250

240

300

325

350

0.7

1.1

1.3

1.7

2.1

5

7

9

13

11

15

V

0.9

1.5

1.9

6

8

10

14

12

275

375

400

f

250

275

300

325

350

375

400

240

Auto-Track™ Function

How Auto-Track™ Works

PTH08T240F

To achieve the output voltage ripple specified in the electrical characteristics table, the maximum input voltage

for a given output voltage is limited. The input voltage to output voltage ratio limit is 11 to 1 for the PTH08T240F.

However, when using SmartSync, the maximum allowable input voltage varies as a function of output voltage

and switching frequency. Operationally, the maximum input voltage is inversely proportional to switching

frequency. Synchronizing to a higher frequency causes greater restrictions on the input voltage range. For a

given switching frequency, Figure 30 shows how the recommended maximum input voltage varies with output

voltage.

For example, a module operating at 375 kHz and an output voltage of 0.9 V, the maximum input voltage is 8 V.

Exceeding the maximum input voltage may cause in an increase in output ripple voltage and increased output

voltage variation.

As shown in Figure 30, input voltages below 6 V can operate down to the minimum output voltage over the entire

synchronization frequency range. See the Electrical Characteristics table for the synchronization frequency range

and pulse limits.

RECOMMENDED INPUT VOLTAGE

vs

OUTPUT VOLTAGE

Figure 30.

The Auto-Track function is unique to the PTH/PTV family, and is available with all POLA products. Auto-Track

was designed to simplify the amount of circuitry required to make the output voltage from each module power up

and power down in sequence. The sequencing of two or more supply voltages during power up is a common

requirement for complex mixed-signal applications that use dual-voltage VLSI devices such as the TMS320™

DSP family, microprocessors, and ASICs.

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

of a 1.5-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 1.5 V.

26

Submit Documentation Feedback

Copyright © 2006–2008, Texas Instruments Incorporated

Product Folder Link(s): PTH08T240F