LM2706 Datasheet | National Semiconductor

LM2706 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 m A. Output voltage is set using a .. VCON analog input for controlling power levels and efficiency of the RF PA. An internal bypass switch allows direct connection 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 bypass switch to power the PA directly from the battery. Automatic 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 VOUT, 200 m A, 3.9 VIN). 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 k Hz) allows use of tiny surfacemount ponents. Only three small external surface-mount ponents, an inductor and two ceramic capacitors, are required. n n n n n n n ± 2% DC output voltage precision Internal 105 mΩ (typ) bypass switch 300 m A maximum load capability 1.4 m A typ quiescent current 0.1 µA typ shutdown current 600 k Hz PWM switching frequency High efficiency (95% typ at 3.9 VIN, 3.25 VOUT at 200 m A) from internal...