Texas Instruments TPS65982 User Manual

11 Power Supply Recommendations
11.1 3.3-V Power
11.1.1 VIN_3V3 Input Switch
The VIN_3V3 input is the main supply to the TPS65982. The VIN_3V3 switch (S1 in Figure 9-40) is a
unidirectional switch from VIN_3V3 to LDO_3V3, not allowing current to flow backwards from LDO_3V3 to
VIN_3V3. This switch is on when 3.3 V is available. See Table 11-1 for the recommended external capacitance
on the VIN_3V3 pin.
11.1.2 VOUT_3V3 Output Switch
The VOUT_3V3 output switch (S2 in Figure 9-40) enables a low-current auxiliary supply to an external element.
This switch is controlled by and is off by default. The VOUT_3V3 output has a supervisory circuit that drives
the RESETZ output as a POR signal to external elements. RESETZ is also asserted by the MRESET pin or a
host controller. See RESETZ and MRESET for more details on RESETZ. See Table 11-1 for the recommended
external capacitance on the VOUT_3V3 pin.
11.1.3 VBUS 3.3-V LDO
The 3.3-V LDO from VBUS steps down voltage from VBUS to LDO_3V3. This allows the TPS65982 to be
powered from VBUS when VIN_3V3 is not available. This LDO steps down any recommended voltage on the
VBUS pin. When VBUS is 20 V, as is allowable by USB PD, the internal circuitry of the TPS65982 will operate
without triggering thermal shutdown; however, a significant external load on the LDO_3V3 pin may increase
temperature enough to trigger thermal shutdown. The VBUS 3.3-V LDO blocks reverse current from LDO_3V3
back to VBUS allowing VBUS to be unpowered when LDO_3V3 is driven from another source. See Table 11-1
for the recommended external capacitance on the VBUS and LDO_3V3 pins.
11.2 1.8 V Core Power
Internal circuitry is powered from 1.8 V. There are two LDOs that step the voltage down from LDO_3V3 to 1.8 V.
One LDO powers the internal digital circuits. The other LDO powers internal low voltage analog circuits.
11.2.1 1.8 V Digital LDO
The 1.8 V Digital LDO provides power to all internal low voltage digital circuits. This includes the digital core,
memory, and other digital circuits. See Table 11-1 for the recommended external capacitance on the LDO_1V8D
pin.
11.2.2 1.8 V Analog LDO
The 1.8 V Analog LDO provides power to all internal low voltage analog circuits. See Table 11-1 for the
recommended external capacitance on the LDO_1V8A pin.
11.3 VDDIO
The VDDIO pin provides a secondary input allowing some I/Os to be powered by a source other than LDO_3V3.
The default state is power from LDO_3V3. The memory stored in the flash will configure the I/O’s to use
LDO_3V3 or VDDIO as a source and application code will automatically scale the input and output voltage
thresholds of the I/O buffer accordingly. See I/O Buffers for more information on the I/O buffer circuitry. See Table
11-1 for the recommended external capacitance on the VDDIO pin.
11.3.1 Recommended Supply Load Capacitance
Table 11-1 lists the recommended board capacitances for the various supplies. The typical capacitance is the
nominally rated capacitance that must be placed on the board as close to the pin as possible. The maximum
capacitance must not be exceeded on pins for which it is specified. The minimum capacitance is minimum
capacitance allowing for tolerances and voltage de-rating ensuring proper operation.
TPS65982
SLVSD02E – MARCH 2015 – REVISED AUGUST 2021
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Texas Instruments TPS65982 Specifications

General

Brand	Texas Instruments
Model	TPS65982
Category	Motherboard
Language	English