Time (ms)

Current

Feedback

t

ON

t

V

CS

V

COMP

UDG-10187

V

REF

TPS51463

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SLUSAX2 – FEBRUARY 2012

APPLICATION INFORMATION

Functional Overview

The TPS51463 is a D-CAP+™ mode adaptive on-time converter. The output voltage is set using a 2-bit DAC that

outputs a reference voltage in accordance with the code defined in Table 1. VID-on-the-fly transitions are

supported with the slew rate controlled by a single capacitor on the SLEW pin. The converter automatically runs

in discontinuous conduction mode (DCM) to optimize light-load efficiency. Two switching frequency selections

are provided, (700 kHz and 1 MHz) to enable optimization of the power chain for the cost, size and efficiency

requirements of the design.

In adaptive on-time converters, the controller varies the on-time as a function of input and output voltage to

maintain a nearly constant frequency during steady-state conditions. In conventional constant on-time converters,

each cycle begins when the output voltage crosses to a fixed reference level. However, in the TPS51463, the

cycle begins when the current feedback reaches an error voltage level which is the amplified difference between

the reference voltage and the feedback voltage.

PWM Operation

Referring to Figure 2, in steady state, continuous conduction mode, the converter operates in the following way.

senses where the two waveforms cross and triggers the on-time generator.

Figure 2. D-CAP+™ Mode Basic Waveforms

The current feedback is an amplified and filtered version of the voltage between PGND and SW during low-side

system accuracy and reduce the dependence of circuit performance on layout.

Copyright © 2012, Texas Instruments Incorporated

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