Datasheet

TDA8023_1 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 01 — 16 July 2007 6 of 32
NXP Semiconductors
TDA8023
Low power IC card interface
8. Functional description
Remark: Throughout this document, it is assumed that the reader is familiar with
ISO 7816 and EMV 2000 terminology.
8.1 Power supplies
The supply pins for the TDA8023 are V
DD
and GND. V
DD
should be in the range from
2.7 V to 6.5 V. The supply voltages V
DD
, V
DD(INTF)
and V
DD(DCDC)
may be applied to the
TDA8023 in any time sequence.
All interface signals with the system controller are referenced to a separate supply voltage
V
DD(INTF)
on pin V
DDI
, that may be lower or higher than V
DD
.
For generating a supply voltage V
CC
of 5 V ± 5 % or 3 V ± 5 % used by the card, an
integrated DC-to-DC converter is incorporated. This DC-to-DC converter should be
separately supplied by V
DD(DCDC)
on pin V
DDP
and GNDP (from 2.7 V to 6.5 V).
The I
2
C-bus signals SDA and SCL may be externally referenced to a voltage higher than
V
DD
.
8.2 Voltage supervisor
8.2.1 Without external divider on pin PORADJ
The voltage supervisor surveys the V
DD
supply voltage. It is used as Power-On Reset
(POR) and as supply dropout detection during a card session. Supply dropout detection
ensures that a proper deactivation sequence is followed before the voltage is too low. A
reset pulse of duration t
W
(see Figure 4) is used internally for maintaining the TDA8023 in
the Inactive mode during powering up or powering down of V
DD
.
As long as V
DD
is less than V
th(POR)H
the TDA8023 will remain inactive whatever the levels
on the command lines are. This also lasts for the duration of t
W
after V
DD
has reached a
level higher than V
th(POR)H
. When V
DD
falls below V
th(POR)L
an automatic deactivation
sequence of the contacts is performed.
In this case (no external resistor bridge) it is mandatory to connect pin PORADJ to GND.
Fig 4. Voltage supervisor and Shutdown mode
001aag339
t
W
t
W
bus unresponsivebus unresponsive bus unresponsive
shutdown mode power offpower on
status read
V
hys(POR)
V
th(POR)H
V
th(POR)L
V
DD
INT
SDWN
status read