMDVCCN falling edge) occurs. If pin CMDVCCN stays HIGH for more than 30 ms,
activation occurs with V
CC
set to 5 V. If pin CMDVCCN stays HIGH for less than 15 ms,
activation occurs with V
CC
set to 3 V.
To activate the card at V
CC
= 5 V, pin CMDVCCN must stay HIGH for t0 > 30 ms before
going LOW (logic 0).
To activate the card at V
CC
= 3 V, pin CMDVCCN must stay HIGH for t0 < 15 ms before
going LOW (logic 0).
If pin CMDVCCN is HIGH for more than 15 ms (t0 > 15 ms) but less than 30 ms, pin
CMDVCCN must be set LOW for t1 (200 s<t1<700s), and then HIGH for t2
(200 s < t2 < 15 ms) before going LOW.
(1) Deactivation caused by card withdrawal.
(2) Deactivation caused by short-circuit.
Fig 9. Operation of debounce feature with pins OFFN, CMDVCCN, PRESN and V
CC
001aal411
PRESN
OFFN
t
deb
t
deb
CMDVCCN
V
CC
(1) (2)
Fig 10. Card activation, V
CC
= 5 V, t0 > 30 ms
Fig 11. Card activation, V
CC
= 3 V, t0 < 15 ms
001aak998
CMDVCCN
3 V or 5 V 5 V
t0
V
CC
001aak999
CMDVCCN
3 V or 5 V 3 V
t0
V
CC