pth12040 Astec Powe, pth12040 Datasheet - Page 9

• Manufacturer Part Number: pth12040
• Description: Pth12040 12vin Single
• Manufacturer: Astec Powe

Notes:
1 Use a resistor with a tolerance of 1% (or better). Place the resistor
2 Never connect capacitors from V
V
a
0.800
0.825
0.850
0.875
0.900
0.925
0.950
0.975
1.000
1.025
1.050
1.075
1.100
1.125
1.150
1.175
1.200
1.225
1.250
1.275
1.300
1.325
1.350
1.375
1.400
1.425
1.450
1.475
as close to the regulator as possible. Connect the resistor directly
between pins 17 and nearest ground pin (16) using dedicated
PCB traces.
Any capacitance added to the V
of the regulator.
1.50
1.55
Req’d
OUTPUT VOLTAGE SET-POINT RESISTOR VALUES
Table 5 - Output Voltage Set-point Resistor Values
78.31kΩ
62.3kΩ
51.6kΩ
44.0kΩ
38.3kΩ
33.9kΩ
30.3kΩ
27.4kΩ
25.0kΩ
22.9kΩ
21.2kΩ
19.6kΩ
18.3kΩ
17.1kΩ
16.1kΩ
15.1kΩ
14.3kΩ
13.5kΩ
12.8kΩ
12.2kΩ
11.6kΩ
11.1kΩ
10.6kΩ
10.2kΩ
9.73kΩ
8.97kΩ
318kΩ
158kΩ
105kΩ
Open
R
set
V
a
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
2.25
2.30
2.35
2.40
2.45
2.50
2.55
2.60
2.65
2.70
2.75
2.80
2.85
2.90
2.95
3.00
3.05
Req’d
File Name: an_pth12040.pdf Rev (02): 21 Dec 2005
o
7.72kΩ
7.19kΩ
6.73kΩ
5.92kΩ
5.58kΩ
5.26kΩ
4.97kΩ
4.46kΩ
4.23kΩ
4.02kΩ
3.82kΩ
3.64kΩ
3.47kΩ
3.15kΩ
3.01kΩ
2.88kΩ
2.75kΩ
2.63kΩ
2.51kΩ
2.41kΩ
2.21kΩ
2.02kΩ
1.94kΩ
1.86kΩ
o
2.11kΩ
8.3kΩ
6.3kΩ
4.7kΩ
3.3kΩ
2.3kΩ
Adjust pin will affect the stability
R
Adjust to either GND or V
set
V
a
3.10
3.15
3.20
3.25
3.30
3.35
3.40
3.50
3.60
3.70
3.80
3.90
4.00
4.10
4.20
4.30
4.40
4.50
4.60
4.70
4.80
4.90
5.00
5.10
5.20
5.30
5.40
5.50
Req’d
1.78kΩ
1.71kΩ
1.64kΩ
1.57kΩ
1.44kΩ
1.38kΩ
1.27kΩ
1.16kΩ
1.06kΩ
1.5kΩ
971Ω
885Ω
804Ω
728Ω
657Ω
590Ω
526Ω
466Ω
409Ω
355Ω
304Ω
255Ω
209Ω
164Ω
122Ω
R
82Ω
43Ω
0Ω
set
out
.
7.2 Adjusting the Under-Voltage Lockout (UVLO)
The PTH12040W power modules incorporate an input under-voltage
lockout (UVLO). The UVLO feature prevents the operation of the
module until there is sufficient input voltage to produce a valid output
voltage. This enables the module to provide a clean, monotonic
power-up for the load circuit, and also limits the magnitude of current
drawn from the regulator’s input source during the power-up
sequence.
The UVLO characteristic is defined by the on-threshold (V
Hysteresis (V
control is overridden, and the module will not produce an output. The
Hysteresis voltage is the difference between the ‘on’ and ‘off’
threshold voltages. It ensures a clean power-up, even when the input
voltage is rising slowly. The Hysteresis prevents start-up oscillations,
which can occur if the input voltage droops slightly when the module
begins drawing current from the input source.
7.2.1 UVLO Adjustment
The UVLO feature of the PTH12040W module allows for limited
adjustment of both the on-threshold and Hysteresis voltages. The
adjustment is made via the ‘UVLO Prog‘ control pin. When the UVLO
Prog pin is left open circuit the on-threshold and Hysteresis voltages
are internally set to their default values. The ‘on’ threshold has a
nominal voltage of 7.5V, and the Hysteresis 1V. This ensures that the
module will produce a regulated output when the minimum input
voltage is applied (see specifications). The combination correlates to
an ‘off’ threshold of approximately 6.5V. The adjustments are limited.
The on-threshold can only be adjusted higher, and the Hysteresis
voltage can only be reduced in magnitude.
The ‘on’ threshold might need to be raised if the module is powered
from a tightly regulated 12V bus. This would prevent it from
operating if the input bus failed to completely rise to its specified
regulation voltage. The Hysteresis shouldn’t be changed unless
absolutely necessary. A generous amount of Hysteresis ensures that
the module exhibits a clean startup. Therefore adjustment of the
Hysteresis should only be considered if there is a system
requirement to specifically set the off-threshold voltage (in addition to
the on-threshold). Depending on the load regulation of the input
source, the Hysteresis should not be adjusted below 0.5V without
careful consideration.
7.2.2 Adjustment Method
The resistors R
of the on-threshold and Hysteresis voltages. R
the UVLO Prog control pin and VI. R
the on-threshold voltage higher. However, to adjust the hysteresis to
a lower value requires both the R
in the circuit.
The recommended adjustment method requires that any change to
the Hysteresis be determined first. If the Hysteresis is changed, then
a value for R
whether a change is required to the value of V
change to V
location. R
calculating the value of R
Application Note 193
www.artesyn.com
HYS
HYS
THD
HYS
should then be assigned an infinite value for
THD
, then a resistor should not be placed in the R
) voltages. Below the ‘on’ threshold, the Inhibit
must also be calculated. This is irrespective of
, and R
THD
HYS
.
(see Figure 8), provide the adjustment
HYS
THD
and R
alone can be used to adjust
THD
THD
THD
resistors to be placed
If there is no
connects between
THD
) and
HYS
9