Datasheet

t =
(120 R )
(120+R )
L
L
·
·
C
OUT
TLV707 Series
SBVS153C –FEBRUARY 2011–REVISED NOVEMBER 2012 www.ti.com
APPLICATION INFORMATION
GENERAL DESCRIPTION IMPROVE PSRR AND NOISE PERFORMANCE
The TLV707 series (TLV707xx and TLV707xxP) Input and output capacitors should be placed as
belongs to a new family of next-generation value low- close to the device pins as possible. To improve ac
dropout regulators (LDOs). These devices consume performance such as PSRR, output noise, and
low quiescent current and deliver excellent line and transient response, it is recommended that the board
load transient performance. These characteristics, be designed with separate ground planes for V
IN
and
combined with low noise and very good PSRR with V
OUT
, with the ground plane connected only at the
little (V
IN
– V
OUT
) headroom, make this family of GND pin of the device. In addition, the ground
devices ideal for portable RF applications. connection for the output capacitor should be
connected directly to the GND pin of the device. High
This family of regulators offers current limit and
ESR capacitors may degrade PSRR performance.
themal protection. The operating junction temperature
of these devices is –40°C to +125°C.
INTERNAL CURRENT LIMIT
INPUT AND OUTPUT CAPACITOR The TLV707 internal current limit helps to protect the
REQUIREMENTS regulator during fault conditions. During current limit,
the output sources a fixed amount of current that is
Generally, 1.0-µF X5R- and X7R-type ceramic
largely independent of the output voltage. In such a
capacitors are recommended because these
case, the output voltage is not regulated, and is V
OUT
capacitors have minimal variation in value and
= I
LIMIT
× R
LOAD
. The PMOS pass transistor dissipates
equivalent series resistance (ESR) over temperature.
(V
IN
– V
OUT
) × I
LIMIT
until thermal shutdown is
triggered and the device turns off. As the device
However, the TLV707 is designed to be stable with
cools, it is turned on by the internal thermal shutdown
an effective capacitance of 0.1 µF or larger at the
circuit. If the fault condition continues, the device
output. Thus, the device is stable with capacitors of
cycles between current limit and thermal shutdown.
other dielectric types as well, as long as the effective
See the Thermal Information section for more details.
capacitance under operating bias voltage and
temperature is greater than 0.1 µF. This effective
The PMOS pass element in the TLV707 has a built-in
capacitance refers to the capacitance that the LDO
body diode that conducts current when the voltage at
sees under operating bias voltage and temperature
OUT exceeds the voltage at IN. This current is not
conditions; that is, the capacitance after taking both
limited, so if extended reverse voltage operation is
bias voltage and temperature derating into
anticipated, external limiting to 5% of the rated output
consideration. In addition to allowing the use of
current is recommended.
cheaper dielectrics, this capability of being stable with
0.1-µF effective capacitance also enables the use of
SHUTDOWN
smaller footprint capacitors that have higher derating
in size- and space-constrained applications.
The enable pin (EN) is active high. The device is
enabled when voltage at the EN pin goes above 0.9
NOTE: Using a 0.1-µF rated capacitor at the output
V. This relatively lower voltage value required to turn
of the LDO does not ensure stability because the
on the LDO can also be used to power the device
effective capacitance under the specified operating
when it is connected to a GPIO of a newer processor,
conditions would be less than 0.1 µF. Maximum ESR
where the GPIO Logic 1 voltage level is lower than
should be less than 200 mΩ.
that of traditional microcontrollers. The device is
Although an input capacitor is not required for turned off when the EN pin is held at less than 0.4 V.
stability, it is good analog design practice to connect When shutdown capability is not required, EN can be
a 0.1-μF to 1.0-μF, low ESR capacitor across the IN connected to the IN pin.
pin and GND pin of the regulator. This capacitor
The TLV707xxP version has internal active pull-down
counteracts reactive input sources and improves
circuitry that discharges the output with a time
transient response, noise rejection, and ripple
constant of:
rejection. A higher-value capacitor may be necessary
if large, fast rise-time load transients are anticipated,
or if the device is not located close to the power
source. If source impedance is more than 2-Ω, a 0.1-
where:
μF input capacitor may be necessary to ensure
stability. • R
L
= Load resistance
• C
OUT
= Output capacitor (1)
BOARD LAYOUT RECOMMENDATIONS TO
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