Datasheet

DS_8010R_022 73S8010R Data Sheet
Rev. 1.6 17
3.3 Power Supply and Voltage Supervision
The Teridian 73S8010R smart card interface IC incorporates a LDO voltage regulator. The voltage
output is controlled by the digital input 5V/#V. This regulator is able to provide either 3 V or 5 V card
voltage from the power supply applied on the VPC pin.
Digital circuitry is powered by the power supply applied on the VDD pin. V
DD
also defines the voltage
range to interface with the system controller.
Three voltage supervisors constantly check the presence of the voltages V
DD
, V
PC
and V
CC
. A card
deactivation sequence is forced upon fault of any of these voltage supervisors. The two voltage
supervisors for V
PC
and V
CC
are linked so that a fault is generated to activate a deactivation sequence
when the voltage V
PC
becomes lower than V
CC
. This allows the 73S8010R to operate at lower V
PC
voltage when using 3 V cards only.
The voltage regulator can provide a current of at least 90 mA on V
CC
which easily complies with the
EMV 4.0 specification. The V
PC
voltage supervisor threshold values are defined from the EMV 4.0
standard. A third voltage supervisor monitors the V
DD
voltage. It is used to initialize the ISO-7816-3
sequencer at power-on, and to deactivate the card at power-off or upon a fault. The voltage threshold of
the V
DD
voltage supervisor is internally set by default to 2.3 V nominal. However, it may be desirable in
some applications to modify this threshold value. The pin VDDF_ADJ (pin 18 in the SO package, pin 17
in the QFN package) is used to connect an external resistor R
EXT
to ground to raise the V
DD
fault voltage
to another value V
DDF
. The resistor value is defined as follows:
R
EXT
= 56 kΩ / (V
DDF
- 2.33)
An alternative (more accurate) method of adjusting the V
DD
fault voltage is to use a resistive network of
R3 from the pin to supply and R1 from the pin to ground (see Figure 4). In order to set the new threshold
voltage, the equivalent resistance must be determined. This resistance value will be designated Kx. Kx
is defined as R1/(R1+R3). Kx is calculated as:
Kx = (2.789 / V
TH
) - 0.6125 where V
TH
is the desired new threshold voltage.
To determine the values of R1 and R3, use the following formulas.
R3 = 24000 / Kx R1 = R3*(Kx / (1 – Kx))
Taking the example above, where a V
DD
fault threshold voltage of 2.7 V is desired, solving for Kx gives:
 Kx = (2.789 / 2.7) - 0.6125 = 0.42046.
Solving for R3 gives:  R3 = 24000 / 0.42046 = 57080.
Solving for R1 gives:  R1 = 57080 *(0.42046 / (1 – 0.42046)) = 41412.
Using standard 1 % resistor values gives R3 = 57.6 KΩ and R1 = 42.4 KΩ.
These values give an equivalent resistance of Kx = 0.4228, a 0.6% error.
If the 2.3 V default threshold is used, this pin must be left unconnected.