=

´

OUT

ON

IN

SW

V

1

t

V

f

+

+

–

PWM

Comparator

Driver

ESR

UDG-11168

8 kW

+

–

+

VREF

+

TPS53317

www.ti.com

SLUSAK4

– JUNE 2011

PWM Frequency and Adaptive on Time Control

In general, the on-time (at the SW node) can be estimated by Equation 1.

where

•

(1)

The on-time pulse is sent to the top FET. The inductor current and the current feedback rises to peak value.

Each ON pulse is latched to prevent double pulsing. Switching frequency settings are shown in .

Non-Droop Configuration

The TPS53317 can be configured as a non-droop solution. The benefit of a non-droop approach is that load

regulation is flat, therefore, in a system where tight DC tolerance is desired, the non-droop approach is

recommended. For the Intel system agent application, non-droop is recommended as the standard configuration.

The non-droop approach can be implemented by connecting a resistor and a capacitor between the COMP and

the VREF pins. The purpose of the type II compensation is to obtain high DC feedback gain while minimizing the

phase delay at unity gain cross over frequency of the converter.

that calculates these values is available from your local TI Field Application Engineer.

Figure 4 shows the basic implementation of the non-droop mode using the TPS53317.

Figure 4. Non-Droop Mode Basic Implementation

Copyright

© 2011, Texas Instruments Incorporated

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