METHOD AND APPARATUS TO MINIMIZE SWITCHING NOISE DISBURBANCE

摘要

A power management circuit generates a reference voltage and distributes it to a plurality of independently-enabled regulator voltage reference circuits, each of which generates a predetermined voltage for a voltage regulator. Separate enable signals and enable pre-charge signals are distributed to each regulator voltage reference circuit. As a regulator voltage reference circuit is enabled via its associated enable signal, an enable pre-charge signal is also asserted for an initial duration. Each regulator voltage reference circuit includes a voltage setting circuit and a first current limiting transistor in series and operative to interrupt current to the voltage setting circuit when the regulator voltage reference circuit is disabled. A second current limiting transistor is configurably configured as a current mirror with the first current limiting transistor, and a pre-charge bias current from a current source passes through the second transistor. This limits the current through the first transistor and into the voltage setting circuit for the initial duration. After the initial duration, the current mirror is disabled and the first transistor is rendered fully conductive.

主权项

1. A power management circuit, comprising:
a main reference voltage circuit operative to generate a main reference voltage; a plurality of regulator voltage reference circuits, each receiving the main reference voltage and an enable signal, and each operative to output a signal having a predetermined voltage in response to the enable signal; wherein each regulator voltage reference circuit comprises
a voltage setting circuit operative to generate the predetermined voltage from the main reference voltage;a first current limiting transistor in series with the voltage setting circuit and operative to interrupt current to the voltage setting circuit in response to the enable signal;a second current limiting transistor proportionate in size to the first current limiting transistor;a switching network connecting the first and second current limiting transistors; anda control circuit operative to control the switching network to couple the first and second current limiting transistors as a current mirror configuration so as to limit current supplied to the voltage setting circuit for an initial duration when the regulator voltage reference circuit is enabled, and further operative to enable the first current limiting transistor and disable the second current limiting transistor after the initial duration.