TCA5013 Datasheet, PDF (38/68 Pages) Texas Instruments – Feature Rich Smartcard Interface IC

TCA5013
SCPS253B – JANUARY 2014 – REVISED JANUARY 2016
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8.4.10.3 LDOs and Load Transient Response
The TCA5013 has an internal LDO that generates a stable supply for the internal circuits. The input to the
internal LDO is V_DD. The output of the internal LDO is connected to the LDOCAP pin. A 1 uF decoupling
capacitor shall be connected to the LDOCAP pin to ensure proper device operation. The internal LDO voltage is
typically 2.65 V but can be lower if V_DD is not sufficient.
In addition to the internal LDO, the TCA5013 has a dedicated LDO per card interface to generate the V_CC for that
card interface (here on forth, these LDOs are referred to as card LDOs). The card LDOs provide the power
supply for smartcard operation. During the normal operation of the smartcard, the LDO output is subject to load
transients. The EMV4.3 standard defines a load transient envelope shown in Figure 19. The card LDOs are able
to handle these transients, while keeping V_CC within limits defined in Electrical Characteristics—Card V_CC. An
external 200 nF capacitor shall be connected to their card VCC pins (VCCUC, VCCCS1, VCCS2, VCCS3) to
ensure proper load transient response by the card LDOs.
5V
3V
1.8V
Figure 19. Load Transients defined by EMV4.3
The card LDOs are enabled only when the card interface is activated (see Active Mode). The output voltage is
determined by the card interface settings registers (Reg 0x01, Reg 0x11, Reg 0x21, Reg 0x31). At the start of
the activation sequence, the card LDO is enabled and starts to ramp to the voltage defined in the corresponding
card interface settings register. Once the LDO has been enabled, any changes to the card interface settings
registers will not have any effect on the LDO output voltage. The card also LDOs also have short circuit
protection. When the current drawn exceeds ~150 mA (typ.) the LDO automatically shuts down and the card
interface is deactivated (see Deactivation Sequence).
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