Datasheet
Smart Sync Considerations
0.7 1.3 2.1 2.51.7 2.31.91.50.9 1.1
5
6
8
9
11
12
14
15
13
10
7
V
I
– Input Voltage – V
V
O
– Output Voltage – V
Meets V
O
Ripple
Specification
Increased V
O
Ripple
f
SW
= 300 kHz
0.7 1.3 2.1 2.51.7 2.31.91.50.9 1.1
5
6
8
9
11
12
14
15
13
10
7
V
I
– Input Voltage – V
V
O
– Output Voltage – V
f
SW
= 400 kHz
f
SW
= 350 kHz
f
SW
= 300 kHz
f
SW
= 240 kHz
Auto-Track™ Function
How Auto-Track™ Works
PTH08T220W , PTH08T221W
www.ti.com
................................................................................................................................................... SLTS252K – NOVEMBER 2005 – REVISED JUNE 2009
Operating the PTH08T220W with a low duty cycle may increase the output voltage ripple due to pulse skipping
of the PWM controller. When operating at the nominal switching frequency, input voltages greater than (V
O
× 11)
may cause the output voltage ripple to increase (typically 2 × ).
Synchronizing to a higher frequency and operating with a low duty cycle may impact output voltage ripple. When
operating at 300 kHz, Figure 27 shows the operating region where the output voltage ripple meets the electrical
specifications and the operating region where the output voltage ripple may increase. Figure 28 shows the
operating regions for several switching frequencies. For example, a module operating at 400 kHz and an output
voltage of 1.2 V, the maximum input voltage that meets the output voltage ripple specification is 10 V. Exceeding
10 V may cause in an increase in output voltage ripple. As shown in Figure 28 , operating below 6V allows
operation down to the minimum output voltage over the entire synchronization frequency range without affecting
the output voltage ripple. See the Electrical Characteristics table for the synchronization frequency range limits.
Figure 27. V
O
Ripple Regions at 300 kHz
(1) (2)
Figure 28. V
O
Ripple Regions
(1) (2)
(1) When operating at the nominal switching frequency refer to the 300 kHz plot.
(2) Operation above a given curve may cause the output voltage ripple to increase (typically 2 × ).
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.
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
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