Telecom__48_to_5_V_at_05_A

Published:2009/7/24 9:04:00 Author:Jessie | From:SeekIC

The small current consumption of a MAX641 allows the IC to be biased at a -50-V rail with a shunt zener so that the IC can convert -50 to +5 V. This is a common requirement in telecom systems, where logic circuits must be powered from the central-office battery voltage. A small high-voltage pnp level-shifts the feedback signal from the + 5-V output down to the pin MAX641, where the ground pin is tied to the 50-V input (instead of true ground). This is done so that EXT can drive the MOSFET to switch the inductor to -50 V, making the circuit operate similar to a step-up dc/dc converter. The 330-pF capacitor provides feed-forward compensation to stabilize the regulator control loop.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/Telecom__48_to_5_V_at_05_A.html

Print this Page | Comments | Reading(3)