73S8010R
Low Cost Smart Card Interface
DATA SHEET
POWER SUPPLY AND VOLTAGE SUPERVISON
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 3V or 5V card voltage from the power
supply applied on the VPC pin.
Digital circuitry is powered by the power supply applied on the VDD pin. VDD also defines the voltage range to
interface with the system controller.
Three voltage supervisors constantly check the presence of the voltages VDD, VPC and VCC. A card deactivation
sequence is forced upon fault of any of these voltage supervisors. The two voltage supervisors for VPC and VCC
are linked so that a fault is generated to activate a deactivation sequence when the voltage VPC becomes lower
than VCC. It allows the 73S8010R to operate at lower VPC voltage when using 3V cards only.
The voltage regulator can provide a current of at least 90mA on VCC that comply easily with EMV 4.0 specification.
The VPC voltage supervisor threshold values are defined from EMV 4.0 standard. A third voltage supervisor
monitors the VDD voltage. It is used to initialize the ISO-7816-3 sequencer at power-on, and to deactivate the card
at power-off or upon fault. The voltage threshold of the VDD voltage supervisor is internally set by default to 2.3V
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 REXT to ground to
raise the VDD fault voltage to another value VDDF. The resistor value is defined as follows:
R
EXT= 56kΩ /(VDDF - 2.33)
An alternative method (more accurate) of adjusting the VDD fault voltage is to use a resistive network of R3 from
the pin to supply and R1 from the pin to ground (see applications diagram). 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 / VTH) - 0.6125 where VTH 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 VDD fault threshold voltage of 2.7V 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 = 57.6KΩ and R1 = 42.4KΩ.
These values give an equivalent resistance of Kx = 0.4228, a 0.6% error.
If the 2.3V default threshold is used, this pin must be left unconnected.
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© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 1.5
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
