LP5910 datasheet(15/31 Pages) TI

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8.2.2.6 No-Load Stability

The LP5910 remains stable, and in regulation, with no external load.

8.2.2.7 Enable Control

The LP5910 may be switched to an ON or OFF state by a logic input at the EN pin. A voltage on this pin greater

than VIH turns the device on, while a voltage less than VIL turns the device off.

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

an output pulldown circuit is activated which ensures that any charge stored on COUT is discharged 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-MΩ 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 turn-on/off voltage thresholds listed in the Electrical Characteristics under VIL and

VIH.

Table 8-2. Recommended Output Capacitor Specification

PARAMETER

TEST CONDITIONS

MIN

NOM

MAX

UNIT

Output capacitor, COUT

Capacitance for stability

0.7

µF

ESR

500

mΩ

8.2.2.8 Power Dissipation

Knowing the device power dissipation and proper sizing of the thermal plane connected to the tab or pad is

critical to ensuring reliable operation. Device power dissipation depends on input voltage, output voltage, and

load conditions and can be calculated with Equation 1.

PD(MAX) = (VIN(MAX) – VOUT) × IOUT(MAX)

(1)

Power dissipation can be minimized, and greater efficiency can be achieved, by using the lowest available

voltage drop option that would still be greater than the dropout voltage (VDO). However, keep in mind that higher

voltage drops result in better dynamic (that is, PSRR and transient) performance.

On the WSON (DRV) package, the primary conduction path for heat is through the exposed power pad to the

PCB. To ensure the device does not overheat, connect the exposed pad, through thermal vias, to an internal

ground plane with an appropriate amount of copper PCB area .

On the DSBGA (YKA) package, the primary conduction path for heat is through the four bumps to the PCB.

The maximum allowable junction temperature (TJ(MAX)) determines maximum power dissipation allowed

(PD(MAX)) for the device package.

Power dissipation and junction temperature are most often related by the junction-to-ambient thermal resistance

(RθJA) of the combined PCB and device package and the temperature of the ambient air (TA), according to

Equation 2 or Equation 3:

TJ(MAX) = TA(MAX) + (RθJA × PD(MAX))

(2)

PD(MAX) = (TJ(MAX) - TA(MAX)) / RθJA

(3)

Unfortunately, this RθJA is highly dependent on the heat-spreading capability of the particular PCB design,

and therefore varies according to the total copper area, copper weight, and location of the planes. The RθJA

recorded in Thermal Information is determined by the specific EIA/JEDEC JESD51-7 standard for PCB and

copper-spreading area, and is to be used only as a relative measure of package thermal performance. For

a well-designed thermal layout, RθJA is actually the sum of the package junction-to-case (bottom) thermal

resistance (RθJCbot) plus the thermal resistance contribution by the PCB copper area acting as a heat sink.

www.ti.com

LP5910

SNVSA91F – SEPTEMBER 2015 – REVISED APRIL 2021

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