Micrel

MICRF009

January 18, 2005

9

M9999-011805

(408) 955-1690

∆t = droop recovery time

∆V = droop voltage

For example, if user desires

∆t = 10ms and chooses a

4.7µF CAGC, then the allowable droop is about 144mV.

Using the same equation with 200nA, the worst-case pin

leakage, and assuming 1µA of capacitor leakage in the

same direction, the maximum allowable

∆t (shutdown time)

is about 0.56s for droop recovery in 10ms.

The ratio of decay-to-attack time-constant is fixed at 1:10

(that is, the attack time constant is 10 times of the decay

time constant). Generally the design value of 1:10 is

adequate for the vast majority of applications. If adjustment

capacitor may vary the ratio. The value of the resistor must

be determined on a case-by-case basis.