![](http://datasheet.mmic.net.cn/120000/TPS84410RKGT_datasheet_3584279/TPS84410RKGT_16.png)
SLVSAR5
– SEPTEMBER 2011
Power Good (PWRGD)
The PWRGD pin is an open drain output. Once the voltage on the SENSE+ pin is between 93% and 105% of the
set voltage, the PWRGD pin pull-down is released and the pin floats. The recommended pull-up resistor value is
between 10 k
Ω and 100 kΩ to a voltage source that is 6 V or less. The PWRGD pin is in a defined state once
VIN is greater than 1.2 V, but with reduced current sinking capability. The PWRGD pin achieves full current
sinking capability once the VIN pin is above 2.95V.
Figure 21 shows the PWRGD waveform during power-up.
The PWRGD pin is pulled low when the voltage on SENSE+ is lower than 91% or greater than 107% of the
nominal set voltage. Also, the PWRGD pin is pulled low if the input UVLO or thermal shutdown is asserted, or if
the INH pin is pulled low.
Power-Up Characteristics
When configured as shown in the front page schematic, the TPS84410 produces a regulated output voltage
following the application of a valid input voltage. During the power-up, internal soft-start circuitry slows the rate
that the output voltage rises, thereby limiting the amount of in-rush current that can be drawn from the input
source. The soft-start circuitry introduces a short time delay from the point that a valid input voltage is
recognized.
Figure 21 shows the start-up waveforms for a TPS84410, operating from a 5-V input and with the
output voltage adjusted to 1.8 V. The waveform is measured with a 2-A constant current load.
Figure 21. Start-Up Waveforms
Remote Sense
The SENSE+ pin must be connected to VOUT at the load, or at the device pins.
Connecting the SENSE+ pin to VOUT at the load improves the load regulation performance of the device by
allowing it to compensate for any I-R voltage drop between its output pins and the load. An I-R drop is caused by
the high output current flowing through the small amount of pin and trace resistance. This should be limited to a
maximum of 300 mV.
NOTE
The remote sense feature is not designed to compensate for the forward drop of nonlinear
or frequency dependent components that may be placed in series with the converter
output. Examples include OR-ing diodes, filter inductors, ferrite beads, and fuses. When
these components are enclosed by the SENSE+ connection, they are effectively placed
inside the regulation control loop, which can adversely affect the stability of the regulator.
16
Copyright
2011, Texas Instruments Incorporated