Datasheet

P
D
+
ǒ
V
IN
* V
OUT
Ǔ
I
OUT
P
D(max)
+
T
J
max * T
A
R
qJA
TPS715A33
IN OUT
V
IN
V
OUT
C1
0.1
µ
F
0.47
µ
F
GND
TPS715Axx
www.ti.com SBVS047F –MAY 2004–REVISED OCTOBER 2012
APPLICATION INFORMATION
The TPS715Axx family of LDO regulators has been optimized for ultra low-power applications such as the
MSP430 microcontroller. Its ultralow supply current maximizes efficiency at light loads, and its high input voltage
range makes it suitable for supplies such as unconditioned solar panels.
Figure 14. Typical Application Circuit (Fixed Voltage Version)
External Capacitor Requirements
Although not required, a 0.047μF 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
if the device is located several inches from the power source.
The TPS715Axx requires an output capacitor connected between OUT and GND to stabilize the internal control
loop. Any capacitor (including ceramic and tantalum) that is ≥ 0.47μF properly stabilizes this loop.
Power Dissipation and Junction Temperature
To ensure reliable operation, worst-case junction temperature should not exceed +150°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 Equation 1:
(1)
where:
T
J
max is the maximum allowable junction temperature.
R
θJA
is the thermal resistance junction-to-ambient for the package (see the Power Dissipation Rating table).
T
A
is the ambient temperature.
The regulator dissipation is calculated using Equation 2:
(2)
Power dissipation resulting from quiescent current is negligible.
Regulator Protection
The TPS715Axx PMOS-pass transistor has a built-in back diode that conducts reverse current when the input
voltage drops below the output voltage (for example, 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.
The TPS715Axx features internal current limiting. During normal operation, the TPS715Axx limits output current
to approximately 500mA. 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.
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