TDA8031 Datasheet, PDF (29/57 Pages) NXP Semiconductors – USB smart card reader (OTP or ROM)

Philips Semiconductors
USB smart card reader (OTP or ROM)
Product specification
TDA8030; TDA8031
8.2 SUPPLY
The supply to the chip is delivered by the USB-bus (pins
V_DDU and UGND).
8.2.1 POWER SWITCH CONTROL
A power switch control is used in order to limit the inrush
current when plugging the reader into the bus. The main
decoupling capacitor is connected to the output of this
power switch control (pin V_DD).
8.2.2 3.3 V REGULATOR
The output voltage of the 3.3 V linear regulator is used for:
• Powering-up the microcontroller and the ISO7816
UART
• It is the reference voltage for the signalling pull-up
resistor connected to pin D+.
If this voltage is used within the application, the current
should not exceed 10 mA.
For stability reasons, a 1 µF low ESR decoupling capacitor
is needed between the output of the regulator (V_DDD) and
the specific regulator ground (DGND).
For programming the EPROM of the TDA8030; TDA8031,
by applying a logic 1 to pin CPROG it will disable the
regulator, so that the microcontroller will be powered-up at
5 V.
8.2.3 DC-TO-DC CONVERTER
In case of a 5 V card, the card buffers are supplied by an
inductive DC-to-DC converter.
In case of a 3 or 1.8 V card, the DC-to-DC converter is
transparent and the card buffers are then supplied directly
by V_DD.
The external components for the DC-to-DC converter
should be an inductance of 6.8 µH, a low ESR capacitor of
1 µF and a Schottky diode (type BAT54).
The power efficiency is approximately 85% up to
I_CC = 55 mA. The current is limited at 100 mA during the
start-up phase to avoid spurious supply drop-outs.
The DC-to-DC converter is transparent for a 3 V card.
handbook, full pagewidth
VDD
LX
clock
N drive
reset
low
P drive
up
VUP
2003 Jul 04
Vref
Fig.7 DC-to-DC converter.
29
MGU887