Datasheet

V
I
GND GND
V
O
R
SET
0.05W
1%
PTH08080W
2
4
31
5
V Adj
O
GNDInhibit
V
I
V
O
C
I
C
O
D1(SeeNote3)
R =10k x
SET
W
0.891 V
V -0.9V
out
-1.82kW
PTH08080W
www.ti.com SLTS235D –FEBRUARY 2005–REVISED SEPTEMBER 2013
APPLICATION INFORMATION
Adjusting the Output Voltage of the PTH08080W Wide-Output Adjust Power Modules
The V
O
Adjust control (pin 4) sets the output voltage of the PTH08080W product. The adjustment range is from
0.9 V to 5.5 V. The adjustment method requires the addition of a single external resistor, R
SET
, that must be
connected directly between the V
O
Adjust and GND (pin 2). Table 1 gives the standard external resistor for a
number of common bus voltages, along with the actual voltage the resistance produces.
For other output voltages, the value of the required resistor can either be calculated using the following formula,
or simply selected from the range of values given in Table 2. Figure 10 shows the placement of the required
resistor.
Table 1. Standard Values of R
SET
for Common Output
Voltages
V
O
R
set
V
O
(Required) (Standard Value) (Actual)
5 V
(1)
348 Ω 5.010 V
3.3 V 1.87 kΩ 3.315 V
2.5 V 3.74 kΩ 2.503 V
2 V 6.19 kΩ 2.012 V
1.8 V 8.06 kΩ 1.802 V
1.5 V
(2)
13.0 kΩ 1.501 V
1.2 V
(2)
27.4 kΩ 1.205 V
1 V
(2)
86.6 kΩ 1.001 V
0.9 V
(2)
Open 0.9 V
(1) The minimum input voltage is 4.5 V or (V
O
+ 1.1) V, whichever is
greater.
(2) The maximum input voltage is 18 V or (V
O
× 10) V, whichever is
lesser.
(1) A 0.05-W rated resistor may be used. The tolerance should be 1%, with a temperature stability of 100 ppm/°C (or
better). Place the resistor as close to the regulator as possible. Connect the resistor directly between pins 4 and 2
using dedicated PCB traces.
(2) Never connect capacitors from V
O
Adjust to either GND or V
O
. Any capacitance added to the V
O
Adjust pin affects
the stability of the regulator.
(3) The protection diode, D1, is required whenever the output voltage setpoint is adjusted to 5.25 V (or higher) and V
I
is
16 V or greater.
Figure 10. V
O
Adjust Resistor Placement
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