ZHCSCU3C January 2014 – September 2019 TCA5013
PRODUCTION DATA.
TCA5013 contains a DC-DC boost circuit that can step up VDD voltage to generate the required card VCC. The boost requires an external diode (DVUP) as a high side switch. It also requires an external inductor (LVDD) 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 VCC 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 VCC 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 VDD 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 VDD 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 VCC ramp fault (See VCC 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 VCC 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.