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APPLICATION INFORMATION
TPS71533
IN
OUT
V
IN
V
OUT
C1
0.1
μ
F
0.47
μ
F
GND
External Capacitor Requirements
Although not required, a 0.047-μF or larger input bypass capacitor, connected between IN and GND and located
close to the device, is recommended to improve transient response and noise rejection of the power supply as a
whole. A higher-value input capacitor may be necessary if large, fast-rise-time load transients are anticipated and
the device is located several inches from the power source.
Power Dissipation and Junction Temperature
To ensure reliable operation, worst-case junction temperature should not exceed 125°C. This restriction limits the
power dissipation the regulator can handle in any given application. To ensure the junction temperature is within
acceptable limits, calculate the maximum allowable dissipation, P
D(max)
, and the actual dissipation, P
D
, which
must be less than or equal to P
D(max)
.
The maximum-power-dissipation limit is determined using the following equation:
PD(max)
TJmax
TA
RJA
(1)
P
D
V
IN
V
OUT
I
OUT
(2)
Regulator Protection
The TPS715xx PMOS-pass transistor has a built-in back diode that conducts reverse current 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 operation is anticipated, external limiting might be
appropriate.
TPS715xx
SLVS338L–MAY 2001–REVISED SEPTEMBER 2005
The TPS715xx family of LDO regulators has been optimized for ultra-low power applications such as the
MSP430 microcontroller. Its ultra-low supply current maximizes efficiency at light loads, and its high input voltage
range makes it suitable for supplies such as unconditioned solar panels.
Figure 13. Typical Application Circuit (Fixed Voltage Version)
The TPS715xx requires an output capacitor connected between OUT and GND to stabilize the internal control
loop. Any capacitor (including ceramic and tantalum)
≥
0.47 μF properly stabilizes this loop. X7R type capacitors
are recommended but X5R and others may be used.
where:
The regulator dissipation is calculated using:
T
J
max is the maximum allowable junction temperature.
R
θ
JA
is the thermal resistance junction-to-ambient for the package (see the Dissipation Ratings table).
T
A
is the ambient temperature.
For a higher power package version of the TPS715xx, see the
.The TPS715xx features internal current limiting. During normal operation, the TPS715xx limits output current to
approximately 500 mA. When current limiting engages, the output voltage scales back linearly until the
overcurrent condition ends. Take care not to exceed the power dissipation ratings of the package.