SLTS102A Datasheet, PDF (6/8 Pages) Texas Instruments – 14-A 12V-Input Adjustable Integrated Switching Regulator

Application Notes
PT6725 Series
Adjusting the Output Voltage of the PT6725
Series of Integrated Switching Regulators
The PT6725 series of ISRs are non-programmable
versions of the PT6721/2 Excalibur™ regulators. The
regulators have a fixed output voltage, which may be
adjusted higher or lower than the factory pre-set voltage
using a single external resistor. Table 1 gives the adjust-
ment range for each model in the series as V_a (min) and
V_a (max).
Adjust Up: An increase in the output voltage is obtained by
adding a resistor R₂, between pin 1 (V_o Adjust) and pin 7
(Remote Sense GND).
Adjust Down: Add a resistor (R₁), between pin 1 (V_o Adjust)
and pin 17 (Remote Sense V_out).
Refer to Figure 1 and Table 2 for both the placement and value
of the required resistor, either (R₁) or R₂ as appropriate.
The values of (R₁) [adjust down], and R₂ [adjust up], can
also be calculated using the following formulas.
(R₁)
=
R_o ( V_a –V_r )
V_o – V_a
– R_s
kΩ
R₂
=
R_o ·V_r
V_a – V_o
– R_s
kΩ
Where: V_o = Original output voltage
V_a = Adjusted output voltage
V_r = The reference voltage (Table 1)
R_o = The multiplier resistance (Table 1)
R_s = The internal series resistance (Table 1)
Figure 1
+5V
4,5,6
2
Stby*
V_in
17
Sns(+)
PT6725
V_out ^13–16
+
C_in
GND
Vo(adj) Sns(-)
8–12 1
7
(R1)
Adj Down
R2
Adjust Up
+
C_out
Vo
L
O
A
D
COM
COM
Notes:
1. Use only a single 1% resistor in either the (R₁) or R₂
location. Place the resistor as close to the regulator as
possible.
2. Never connect capacitors from V_o Adjust to either GND,
V_out, or the Remote Sense pins. Adding capacitance to the
V_o Adjust pin will affect the stability of the ISR.
3. If the Remote Sense feature is not being used, pin 7 must
be connected to pin 8 for optimum output voltage
accuracy. The resistors (R₁) and R₂ may then be connected
from ‘V_o Adjust’ to either V_out or GND respectively.
For technical support and more information, see inside back cover or visit www.ti.com