pth03010 Astec Powe, pth03010 Datasheet - Page 12

• Manufacturer Part Number: pth03010
• Description: Pth03020 3.3vin Single
• Manufacturer: Astec Powe

The same circuit also provides a power-down sequence. Power
down is the reverse of power up, and is accomplished by lowering
the track control voltage back to zero volts. The important constraint
is that a valid input voltage must be maintained until the power down
is complete. It also requires that Q1 be turned off relatively slowly.
This is so that the Track control voltage does not fall faster than
Auto-Track's slew rate capability, which is 5 V/ms. The components
R1 and C1 in Figure 15 limit the rate at which Q1 can pull down the
Track control voltage. The values of 100 kΩ and 0.047 µF correlate to
a decay rate of about 0.6 V/ms.
The power-down sequence is initiated with a low-to-high transition at
the On/Off Control input to the circuit. Figure 17 shows the power-
down waveforms. As the Track control voltage falls below the
nominal set-point voltage of each power module, then its output
voltage decays with all the other modules under Auto-Track™
control.
Notes on the of Use Auto-Track™
1 The Track pin voltage must be allowed to rise above the module’s
2 The Auto-Track™ function will track almost any voltage ramp
3 The absolute maximum voltage that may be applied to the Track
4 The module output will not follow the voltage at the Track pin until
5 After the soft-start sequence is complete, the module is capable
Application Note © Artesyn Technologies® 2005
The information and specifications contained in this Application Note are believed to be correct
at time of publication. However, Artesyn Technologies accepts no responsibility for
consequences arising from printing errors or inaccuracies. The information and specifications
contained or described herein are subject to change in any manner at any time without notice.
No rights under any patent accompany the sale of any such product(s) or information
contained herein.
1 1 2 2
set-point voltage before the module can regulate at its adjusted
set-point voltage.
during power up, and is compatible with ramp speeds of up to 1
V/ms.
pin is V
the module has completed its soft-start cycle. The soft start-cycle
takes up to about 20 ms to complete. During this time it is
recommended that the Track pin be held at ground potential.
of both sinking and sourcing current when following the voltage at
the Track pin.
On/Off Control
1 = Power Down
0 = Power Up
+5V
0V
Figure 15 - Sequenced Power Up and Power Down
R1
100k
in
.
0.047µF
Q
BSS138
1
C
1
Using Auto-Track™
C
C
in
in
+
+
U1
U2
File Name: an_pth03020.pdf Rev (05): 21 Dec 2005
2
2
V
Inhibit
V
Inhibit
in
in
10
10
3
3
9
1
9
1
PTH05020W
GND
PTH05010W
GND
Track
Track
8
8
7
7
4k12
698
R2
R
3
5
V
4
5
V
4
o
o
6
6
C
C
out
out
+
+
V
o1
V
o2
= 3.3V
= 2V
HORIZ SCALE: 10 ms/Div
The pre-bias start-up feature is not compatible with Auto-Track™.
This is because when the module is under Auto-Track™ control, it
is fully active and will sink current if the output voltage is below
that of a back-feeding source. Therefore to ensure a pre-bias hold-
off, one of the following two techniques must be followed when
input power is first applied to the module. The Auto-Track™ func-
tion must either be disabled, or the module’s output held off using
the Inhibit pin.
The Auto-Track
ately applying a voltage to the module’s Track pin that is greater
than its set-point voltage. This can be easily accomplished by
pulling the Track pin up to Vin through a 1 kΩ resistor.
HORIZ SCALE: 10 ms/Div
Figure 17 - Power Down with Auto-Track Control
Figure 16 - Power Up with Auto-Track Control
PTH03020 Single Series | Application Note 151
™
function can be disabled at power up by immedi-
ON/OFF input
(5 V/Div)
Vo2 (1 V/Div)
Vo1 (1 V/Div)
Vo2 (1 V/Div)
ON/OFF input
(5 V/Div)
Vo1 (1 V/Div)