LM2619ATLX National Semiconductor, LM2619ATLX Datasheet - Page 8

• Manufacturer Part Number: LM2619ATLX
• Description: Conv DC-DC Single Step Down 2.8V to 5.5V 10-Pin uSMD T/R
• Manufacturer: National Semiconductor
• Type: Step Downr

Specifications of LM2619ATLX

• Package: 10uSMD
• Number Of Outputs: 1
• Minimum Input Voltage: 2.8 V
• Maximum Input Voltage: 5.5 V
• Switching Frequency: 500 to 1000 KHz
• Operating Supply Voltage: 2.8 to 5.5 V
• Maximum Output Current: 0.5 A
• Output Type: Adjustable
• Output Voltage: 1.5 to 3.6 V
• Switching Regulator: Yes
• Efficiency: 96(Typ) %
• Operating Temperature: -25 to 125 °C

www.national.com
Device Information
external components. Board area required for implementa-
tion is only 0.58in
Use of a micro-SMD package requires special design con-
siderations for implementation. (See Micro SMD Package
CIRCUIT OPERATION
Referring to Figure 4, Figure 5, Figure 6 and Figure 7,
the LM2619 operates as follows. During the first part of each
switching cycle, the control block in the LM2619 turns on the
internal PFET switch. This allows current to flow from the
input through the inductor to the output filter capacitor and
load. The inductor limits the current to a ramp with a slope of
(V
the second part of each cycle, the controller turns the PFET
switch off, blocking current flow from the input, and then
turns the NFET synchronous rectifier on. In response, the
inductor’s magnetic field collapses, generating a voltage that
forces current from ground through the synchronous rectifier
to the output filter capacitor and load. As the stored energy is
IN
–V
OUT
)/L, by storing energy in a magnetic field. During
2
(375mm
2
).
FIGURE 4. Typical Operating Circuit for 3.6V Output Voltage
(Continued)
8
Assembly and Use in the Application Information section.) Its
fine bump-pitch requires careful board design and precision
assembly equipment.
transferred back into the circuit and depleted, the inductor
current ramps down with a slope of V
current reaches zero before the next cycle, the synchronous
rectifier is turned off to prevent current reversal. The output
filter capacitor stores charge when the inductor current is
high, and releases it when low, smoothing the voltage across
the load.
The output voltage is regulated by modulating the PFET
switch on time to control the average current sent to the load.
The effect is identical to sending a duty-cycle modulated
rectangular wave formed by the switch and synchronous
rectifier at SW to a low-pass filter formed by the inductor and
output filter capacitor. The output voltage is equal to the
average voltage at the SW pin.
OUT
20057406
/L. If the inductor