Texas Instruments TPS54240EVM-VSON, User Manual, Page: 19 / 25

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Modifications
19 SNVU602 – May 2019
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TPS54240EVM-VSON Regulator Evaluation Module
5 Modifications
These evaluation modules are designed to provide access to the features of the TPS54240. Some
modifications can be made to this module.
5.1 Output Voltage Setpoint
The voltage divider of R
3
and R
6
is used to set the output voltage of the EVM. The 51-
Ω
resistor R
2
is
provided as an aid to check the loop response of the circuit. To change the output voltage of the EVM, it is
necessary to change the value of resistor R
3
. Changing the value of R
3
can change the output voltage
above 0.8 V or 90% V
IN
. The value of R
3
for a specific output voltage can be calculated using Equation 1 .
(1)
Table 5 lists the R
3
values for some common output voltages. Note that V
IN
must be in a range so that the
minimum on-time is greater than 130 ns, and the maximum duty cycle is less than 90%. Higher duty
cycles are possible, but may result in uneven switching behavior. The values given in
Table 5 are
standard values, not the exact value calculated using Equation 1 .
Table 5. Output Voltages Available
OUTPUT
VOLTAGE
(V)
R
3
VALUE
(k Ω )
1.8 12.4
2.5 21.5
3.3 31.6
5 52.3
Be aware that changing the output voltage can affect the loop response. It may be necessary to modify
the compensation components. Also, changing output voltage may need to change L
OUT
and C
OUT
as well.
Check C
OUT
voltage rating if higher V
OUT
is used. See the device data sheet for details.
5.2 Operating Frequency, Soft Start, and UVLO
The operating frequency, soft-start time, and UVLO voltage may also be adjusted. R
5
sets the operating
frequency, C
11
sets the soft-start time and the resistor divider of R
1
and R
2
sets the UVLO start and stop
voltages. See the TPS54240 device data sheet for details on adjusting these parameters.