Q1VDS (2 V/div)

VO (2 V/div)

II (2 A/div)

t − Time − 40 ms/div

PTH12060W/L

SLTS217H – MAY 2003 – REVISED DECEMBER 2008 .................................................................................................................................................... www.ti.com

Figure 11. Power-Up from Track Control

NOTE:

If a prebias condition is not present, it is highly recommended that the Track control

pin be used for controlled power-up and power-down. If Track control is not used, the

output voltage starts up and overshoots by as much as 10%, before settling at the

output voltage setpoint.

How Auto-Track™ Works

Auto-Track works by forcing the module output voltage to follow a voltage presented at the Track control pin (1).

This control range is limited to between 0 V and the module set-point voltage. Once the track-pin voltage is

raised above the set-point voltage, the module output remains at its set-point (2). As an example, if the Track pin

of a 2.5-V regulator is at 1 V, the regulated output is 1 V. If the voltage at the Track pin rises to 3 V, the regulated

output does not go higher than 2.5 V.

When under Auto-Track control, the regulated output from the module follows the voltage at its Track pin on a

volt-for-volt basis. By connecting the Track pin of a number of these modules together, the output voltages follow

a common signal during power up and power down. The control signal can be an externally generated master

ramp waveform, or the output voltage from another power supply circuit (3). For convenience, the Track input

incorporates an internal RC-charge circuit. This operates off the module input voltage to produce a suitable rising

waveform at power up.

16

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