Datasheet

Output Voltages Greater Than V
REF
1-3
Introduction
1.2 Output Voltages Greater Than V
REF
For applications requiring an output voltage greater than the internal reference
voltage (V
FB
) of 1.224 V, a standard linear regulator circuit with an external
voltage divider is all that is necessary. The lower section of Figure 1 shows a
generic linear regulator circuit with an input capacitor (C1), output capacitor
(C3), external voltage divider (R3/R4), and the enable circuit with either a
pullup resistor (R1) or pulldown resistor (R2) as required. None of the backside
components are required for this application. If a delayed enabled is desired,
the R1 and R2/C2 component pads can be used for an RC circuit. When using
the TPS76918EVM–127 or the TPS76933EVM–127, the external divider is
not required and R3 is a 0-Ω resistor used to connect the sense terminal to V
O
.
When using the TPS76901EVM–127 (adjustable output voltage), it is recom-
mended that the divider current (I
REF
) be set to 7 µA. Choosing R4 to be
169 kΩ and calculating R3 for V
O
accomplishes this.
R3
V
O
V
FB
1 R4
(1)
Where:
V
FB
= 1.224 V
R4 = 169 kΩ
Then
R3
138.07 V
O
169 kΩ
Lower value resistors can be used but are not as power efficient. Higher value
resistors should be avoided due to leakage currents at FB increasing the out-
put voltage error. Table 1–1 shows various voltage options and the suggested
resistor values.
Table 1–1.Resistor Values
OUTPUT VOLTAGE
(V)
DIVIDER RESISTANCE
(kΩ)
(V)
R3 R4
2.5 174 169
3.3 287 169
3.6 324 169
4.0 383 169
5.0 523 169