lm2614btlx National Semiconductor Corporation, lm2614btlx Datasheet - Page 8

• Manufacturer Part Number: lm2614btlx
• Description: 400ma Sub-miniature Adjustable Dc-dc Converter Optimized For Rf Power Amplifiers
• Manufacturer: National Semiconductor Corporation

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Typical Performance Characteristics
LM2614ATL, Circuit of Figure 4, V
Device Information
The LM2614 is a simple, step-down DC-DC converter opti-
mized for powering RF power amplifiers (PAs) in mobile
phones, portable communicators, and similar battery pow-
ered RF devices. It is designed to allow the RF PA to operate
at maximum efficiency over a wide range of power levels
from a single LiION battery cell. It is based on a
current-mode buck architecture, with synchronous rectifica-
tion in PWM mode for high efficiency. It is designed for a
maximum load capability of 400mA (300mA for B grade) in
PWM mode. Maximum load range may vary from this de-
pending on input voltage, output voltage and the inductor
chosen.
The device has all three of the pin-selectable operating
modes required for powering RF PAs in mobile phones and
other sophisticated portable devices with complex power
management needs. Fixed-frequency PWM operation offers
full output current capability at high efficiency while minimiz-
ing interference with sensitive IF and data acquisition cir-
cuits. During standby operation, hysteretic PFM mode re-
duces quiescent current to 160µA typ. to maximize battery
life. Shutdown mode turns the device off and reduces battery
consumption to 0.02µA (typ).
DC PWM mode feedback voltage precision is
ciency is typically 96% for a 200mA load with 3.6V output,
IN
= 3.6V, T
A
Efficiency vs Output Voltage
= 25˚C, unless otherwise noted. (Continued)
±
(PWM MODE, with Diode)
1%. Effi-
8
3.9V input. The efficiency can be further increased by using
a schottky diode like MBRM120 as shown in Figure 4. PWM
mode quiescent current is 600µA typ. The output voltage is
dynamically programmable from 1.0V to 3.6V by adjusting
the voltage on the VCON at the external feedback resistors.
This ensures longer battery life by being able to change the
PA supply voltage dynamically depending on its transmitting
power.
Additional features include soft-start, current overload pro-
tection, over voltage protection and thermal shutdown pro-
tection.
The LM2614 is constructed using a chip-scale 10-pin thin
micro SMD package. This package offers the smallest pos-
sible size, for space-critical applications such as cell phones,
where board area is an important design consideration. Use
of a high switching frequency (600kHz) reduces the size of
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
Assembly and Use in the Application Information section.) Its
fine bump-pitch requires careful board design and precision
assembly equipment.
20036730
2
(375mm
2
).