Texas Instruments TPS7A53EVM-080, Руководство пользователя, Страница: 7 / 17

The slew rate of the load step can be adjusted by C16, R13, R14, and R16. In this section, only R14 and R16
are adjusted to set the slew rate. For a 1-mA to 3-A to 1-mA load step, use
Table 2-1 to select a value of R14
and R16 that results in the desired rise or fall time.
Table 2-1. Suggested Ramp Rate Resistor Values
R14 R16 Rise, Fall Time
90.9 kΩ 97.6 kΩ 20 µs
44.2 kΩ 47.5 kΩ 6 µs
28 kΩ 23.2 kΩ 3.3 µs
6.65 kΩ 5.9 kΩ 950 ns
After the EVM is modified (if needed), connect a power supply to banana connectors J24 (VDD) and J30 (GND)
with a 5-V DC supply and a 1-A DC current limit. As shown in
Figure 2-3 and Figure 2-4 , the TPS7A53A-Q1
transient response is very fast and the output voltage recovers in well under 1 ms after the initial load transient.
Use a pulse-duration limit of 1 ms to prevent excessive heating of the pulsed resistors (R8, R9, R10, R11, and
R12). Configure a function generator for the 50-Ω output, in a 0-V DC to 5-V DC square pulse. If necessary,
burst mode can be configured in the function generator for repetitive, low duty cycle, load transient testing.
A 20-kΩ resistor is installed on the EVM at R14, and a 20-kΩ resistor is installed on the EVM at R16. These
resistors provide approximately 1-A/μs slew rate from 1-mA to 3-A, and 1-A/μs slew rate from 3-A to 1-mA.
Figure 2-3 and Figure 2-4 provide example test data with R14 = 20 kΩ and R16 = 20 kΩ. The the red trace is the
output voltage and the green trace is the output current. R8, R9, R10, R11, and R12 provide 3-A of pulsed load.
The resulting test data shows a 1-mA to 3-A load step on VOUT of the LDO, with only a 47-μF capacitor on the
output of the LDO.
Figure 2-3. TPS7A53EVM-080 Load Transient
Results: 1-mA to 3-A Load Step
Figure 2-4. TPS7A53EVM-080 Load Transient
Results: 3-A to 1-mA Load Step
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SBVU078 – NOVEMBER 2022
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TPS7A53EVM-080 Evaluation Module 7
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