TDA8029 Datasheet, PDF (41/59 Pages) NXP Semiconductors – Low power single card reader

Philips Semiconductors
TDA8029
Low power single card reader
8.11 Supply
The circuit operates within a supply voltage range of 2.7 V 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 Section 8.16
and Section 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.
V_th1
V_DD
V_th2
CDEL
t_w
RSTOUT
SUPL
INT
power-on
Fig 11. Voltage supervisor
status read
supply dropout
reset by CDEL
power-off
mdb815
8.12 DC-to-DC converter
Except for V_CC generator, and the other card contacts buffers, the whole circuit is powered
by V_DD and DCIN. If the supply voltage is 2.7 V, then a higher voltage is needed for the
ISO contacts supply. When a card session is requested by the controller, the sequencer
first starts the DC-to-DC converter, which is a switched capacitors type, clocked by an
internal oscillator at a frequency of approximately 2.5 MHz.
9397 750 14145
Product data sheet
Rev. 03 — 22 February 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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