Dual LDOs keep power use and noise down

Oct. 27, 2005
Intersil’s ISL9000 offers 90dB PSRR at 1kHz and a quiescent current of 21µA/LDO for camera phones and digital still image sensors.

The ISL9000/11/12 family of LDOs (low drop out regulators) from Intersil is designed to better performance in noise-sensitive applications such as mobile camera phones and digital still camera image sensors. The highest PSRR (power supply rejection ratio) is needed to improve image quality, an increasingly important factor with the move towards megapixel resolutions.

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%, with a typical dropout of 200mV at 300mA. Separate enable pins control each individual LDO output. When both enable pins are low, the device is in shutdown, typically drawing less than 0.1µA.

The ISL9000 integrates output voltage sequencing and individual power-on-reset (POR) functions for each output so separate voltage monitoring/reset circuits are not needed. 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.

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