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, Rset at the Vo 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 RD and RU in

Figure 3-8). For the same amount of adjustment, the

resistor value calculated for RU and RD will be the same.

The formulas is as follows.

R

U or RD =

499

– 99.8

k

Ω

∆%

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 Q1 and Q2 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

RU / RD

5

0.0 k

Ω

4

24.9 k

Ω

3

66.5 k

Ω

2

150.0 k

Ω

1

397.0 k

Ω

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

5

4

3

GND

R

SET

0.1 W, 1 %