AMG-SO204 Datasheet, PDF (27/30 Pages) alpha microelectronics gmbh – Optical Switch IC

AMG-SO204
Optical Switch IC
internal. The use of two bandgaps has been dictated by precision and voltage considerations:
the high-voltage bandgap is less precise but can operate under a relatively wide range of
supply voltages (4.5V...6.5V), whereas the low-voltage bandgap is more precise but requires
an accurate supply voltage of 3.3V. The high voltage bandgap provides the reference voltage
for the 3.3V voltage regulator and the low voltage bandgap the reference for the 2.5V and
1.8V voltage regulators.
The IC includes four low-drop voltage regulators. The 3.3V regulator lowers the supply voltage
to about 3.3V. This regulated voltage is used to supply two on-chip 2.5V regulators, the low-
voltage voltage bandgap, the on-chip 1.8V regulator, and any off-chip 3.3V electronics. The
two 2.5V regulators supply, independently, the analog and the digital part of the IC and the
bias current generator. The use of two virtually identical 2.5V regulators was dictated by the
desire to achieve high separation between the (quiet) analog and the (noisy) digital part of the
IC. The 1.8V regulator is used to provide the reference voltage for the ADC. The voltage
regulators whose output voltage are extern available at the pins CB3V3, VDDA, VDDD and
VREF and the supply pin VDD needs to be decoupled.
The cell bias currents provides a current of about 15uA to each ADC.
AMG-SO204 Revision: A
29. Jul. 2010 © All rights reserved Page 27 of 30