73S8023C-IM/F Maxim Integrated Products, 73S8023C-IM/F Datasheet - Page 9

• Manufacturer Part Number: 73S8023C-IM/F
• Description: IC SMART CARD INTERFACE 32-QFN
• Manufacturer: Maxim Integrated Products
• Type: Smart Card Interfacer

Specifications of 73S8023C-IM/F

• Controller Type: Smart Card Interface
• Interface: *
• Voltage - Supply: 2.7 V ~ 3.6 V
• Current - Supply: 4.9mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN Exposed Pad
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DS_8023C_019
5 Voltage Supervision
Two voltage supervisors constantly check the presence of the voltages V
sequence is triggered upon a fault detected by these voltage supervisors.
The digital circuitry is powered by the power supply applied on the VDD pin. V
range for the interface with the system controller. The V
ISO-7816-3 sequencer at power-on, and also to deactivate the card at power-off or upon a fault. The
voltage threshold of the V
may be desirable, in some applications, to modify this threshold value. The pin VDDF_ADJ (pin 17) is
used to connect an external resistor R
The resistor value is defined as follows:
An alternative (more accurate) method of adjusting the V
R3 from the pin to supply and R1 from the pin to ground (see
Schematic
This resistance value will be designated Kx. Kx is defined as R1/(R1+R3). Kx is calculated as:
To determine the values of R1 and R3, use the following formulas:
Taking the example above, where a V
Solving for R3 gives:
Solving for R1 gives:
Using standard 1 % resistor values gives R3 = 191 kΩ and R1 = 115 kΩ. These values give an
equivalent resistance of Kx = 0.376, a 0.3% error.
Using 1% external resistors and a parallel resistance of 72 k ohms will result in a +/- 6% tolerance in the
value of VDD Fault. The sources of variation due to integrated circuit process variations and mismatches
include the internal reference voltage (less than +/- 1%), the internal comparator hysteresis and offset
(less than +/- 1.7% for part-to-part, processing and environment), the internal resistor value mismatch and
value variations (less than 1.8%), and the external resistor values (1%).
If the 2.3 V default threshold is acceptable, this pin must be left unconnected.
Rev. 1.5
R
Kx = (2.649 / V
R3 = 72000 / Kx
 Kx = (2.649 / 2.7) - 0.6042 = 0.377
EXT
). In order to set the new threshold voltage, the equivalent resistance must be determined.
= 180 kΩ /(V
TH
 R3 = 72000 / 0.377 = 191 kΩ.
 R1 = 191000 *(0.377 / (1 – 0.377)) = 115.6 kΩ.
) - 0.6042 where V
DD
DDF
voltage supervisor is internally set by default to 2.3 V nominal. However, it
- 2.33)
R1 = R3*(Kx / (1 – Kx))
DD
EXT
fault threshold voltage of 2.7 V is desired, solving for Kx gives:
to ground to raise the V
TH
is the desired new threshold voltage.
DD
DD
Voltage supervisor is also used to initialize the
fault voltage is to use a resistive network of
Figure 11: 73S8023C – Typical Application
DD
fault voltage to another value, V
DD
and V
DD
also defines the voltage
CC
73S8023C Data Sheet
. A card deactivation
DDF
.
9