TDA8029 Datasheet, PDF (43/58 Pages) NXP Semiconductors – Low power single card reader

Philips Semiconductors
Low power single card reader
Product specification
TDA8029
8.11 Supply
The circuit operates within a supply voltage range of
2.7 to 6 V. The supply pins are V_DD, DCIN, GND and
PGND. Pins DCIN and PGND supply the analog drivers to
the cards and have to be externally decoupled because of
the large current spikes the card and the step-up converter
can create. V_DD and GND supply the rest of the chip.
An integrated spike killer ensures the contacts to the card
to remain inactive during power-up or -down. An internal
voltage reference is generated which is used within the
step-up converter, the voltage supervisor, and the V_CC
generators.
V_DCIN may be higher than V_DD.
The voltage supervisor generates an alarm pulse, whose
length is defined by an external capacitor connected to the
CDEL pin, when V_DD is too low to ensure proper operation
(1 ms per 2 nF typical). This pulse is used as a Power-on
reset pulse, and also to block either any spurious signals
on card contacts during controllers reset or to force an
automatic deactivation of the contacts in the event of
supply drop-out (see Sections 8.16 and 8.17).
After power-on or after a voltage drop, the bit SUPL is set
within the Hardware Status Register (HSR) and remains
set until HSR is read when the alarm pulse is inactive.
As long as the Power-on reset is active, INT0_N is LOW.
The same occurs when leaving shut-down mode or when
the RESET pin has been set active.
handbook, full pagewidth_Vth1
VDD
Vth2
CDEL
RSTOUT
SUPL
INT
Power-on
tw
Status read
Supply dropout
Reset by CDEL
Fig.11 Voltage supervisor.
Power-off
MDB815
2003 Oct 30
43