Texas Instruments TPS54980EVM-022, User Manual

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Background
1-2
1.1 Background
The TPS54980 tracking dc/dc converter is designed to provide accurate
power sequencing in applications where two or more voltages are required for
a load. These types of applications include core and I/O power supplies for
microprosessors, DSPs, and FPGAs. Typically, some specific relation
between the core and I/O supply voltages has to be provided during the power
up and power down sequences. The TPS54980 tracking dc/dc converter is
capable of direct tracking, ratiometric tracking, and voltage sequencing with
a second power source.
The TPS54980EVM−022 is a two-channel EVM demonstrating the flexibility
inherent in the TPS54980 design for tracking and sequencing core and I/O
voltages. The TPS54980 is used to generate the core voltage and is nominally
set at 1.8 V. The nominal 3.3-V I/O voltage is provided by a TPS2013
distribution switch. Rated input voltage and output current range are listed in
Table 1−1.
Table 1−1. Input Voltage and Output Current Summary
EVM Input Voltage Range Output Current Range
TPS54980EVM−022 3.0 V to 4.0 V
Core, −9 A to 9 A
TPS54980EVM−022 3.0 V to 4.0 V
I/O, 0 to 1.5 A
This evaluation module is designed to demonstrate the small PCB areas that
may be achieved when designing with the TPS54980 regulator. The switching
frequency is set at a nominal 700 kHz, allowing the use of a small footprint
0.65-
µ
H output inductor.
The MOSFETs of the TPS54980 are incorporated inside the TPS54980
package. This eliminates the need for external MOSFETs and their associated
drivers. The low drain-to-source on resistance of the MOSFETs provides the
TPS54980 high efficiency and helps to keep the junction temperature low at
high output currents.The compensation components are provided external to
the IC and allow for an adjustable output voltage and a customizable loop
response.
The TPS54980 device uses the TRACKIN pin to access the tracking and
sequencing capabilities. An internal multiplexer circuit compares the voltage
at this pin with the internal reference voltage and uses the lesser of the two as
the reference for the output voltage regulation. When the output of another
power supply or distribution switch is connected to the TRACKIN pin of the
TPS54980, the output of the TPS54980 tracks the output of this other channel
during power up or power down, until the voltage at the TRACKIN pin becomes
higher than the internal reference voltage. By applying the other power supply
output to the TRACKIN pin through an appropriate resistor divider network,
any required power up and power down relation between the two output
voltages of the regulators can be set by changing the ratio of the divider
network.