Datasheet

www.ti.com

APPLICATION INFORMATION

Introduction

Programming Operating Frequency

* 3.98 10

)

5.14 10

* 8.6 (kW)

(1)

TPS40100

SLUS601–MAY 2005

The TPS40100 is a synchronous buck controller targeted at applications that require sequencing and output

voltage margining features. This controller uses a current feedback mechanism to make loop compensation

easier for loads that can have wide capacitance variations. Current sensing (for both current feedback and

overcurrent) is true differential and can be done using the inductor DC resistance (with a R-C filter) or with a

separate sense resistor in series with the inductor. The overcurrent level is programmable independently from

the amount of current feedback providing greater application flexibility. Likewise, the overcurrent function has

user programmable integration to eliminate nuisance tripping and allow the user to tailor the response to

application requirements. The controller provides an integrated method to margin the output voltage to ± 3% and

± 5% of its nominal value by simply grounding one of two pins directly or through a resistance. Powergood and

clock synchronization functions are provided on dedicated pins. Users can program operating frequency and the

closed loop soft-start time by means of a resistor and capacitor to ground respectively. Output se-

quencing/tracking can be accomplished in one of three ways: sequential (one output comes up, then a second

comes up), ratiometric (one or more outputs reach regulation at the same time – the voltages all follow a

constant ration while starting) and simultaneous (one or more outputs track together on startup and reach

regulation in order from lowest to highest).

Operating frequency is set by connecting a resistor to GND from the RT pin. The relationship is:

where

• f

is the switching frequency in kHz

• R

is in kΩ

Figure 1 and Figure 2 show the relationship between the switching frequency and the R

resistor as described in

Equation 1. The scaling is different between them to allow the user a more accurate views at both high and low

frequency.