73S8023C Data Sheet
DS_8023C_019
3 Oscillator
The 73S8023C device has an on-chip oscillator that can generate the smart card clock using an external
crystal (connected between the pins XTALIN and XTALOUT) to set the oscillator frequency. When the
card clock signal is available from another source, it can be connected to the pin XTALIN, and the pin
XTALOUT should be left unconnected. Signal CLKOUT is the buffered version of the signal on XTALIN.
4 DC-DC Converter – Card Power Supply
An internal DC-DC converter provides the card power supply. This converter is able to provide either 3 V
or 5 V card voltage from the power supply applied on the VDD pin. The digital ISO-7816-3 sequencer
controls the converter. Card voltage selection is carried out by the digital input 5V/#V.
The circuit is an inductive step-up converter/regulator. The external components required are 2 filter
capacitors on the power-supply input VDD (next to the LIN pin, 100 nF + 10 µF), an inductor, and an
output filter capacitor on the card power supply VCC. The circuit performs regulation by activating the
step-up operation when VCC is below a set point of 5.0 or 3.0 volts minus a comparator hysteresis voltage
and the input supply VDD is less than the set point for VCC. When VDD is greater than the set point for VCC
(VDD = 3.6 V, VCC =3 V) the circuit operates as a linear regulator.
Depending on the inductor values, the voltage converter can provide current on VCC as high as 100 mA.
The circuit provides over-current protection and limits ICC to 150 mA. When an over-current condition is
sensed, the circuit initiates a deactivation sequence from the control logic and reports back to the host
controller a fault on the interrupt output OFF.
Choice of the inductor
The nominal inductor value is 10 µH, rated for 400 mA. The inductor is connected between LIN (pin 2)
and the VDD supply voltage. The inductor value can be optimized to meet a particular configuration
(ICC_MAX). The inductor should be located on the PCB as close as possible to the LIN pin of the IC.
Choice of the VCC capacitor
Depending on the applications, the requirements in terms of both the VCC minimum voltage and the
transient currents that the interface must provide to the card are different. Table 1 shows the
recommended capacitors for each VCC power supply configuration and applicable specification.
Table 1: Choice of VCC Pin Capacitor
Specification Requirement
Min VCC Voltage
Application
Max Transient
Capacitor
Capacitor
Value
Specification
Allowed During
Current Charge
Type
Transient Current
EMV 4.1
ISO-7816-3
NDS
4.6 V
4.5 V
30 nAs
20 nAs
40 nAs
3.3 µF
1 µF
X5R/X7R w/
ESR < 100 mΩ
4.65 V
3.3 µF
8
Rev. 1.5
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
