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LDOs deliver ultra-high PSRR

Posted: 18 Oct 2005     Print Version  Bookmark and Share

Keywords:intersil  ldo  low dropout regulator  isl9000  isl9011 

Intersil Corp. announced a new family of high-performance dual low dropout regulators (LDOs) that promises ultra-high PSRR (power supply rejection ratio), extremely low quiescent current (Iq), and excellent noise performance for RF/noise-sensitive applications such as imaging sensors for digital still cameras or cellphone camera modules, MP3 players and portable medical and instrumentation devices.

According to Andrew Baker, product marketing manager of Intersil's handheld power products group, the ISL9000/11/12 family of LDOs offers a significant performance advantage to their customers in demanding noise-sensitive applications such as cellphone camera modules and digital still camera image sensors. "By using leading-edge technology, we offer a significant advantage over our competitors in overall solution size and provide the industry's best combination of ultra-high PSRR, very low noise, and low quiescent supply current to boost overall performance."

Baker explained that the highest PSRR is necessary to improve image quality, which is increasingly critical as they move toward megapixel resolutions in these applications.

The ISL9000 offers 90dB PSRR at 1KHz, and the quiescent current is typically 21µA/LDO when active. The output voltage accuracy over temperature is 1.8 percent with a drop-out of typically 200mV at 300mA. Separate enable pins control each individual LDO output; and when both enable pins are low, the device is in shutdown, typically drawing less than 0.1µA.

In addition, the ISL9000 integrates output voltage sequencing and individual power-on-reset (POR) functions for each output to remove the requirement for separate voltage monitoring/reset circuits. The POR delay for VO2 (voltage output) can be externally programmed by connecting a timing capacitor to the CPOR pin. The POR delay for VO1 is internally fixed at approximately 2ms to ensure voltage stability after start-up. A reference bypass pin is provided for connecting a noise filtering capacitor to increase the noise and PSRR performance.

Both the ISL9011 and ISL9012 are high-performance dual LDOs capable of sourcing 150mA current from channel 1mA and 300mA from channel 2. These devices have low standby current and are stable with output capacitance of 1µF to 10µF with ESR of up to 200 milliohms. A reference bypass pin allows an external capacitor for adjusting a noise filter for low-noise and high-PSRR applications.

The ISL9011 and ISL9012 offer PSRR of 70dB at 1kHz and quiescent current is typically 45µA with both LDOs enabled and active. Separate enable pins control each individual LDO output. When both enable pins are low, these devices are in shutdown mode, also typically drawing less than 0.1µA.

Several combinations of voltage outputs are standard on the ISL9000, ISL9011 and ISL9012, with output voltage options for each LDO ranging from 1.2V to 3.6V.

The ISL9000 is available in a 10-pin, Pb-free DFN package and is priced at $1.30; the ISL9011 is housed in a 10-pin, Pb-free DFN package and is priced at $1.10; and the ISL9012 is offered in a 10-pin, lead-free DFN package and is priced at $1.15. All prices are in 1,000-unit quantities.




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