REGULATED_LOW_NOISE_VOLTAGE_INVERTER

Published:2009/7/14 11:25:00 Author:May | From:SeekIC

Analog cell phones rely on a quiet GaAsFET bias supply to maximize the signal-to-noise ratio, providing a high-quality transmission. The LTC 1551CS8-4. 1 switched-capacitor voltage inverter circuit shown reduces output noise to less than 1 mV on the -4.1-V regulated output voltage. The 900-kHz operating frequency allows the charge pump to use small 0.l-μF capacitors. The 10-μF and 0.1-μF output capacitors effectively reduce the 900-kHz ripple noise to relatively insignificant levels. The LTZ1550CS8-4.1 has an active low shutdown input (SHDN), whereas its counterpart, the LTC1551CS8-4.1, has an active high shutdown input. This choice minimizes component count.The LTC1550 and 1551CS8-4.1 both operate in doubler mode, meaning that they only invert the input voltage and regulate it down to -4.1 V. The input voltage range is 4.5 to 7 V.



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