L6919C

14/32

Integrated Droop Function

The device uses a droop function to satisfy the requirements of high performance microprocessors, reducing

the size and the cost of the output capacitor.

This method "recovers" part of the drop due to the output capacitor ESR in the load transient, introducing a de-

pendence of the output voltage on the load current

As shown in figure 8, the ESR drop is present in any case, but using the droop function the total deviation of the

tional to the output current. Since the device has an average current mode regulation, the information about the

only in this resistor because the compensation network between FB and COMP has always a capacitor in series

(See fig. 9). The voltage regulated is then equal to:

given by:

Figure 8. Output transient response without (a) and with (b) the droop function

Figure 9. Active Droop Function Circuit

The feedback current is equal to 50

threshold, so the maximum output voltage deviation is equal to:

sunk from the FB pin. The device regulates at the voltage programmed by the VID.

V

OUT

VID

R

FB

R

SENSE

Rg

----------------------

I

OUT

⋅⋅

–

=

(a)

(b)

ESR DROP

ESR DROP

COMP

FB

To VOUT