ST8024 STMicroelectronics, ST8024 Datasheet - Page 10

• Manufacturer Part Number: ST8024
• Description: SMARTCARD INTERFACE
• Manufacturer: STMicroelectronics

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ST8024
Figure 3: Definition of output and input transition times
FUNCTIONAL DESCRIPTION
Throughout this document it is assumed that the reader is familiar with ISO7816 terminology.
POWER SUPPLY
The supply pins for the IC are V
interfacing with the system controller are referred to V
controller. All card reader contacts remain inactive during power-on or power-off.
The internal circuits are maintained in the reset state until V
the internal Power-on reset pulse, t
the contacts is performed.
A DC/DC converter is incorporated to generate the 5 or 3 V card supply voltage (V
converter should be supplied separately by V
currents, the two 100 nF capacitors of the DC/DC converter should be located as near as possible to the
IC and have an ESR less than 100 mΩ.
The DC/DC converter functions as a voltage doubler or a voltage follower according to the respective
values of VCC and VDDP (both have thresholds with a hysteresis of 100 mV).
The DC/DC converter function changes as follows:
Supply voltages V
After powering the device, OFF remains LOW until CMDVCC is set HIGH.
During power off, OFF falls LOW when V
VOLTAGE SUPERVISOR
- WITHOUT EXTERNAL DIVIDER ON PIN PORADJ
The voltage supervisor surveys the V
internally to keep the IC inactive during power-on or power-off of the V
As long as V
lines. This state also lasts for the duration of t
When V
10/23
V
V
V
V
CC
CC
CC
CC
= 5 V and V
= 5 V and V
= 3 V and V
= 3 V and V
DD
falls below V
DD
is less than V
DDP
DDP
DDP
DDP
DD
and V
> 5.8 V; voltage follower
< 5.7 V; voltage doubler
> 4.1 V; voltage follower
< 4.0 V; voltage doubler.
th2
, a deactivation sequence of the contacts is performed.
DDP
th2
may be applied to the IC in any sequence.
DD
+ V
W
and GND. V
(see Fig.4). When V
DD
hys2
supply. A defined reset pulse of approximately 8ms (t
DD
, the IC remains inactive whatever the levels on the command
is below the falling threshold voltage.
W
DDP
after V
DD
and PGND. Due to the possibility of large transient
should be in the range of 2.7 to 6.5 V. All signals
DD
DD
DD
, therefore V
DD
has reached a level higher than V
falls below V
reaches V
DD
DD
th2
th2
supply (see Fig.4).
should also supply the system
+V
, an automatic deactivation of
hys2
and for the duration of
CC
). The DC/DC
th2
W
) is used
+ V
hys2
.