15

LP5907

www.ti.com

SNVS798J – APRIL 2012 – REVISED MARCH 2016

Product Folder Links: LP5907

Submit Documentation Feedback

Copyright © 2012–2016, Texas Instruments Incorporated

The output capacitor must meet the requirement for the minimum value of capacitance and have an ESR value

that is within the range 5 m

Ω to 500 mΩ for stability. Like the input capacitor, the initial tolerance, applied voltage

de-rating, and temperature coefficient must all be considered when selecting the input capacitor to ensure the

actual capacitance is never less than 0.7 µF over the entire operating range.

8.2.2.5 Capacitor Characteristics

The LP5907 is designed to work with ceramic capacitors on the input and output to take advantage of the

benefits they offer. For capacitance values in the range of 1 µF to 10 µF, ceramic capacitors are the smallest,

least expensive and have the lowest ESR values, thus making them best for eliminating high frequency noise.

The ESR of a typical 1 µF ceramic capacitor is in the range of 20 m

Ω to 40 mΩ, which easily meets the ESR

requirement for stability for the LP5907.

A better choice for temperature coefficient in a ceramic capacitor is X7R. This type of capacitor is the most stable

and holds the capacitance within ±15% over the temperature range. Tantalum capacitors are less desirable than

ceramic for use as output capacitors because they are more expensive when comparing equivalent capacitance

and voltage ratings in the 1 µF to 10 µF range.

Another important consideration is that tantalum capacitors have higher ESR values than equivalent size

ceramics. This means that while it may be possible to find a tantalum capacitor with an ESR value within the

stable range, it would have to be larger in capacitance (which means bigger and more costly) than a ceramic

capacitor with the same ESR value. It should also be noted that the ESR of a typical tantalum increases about

2:1 as the temperature goes from 25°C down to –40°C, so some guard band must be allowed.

8.2.2.6 Remote Capacitor Operation

The LP5907 requires at least a 1-µF capacitor at the OUT pin, but there is no strict requirements about the

location of the capacitor in regards to the pin. In practical designs the output capacitor may be located up to 10

cm away from the LDO. This means that there is no need to have a special capacitor close to the output pin if

there is already respective capacitors in the system (like a capacitor at the input of supplied part). The remote

capacitor feature helps user to minimize the number of capacitors in the system.

As a good design practice, keep the wiring parasitic inductance at a minimum, which means to use as wide as

possible traces from the LDO output to the capacitors, keeping the LDO output trace layer as close to ground

layer as possible and avoiding vias on the path. If there is a need to use vias, implement as many as possible

vias between the connection layers. The recommendation is to keep parasitic wiring inductance less than 35 nH.

For the applications with fast load transients, it is recommended to use an input capacitor equal to or larger to

the sum of the capacitance at the output node for the best load transient performance.

8.2.2.7 No-Load Stability

The LP5907 remains stable, and in regulation, with no external load.

8.2.2.8 Enable Control

When the EN pin is low, the regulator output is off and the device typically consumes less than 1 µA.

to ground.

If the application does not require the use of the shutdown feature, the EN pin can be tied directly to the IN pin to

keep the regulator output permanently on.

An internal 1-M

Ω pulldown resistor ties the EN input to ground, ensuring that the device remains off if the EN pin

is left open circuit. To ensure proper operation, the signal source used to drive the EN pin must be able to swing

above and below the specified turnon or turnoff voltage thresholds listed in the Electrical Characteristics under