TCA5013 Datasheet, PDF (37/68 Pages) Texas Instruments – Feature Rich Smartcard Interface IC

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TCA5013
SCPS253B – JANUARY 2014 – REVISED JANUARY 2016
It is possible that the supervisor fault is asserted during power up If V_DDI ramps before V_DD (depending on the
V_DD ramp rate). If V_DD is ramped and stable before V_DDI is ramped, the supervisor fault will not be asserted.
Figure 18 shows the operation of voltage supervisor for various combinations of V_DD and V_DDI.
V_DDTH
V_DDSH
V_DDITH
VDD > VDDSH
V_DDI < V_DDITH.
Device stays in
power down
mode
Supervisor fault
is asserted
VDD < VDDSH
V_DDI > V_DDITH.
Device is in
power down
mode
Supervisor
fault is cleared
V_DD > V_DDSH
VDDI > VDDITH.
Device comes
out of POR
Supervisor fault
is cleared
V_DDTH>V_DD > V_DDSH
V_DDI > V_DDITH.
Device comes out
of POR.
Supervisor fault is
asserted.
V_DD > V_DDTH
VDDI > VDDITH.
Device comes
out of POR
VDD > VDDTH
V_DDI < V_DDITH.
Device is enters
power down
mode
VDD < VDDSH
V_DDI > V_DDITH.
Device enters
power down
mode
Figure 18. Voltage Supervisor Operation
8.4.10.2 DC-DC Boost
TCA5013 contains a DC-DC boost circuit that can step up V_DD voltage to generate the required card V_CC. The
boost requires an external diode (D_VUP) as a high side switch. It also requires an external inductor (L_VDD) in
series with the VDD pin. The normal switching frequency of the boost is ~2.4 Mhz. The boost is rated for 180
mA. This implies that the sum of the current drawn on individual card VCC pins cannot exceed 180 mA. If
exceeded it could result in the card V_CC falling out of the operating range defined in Electrical
Characteristics—Power Supply and ESD.
The DC_DC bit (Reg 0x42; Bit [7]) can be used to disable the DC-DC boost circuit. The DC-DC boost should be
disabled only in systems where the supply is always guaranteed to be at least 0.25V greater than maximum card
V_CC supported on that system, for example, if 5 V cards need to be supported in a system the DC-DC boost can
be disabled if V_DD is guaranteed to be above 5.25 V. In systems where DC-DC is not used, the VDD pin shall be
shorted to VUP pin. The LX pin should shorted to GNDP. Shorting to GNDP is recommended to prevent
switching noise from impacting rest of system. Note that LX shall not be connected to anything other than GNDP
in order to prevent excess power loss and/or damage to the part. If DC-DC boost is disabled and the V_DD is not
sufficient to activate a card interface at the voltage set by SET_VCC (Reg 0x01, Reg 0x11, Reg 0x21, Reg 0x31;
bit [7:6]), it will result in a V_CC ramp fault (See V_CC Ramp Fault).
The DC-DC boost is always disabled in standby mode (See Standby Mode). When a card activation command is
received, the DC-DC boost circuit is enabled by the digital core. The boost output voltage depends on voltage at
which the card needs to be activated, that is, based on SET_VCC (Reg 0x01, Reg 0x11, Reg 0x21, Reg 0x31;
bit [7:6]). For 1.8-V and 3-V card activation, the boost output voltage will be ~3.5 V. For 5-V card activations the
boost output voltage will be ~5.5 V. In a scenario where a 3 V or 1.8 V card is active and an I²C command is
received to activate another card with 5 V, the boost output voltage will go up to 5.5 V and the card LDOs (See
LDOs and Load Transient Response) on the already active card interface, will keep the card V_CC within
regulation.
Under light load conditions, the DC-DC boost can enter pulse skipping mode in order to improve efficiency. In
pulse skipping mode, the switching frequency is not constant and will be much lower than the normal switching
frequency of 2.4 MHz.
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