teristic. The ripple rejection is externally adjustable

SVR (jw) =

=

10

–6

1+

gm

R1

(1 +

)

Where:

gm = 2 . 10

value on linear region

R1

= fixed ratio

R2

µF

The reaction time of the supervisor loop is given by

the value of the ripple voltage is so high and its nega-

tive peak is fast/enough to determine an istantane-

ous decrease of the dropout till 1.2V, the OTA works

in a higher transconductancecondition [range (3) of

the characteristic] and discharge the capacitor rapi-

dously.

If the ripple frequency is high enough the capacitor

won’t charge itself completely, and the output vol-

tage reaches a small value allowing a better ripple

rejection; the device’s again working as a filter (fast

transient range).

µF ; f =100 Hz aSVR of35 is obtained.

Figure 2 : Nonliner Transfer Characteristic of the

Drop Control Unit.

Figure 3 : Supply Voltage Rejection vs. Fre-

1) Nor mal operati ng range ( high ri ppl e rej ect io n)

2) Drop controlled range (medium rippl e rejection)

Figure 4 : Supply voltage Rejection vs. Input Volt-

age.

Figure 5 : Output Voltage vs. Input Voltage.

L4918

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