SWITCHING FREQUENCY

vs

TIMING RESISTANCE

0

10000

100

50

100

150

200

250

300

R

2500 N

PH

V

DROOP

I

OUT

R

CS

V

REF

V

OUT

+

2500 N

PH

V

DROOP

V

R2

R1 ) R2

TPS40090-Q1

www.ti.com

SLUS845C

– JUNE 2008 – REVISED MAY 2011

The switching frequency of the controller can be synchronized to an external clock applied to the EN/SYNC pin.

The external frequency should be somewhat higher than the free-running clock frequency for synchronization to

take place.

Figure 3.

Setting the Output Voltage Droop

In many applications, the output voltage of the converter is intentionally allowed to droop as load current

increases. This approach (sometimes referred to as active load line programming) allows for better use of the

regulation window and reduces the amount of the output capacitors required to handle the same load current

step. A resistor from the REF pin to the DROOP pin sets the desired value of the output voltage droop.

where:

(9)

•

•

•

•

2500

•

(1)

saturates to approximately 50

Copyright

© 2008–2011, Texas Instruments Incorporated

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