LM3208TL/NOPBPB National Semiconductor, LM3208TL/NOPBPB Datasheet - Page 12

• Manufacturer Part Number: LM3208TL/NOPBPB
• Manufacturer: National Semiconductor

Specifications of LM3208TL/NOPBPB

• Lead Free Status / Rohs Status: Supplier Unconfirmed

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Block Diagram
Operation Description
The LM3208 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 Li-Ion battery cell. It is based on a current-
mode buck architecture, with synchronous rectification for
high efficiency. It is designed for a maximum load capability
of 650mA when V
Maximum load range may vary from this depending on input
voltage, output voltage and the inductor chosen.
Efficiency is typically around 95% for a 400mA load with 3.4V
output, 3.9V input. The LM3208 has an R
scheme to increase efficiency when V
voltage is dynamically programmable from 0.8V to 3.6V by
adjusting the voltage on the control pin without the need for
external feedback resistors. This prolongs battery life by
changing the PA supply voltage dynamically depending on
its transmitting power.
<
1.00V (typ.) in PWM mode.
OUT
>
1.05V (typ.) and 400mA when V
OUT
DSON
≤ 1V. The output
FIGURE 2. Functional Block Diagram
management
OUT
12
Additional features include current overload protection and
thermal overload shutdown.
The LM3208 is constructed using a chip-scale 8-pin micro
SMD package. This package offers the smallest possible
size, for space-critical applications such as cell phones,
where board area is an important design consideration. Use
of a high switching frequency (2MHz, typ.) reduces the size
of external components. As shown in Figure 1, only three
external power components are required for implementation.
Use of a micro SMD package requires special design con-
siderations for implementation. (See Micro SMD Package
Assembly and use in the Applications Information section.)
Its fine bump-pitch requires careful board design and preci-
sion assembly equipment. Use of this package is best suited
for opaque-case applications, where its edges are not sub-
ject to high-intensity ambient red or infrared light. In addition,
the system controller should set EN low during power-up and
other low supply voltage conditions. (See Shutdown Mode in
the Device Information section.)
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