Datasheet

Application Notes
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PTH Series of Wide-Output Adjust
Power Modules (3.3/5-V Input)
Margin Up/Down Controls
The PTHxx060W, PTHxx010W, PTHxx020W, and
PTHxx030W products incorporate Margin Up and Margin
Down control inputs. These controls allow the output
voltage to be momentarily adjusted
1
, either up or down,
by a nominal 5 %. This provides a convenient method
for dynamically testing the operation of the load circuit
over its supply margin or range. It can also be used to verify
the function of supply voltage supervisors. The ±5 %
change is applied to the adjusted output voltage, as set by
the external resistor, R
set
at the V
o
Adjust pin.
The 5 % adjustment is made by pulling the appropriate
margin control input directly to the GND terminal
2
.
A low-leakage open-drain device, such as an n-channel
MOSFET or p-channel JFET is recommended for this
purpose
3
. Adjustments of less than 5 % can also be accom-
modated by adding series resistors to the control inputs.
The value of the resistor can be selected from Table 3-2,
or calculated using the following formula.
Up/Down Adjust Resistance Calculation
To reduce the margin adjustment to something less than
5 %, series resistors are required (See R
D
and R
U
in
Figure 3-8). For the same amount of adjustment, the
resistor value calculated for R
U
and R
D
will be the same.
The formulas is as follows.
R
U
or R
D
=
499
– 99.8 kΩ
∆%
Where ∆% = The desired amount of margin adjust in
percent.
Notes:
1. The Margin Up* and Margin Dn* controls were not
intended to be activated simultaneously. If they are
their affects on the output voltage may not completely
cancel, resulting in the possibility of a slightly higher
error in the output voltage set point.
2. The ground reference should be a direct connection to
the module GND at pin 7 (pin 1 for the PTHxx050).
This will produce a more accurate adjustment at the
load circuit terminals. The transistors Q
1
and Q
2
should
be located close to the regulator.
3. The Margin Up and Margin Dn control inputs are not
compatible with devices that source voltage. This includes
TTL logic. These are analog inputs and should only be
controlled with a true open-drain device (preferably
a discrete MOSFET transistor). The device selected
should have low off-state leakage current. Each input
sources 8 µA when grounded, and has an open-circuit
voltage of 0.8 V.
Figure 3–8; Margin Up/Down Application Schematic
Table 3-2; Margin Up/Down Resistor Values
% Adjust R
U
/ R
D
5 0.0 kΩ
4 24.9 kΩ
3 66.5 kΩ
2 150.0 kΩ
1 397.0 kΩ
C
out
+
C
in
V
IN
GND
MargDn
L
O
A
D
Q
2
+V
OUT
Q
1
+
MargUp
0V
+V
o
R
D
R
U
PTH05010W
(
Top View
)
1
2
10 9 8
7
6
543
GND
R
SET
0.1 W, 1 %