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TDA8024AT View Datasheet(PDF) - Philips Electronics

Part Name
Description
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TDA8024AT
Philips
Philips Electronics Philips
TDA8024AT Datasheet PDF : 29 Pages
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Philips Semiconductors
IC card interface
Product specification
TDA8024
8 FUNCTIONAL DESCRIPTION
Throughout this document it is assumed that the reader is
familiar with ISO7816 terminology.
8.1 Power supply
The supply pins for the IC are VDD and GND. VDD should
be in the range of 2.7 to 6.5 V. All signals interfacing with
the system controller are referred to VDD, therefore VDD
should also supply the system controller. All card reader
contacts remain inactive during power-on or power-off.
The internal circuits are maintained in the reset state until
VDD reaches Vth2 + Vhys2 and for the duration of the
internal Power-on reset pulse, tW (see Fig.5). When VDD
falls below Vth2, an automatic deactivation of the contacts
is performed.
A DC/DC converter is incorporated to generate the
5 or 3 V card supply voltage (VCC). The DC/DC converter
should be supplied separately by VDDP and PGND. Due to
the possibility of large transient 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 m.
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:
VCC = 5 V and VDDP > 5.8 V; voltage follower
VCC = 5 V and VDDP < 5.7 V; voltage doubler
VCC = 3 V and VDDP > 4.1 V; voltage follower
VCC = 3 V and VDDP < 4.0 V; voltage doubler.
Supply voltages VDD and VDDP may be applied to the IC in
any sequence.
After powering the device, OFF remains LOW until
CMDVCC is set HIGH.
During power off, OFF falls LOW when VDD is below the
falling threshold voltage.
8.2 Voltage supervisor
8.2.1
WITHOUT EXTERNAL DIVIDER ON PIN PORADJ
(OR WITH TDA8024AT)
The voltage supervisor surveys the VDD supply. A defined
reset pulse of approximately 8 ms (tW) is used internally to
keep the IC inactive during power-on or power-off of the
VDD supply (see Fig.5).
As long as VDD is less than Vth2 + Vhys2, the IC remains
inactive whatever the levels on the command lines. This
state also lasts for the duration of tW after VDD has reached
a level higher than Vth2 + Vhys2.
When VDD falls below Vth2, a deactivation sequence of the
contacts is performed.
handbook, full pagewidth
VDD
ALARM
(internal signal)
tw
power-on
tw
supply dropout
2004 July 12
Fig.5 Voltage supervisor.
8
Vth2 + Vhys2
Vth2
power-off
MDB053
 

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