Typical Performance Characteristics

Efficiency vs Output Voltage

(PWM MODE, with Diode)

20036730

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).

ciency is typically 96% for a 200mA load with 3.6V output,

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.

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