LM2706 Datasheet, PDF (1/15 Pages) National Semiconductor (TI) – Miniature, Variable, Step-Down DC-DC Converter with Bypass for RF Power Amplifiers

PRELIMINARY
February 2004
LM2706
Miniature, Variable, Step-Down DC-DC Converter with
Bypass for RF Power Amplifiers
General Description
The LM2706 DC-DC converter is optimized for powering RF
power amplifiers (PAs) from a single Lithium-Ion cell. It may
also be used in many other applications. It steps down an
input voltage from 2.7V to 5.5V to a variable output from
1.5V to 3.25V up to 300 mA. Output voltage is set using a
V_CON analog input for controlling power levels and efficiency
of the RF PA. An internal bypass switch allows direct con-
nection to the battery for maximum power to the RF PA.
The device offers 4 modes for mobile phones and similar RF
PA applications. Fixed-frequency PWM mode minimizes RF
interference. Forced Bypass mode turns on an internal by-
pass switch to power the PA directly from the battery. Auto-
matic bypass mode minimizes dropout by turning on the
bypass switch when the battery decays to near the output
voltage. Shutdown mode turns the device off and reduces
battery consumption to 0.1 µA (typ.).
The device also offers internal synchronous rectification for
high efficiency (95% typ at 3.25 V_OUT, 200 mA, 3.9 V_IN).
Current limit and thermal overload protection protects the
device and system during fault conditions.
The LM2706 is available in a 10-pin lead free micro SMD
package. This packaging uses National’s chip-scale micro
SMD technology and offers the smallest possible size. A high
switching frequency (600 kHz) allows use of tiny surface-
mount components. Only three small external surface-mount
components, an inductor and two ceramic capacitors, are
required.
n ±2% DC output voltage precision
n Internal 105 mΩ (typ) bypass switch
n 300 mA maximum load capability
n 1.4 mA typ quiescent current
n 0.1 µA typ shutdown current
n 600 kHz PWM switching frequency
n High efficiency (95% typ at 3.9 V_IN, 3.25 V_OUT at
200 mA) from internal synchronous rectification
Features
n Forced and Automatic Bypass modes
n Miniature 10-pin lead free micro SMD package
n Only three tiny surface-mount external components
required
n Uses small ceramic capacitors
n Low output voltage ripple (<10 mV typ)
n Internal soft start
n Current overload protection
n No external compensation
Applications
n Mobile Phones
n Hand-Held Radios
n RF PC Cards
n Battery Powered RF Devices
Key Specifications
n Operates from a single LiION cell (2.7V to 5.5V)
n Variable output voltage (1.5V to 3.25V)
Typical Application Circuit
© 2004 National Semiconductor Corporation DS200409
20040901
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