PT6715_14 Datasheet, PDF (5/9 Pages) Texas Instruments – 13-A Output Current

Application Notes
PT6705/PT6715 Series
Adjusting the Output Voltage of the PT6705 and
PT6715 Excalibur™ Series of Regulators
Both the PT6705 and PT6715 series ISRs are non-
programmable versions of the PT6700 Excalibur™
family of converters. The output voltage of these regula-
tors have a fixed output voltage, which may be adjusted
higher or lower than the factory pre-set voltage using a
single external resistor. Table 2-1 gives the adjustment
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 2-1 and Table 2-2 for both the placement and
value of the required resistor, either (R₁) or R₂ as appropriate.
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.
Correspondingly the resistors (R₁) and R₂ may be then be
connected from V_o Adjust to either V_out or GND
respectively.
4. The PT6705 series requires a 12V external bias voltage in
order to operate (see data sheet). An external bias voltage is
not required for the PT6715 series.
5. Adjusting the output voltage of the PT6705 and PT6715
(3.3V output) higher than the factory pre-set voltage may
require an increase in the minimum input voltage. These
two models must comply with the following requirements
for V_in(min).
PT6705:
V_in(min)
= (V_a + 1)V
PT6715:
V_in(min)
= (V_a + 1)V or 4.5V, whichever is greater.
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 = Reference voltage (Table 2-1)
R_o = Resistance constant (Table 2-1)
R_s = Internal series resistance (Table 2-1)
Figure 2-1
Bias
(Req'd for PT6705)
2
3
Stby*
V
Bias
17
Sns(+)
+5V
4,5,6
V _in
PT6705/PT6715 V _out ^13–16
+
C _in
GND
8–12
Vo(adj) Sns(-)
1
7
(R1)
Adj Down
R2
Adjust Up
+
C _out
Vo
L
O
A
D
COM
COM
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