TPS43000

SLUS489 − OCTOBER 2001

9

www.ti.com

APPLICATION INFORMATION

general information

The TPS43000 is a high-frequency, synchronous PWM controller optimized for distributed power, or

battery-powered applications where size and efficiency are of critical importance. It includes high-speed,

block diagram).

optimizing efficiency

The TPS43000 optimizes efficiency and extends battery life with its low quiescent current and its synchronous

rectifier topology. The additional features of low-power (LP) mode and PFM mode maintain high efficiency over

a wide range of load current.

modes of operation

The TPS43000 has four distinct modes of operation:

The device mode is controlled by the CCM and PFM pins. The CCM pin lets the user decide whether to allow

DCM by connecting the pin to ground or to force CCM by connecting the pin to VIN. The PFM pin lets the user

decide whether to allow automatic PFM by connecting the pin to ground or to force fixed PWM by connecting

the pin to VIN.

fixed PWM with DCM possible (PFM tied to VIN; CCM tied to ground)

In this mode, the device behaves like a standard switching regulator with the addition of a synchronous rectifier.

Shortly after the energizing MOSFET turns off, the synchronous rectifier turns on. The synchronous rectifier

turns off either when the inductor current goes discontinuous (DCM) or just prior to the start of the next clock

cycle (CCM) when the energizing MOSFET turns on. During the small time interval when neither the energizing

MOSFET nor the synchronous rectifier are turned on, the synchronous rectifier MOSFET body diode (or an

optional small external Schottky diode in parallel) carries the current to the output until it goes discontinuous.

The efficiency drops off at light loads as the losses become a larger percentage of the delivered load.