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Smart Sync Input Voltage Limits

V -OutputVoltage-V

O

240kHz

400kHz

350kHz

300kHz

0.7

15

0.9

1.1

1.3

1.5

1.7

2.5

1.9

2.1

2.3

5

14

7

6

9

8

11

10

13

12

Auto-Track™ Function

How Auto-Track™ Works

PTH08T260W, PTH08T261W

SLTS272A – DECEMBER 2006 – REVISED MAY 2007

The maximum input voltage allowed for proper synchronization is duty cycle limited. When using Smart Sync,

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 23 shows how the maximum input voltage varies with output voltage.

For example, for a module operating at 400 kHz and an output voltage of 1.2 V, the maximum input voltage is

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

output voltage variation.

As shown in Figure 23, 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 limits.

Figure 23. Input Voltage vs Output Voltage

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 ICs 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 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

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

rising waveform at power up.

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