National Semiconductor has introduced a new generation of seven low dropout (LDO) regulators designed to meet the unique power management needs of digital processor, analog and RF subsystems. The new LDOs are optimised for cellphones, notebooks, PDAs, MP3 players and other handheld portable systems. They are also suited for use in wireless LANs, medical and industrial equipment.
In the past, designers had to choose a general-purpose LDO to meet system requirements. Using the new LP399x family of products, designers now have a portfolio of LDOs customised to meet the power needs of digital loads or RF and analog loads in mobile and handheld devices. With their small size, ultra-low dropout voltages and lower current usage during standby mode, National says these new CMOS linear regulators enable designers to create smaller devices with longer battery life.
LDOs for microcontrollers, DSPs, and other digital cores
To power digital cores, designers require excellent line and load transient response with sub-1 microfarad ceramic capacitors, output voltages as low as 0,8 V as well as fast turn on-off times while consuming very little operating current. National's new products are:
* LP3990 - a 150 mA CMOS linear regulator with preset output between 3,3 V and 0,8 V. Offers an ideal balance between fast load transient response and low operating current. The LP3990 works without a reference bypass capacitor, saving space and reducing bill of materials.
* LP3992 - a 30 mA CMOS linear regulator designed for digital loads, particularly well suited to power applications such as Bluetooth baseband devices, where the controlled turn-on/turn-off times ensure the digital device does not fall into non-defined states.
* LP3993 - 80 mA CMOS linear regulator offers very low operating current for mobile applications where fast start-up and good line and load regulation are important. Operating current of 10 µA at 1 mA load significantly increases standby time.
* LP3993 also works without a bypass capacitor.
* LP3994 - 50 mA CMOS linear regulator designed for low operating current, low noise and accurate output voltage. Operates in the 2,5 V to 6,0 V input range and has a low operating current range of 20 µA when enabled. When disabled, device draws virtually zero current.
* LP3997 - 250 mA CMOS linear regulator supplies up to 500 mA peak output. 'Out-of-regulation' error flag indicates when the device's output is below the nominal voltage.
LDOs for powering RF and analog circuitry for mobile devices
To power RF loads, designers require low noise, excellent power supply rejection ration (PSRR) and low dropout. National's LP3995 and LP3999 complement the company's LP3985 family by extending the output voltage range down to 1,5 V and with lower noise, faster turn-on and active turn-off. These linear regulators are designed specifically for portable and wireless applications powered by Li-Ion and Ni-MH batteries. They offer device noise down to 25 µVrms, improved PSRR to above 60 dB at 1 kHz, dropout performance to 60 mV at 150 mA.
For more information contact Simon Churches, Arrow Altech Distribution, 011 923 9600, schurches@arrow.altech.co.za
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