Application Note 1903
2
AN1903.1
March 11, 2014
Typical Start-up Waveforms
Output Voltage Programming
The ISL91108IIA-EVZ evaluation board uses resistors to program
the output voltage. To change the output voltage, resistor R1
should be removed and replaced with a resistor value
corresponding to the desired output voltage, as shown in Table 4.
A precision resistor with 1% tolerance should be used.
FIGURE 1. ISL91108 START-UP WITH V
IN
= 2V and V
OUT
= 3.3V
LX1
2V/DIV
2V/DIV
LX2
2V/DIV
V
OUT
2V/DIV
EN
V
IN
= 2V
V
OUT
= 3.3V
400µs/DIV
I
OUT
= 200mA
FIGURE 2. ISL91108 START-UP WITH V
IN
= 4V and V
OUT
= 3.3V
LX1
2V/DIV
2V/DIV
LX2
2V/DIV
V
OUT
2V/DIV
EN
V
IN
= 4V
V
OUT
= 3.3V
400µs/DIV
I
OUT
= 200mA
TABLE 4. OUTPUT VOLTAGE PROGRAMMING
DESIRED OUTPUT VOLTAGE
(V)
R1 RESISTOR VALUE
(k
Ω
)
2.0
90.9
2.5
127
3.0
165
3.3
187
3.6
210
4.0
243
4.5
280
5.0
316
