Datasheet

TPS7301Q, TPS7325Q, TPS7330Q, TPS7333Q, TPS7348Q, TPS7350Q
LOW-DROPOUT VOLTAGE REGULATORS
WITH INTEGRATED DELAYED RESET FUNCTION
SLVS124F – JUNE 1995 – REVISED JANUARY 1999
39
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
undervoltage supervisor function (continued)
Transient loads or line pulses can also cause a reset to occur if proper care is not taken in selecting the input
and output capacitors. Load transients that are faster than 5 µs can cause a reset if high-ESR output capacitors
(greater than approximately 7 Ω) are used. A 1-µs transient causes a reset when using an output capacitor with
greater than 3.5 Ω of ESR. Note that the output-voltage spike during the transient can drop well below the reset
threshold and still not trip if the transient duration is short. A 1-µs transient must drop at least 500 mV below the
threshold before tripping the reset circuit. A 2-µs transient trips RESET
at just 400 mV below the threshold.
Lower-ESR output capacitors help by reducing the drop in output voltage during a transient and should be used
when fast transients are expected.
NOTE:
V
IT+
= V
IT–
+Hysteresis
output noise
The TPS73xx has very low output noise, with a spectral noise density < 2 µV/√Hz. This is important when
noise-susceptible systems, such as audio amplifiers, are powered by the regulator.
regulator protection
The TPS73xx PMOS-pass transistor has a built-in back diode that safely conducts reverse currents when the
input voltage drops below the output voltage (e.g., during power down). Current is conducted from the output
to the input and is not internally limited. If extended reverse voltage is anticipated, external limiting might be
appropriate.
The TPS73xx also features internal current limiting and thermal protection. During normal operation, the
TPS73xx limits output current to approximately 1 A. When current limiting engages, the output voltage scales
back linearly until the overcurrent condition ends. While current limiting is designed to prevent gross device
failure, care should be taken not to exceed the power dissipation ratings of the package. If the temperature of
the device exceeds 165°C, thermal-protection circuitry shuts it down. Once the device has cooled, regulator
operation resumes.