PT652X Datasheet, PDF (5/8 Pages) Texas Instruments – 8-A 5-V/3.3-V Input Adjustable ISR with Short-Circuit protection

Application Notes
PT6520 Series
Adjusting the Output Voltage of the PT6520
Series of Integrated Switching Regulators
The output voltage of the PT6520 series of integrated
switching regulators (ISRs) may be adjusted higher or
lower than the factory trimmed pre-set voltage with the
addition of a single external resistor. ¹ Table 1 gives the
allowable 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 14 (V_o adjust) and
pins 7-10 (GND).
Adjust Down: Add a resistor (R₁), between pin 14 (V_o ad-
just) and pin 1 V_o(sense) ³.
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
1
Vo(sense)
Vin
4,5,6
Vin
PT6520
11,12,13
Vout
+
C _in
STBY
3
GND
Vo(adj)
7,8,9,10 14
(R1)
Adj Down
R2
Adj
Up
COM
+
C _out
Vo
L
O
A
D
COM
Notes:
1. Use only a single 1% resistor in either the (R₁) or R₂
location. Place the resistor as close to the ISR as
possible.
2. Never connect capacitors from V_o adjust to either
GND, V_out, or the Remote Sense pin. Capacitance
added to the V_o adjust pin will affect the stability of
the ISR.
3. If the Remote Sense feature is not being used, the
resistor (R₁) may be connected between pin 14 (V_o
adjust) and pins 11–13 (V_out).
4. Adjusting the output voltage of the PT6523 (2.5V
model) higher than the factory pre-trimmed output
voltage may increase the minimum input voltage
specified for the part. This model must comply with
the following requirements.
PT6523:
V_in(min) = (V_a + 0.5)V or 3.1V, whichever is greater.
Table 1
ADJUSTMENT AND FORMULA PARAMETERS
Series Pt # PT6527
PT6522
PT6526
V_o (nom)
Va (min)
V_a (max)
Vr (V)
R_o (kΩ)
Rs (kΩ)
1.2
1.09
1.52
0.8
10.0
24.9
1.5
1.47
1.73
1.27
10.2
49.9
1.8
1.75
2.05
1.27
10.0
49.9
PT6525
2.1
1.95
2.45
1.27
10.0
33.2
PT6523
2.5
2.25
2.85
1.27
10.0
33.2
PT6521
3.3
2.75
3.75
1.27
10.0
24.9
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