2 Operation
Once the above connections are made and the appropriate jumpers are set, the EVM is ready to use.
The EVM is configured for a 5-V output. The output voltage can be changed by changing the values of
resistors R2 (R
FBT
) and or R3 (R
FBB
). Depending on the output capacitors and the desired loop performance, a
feed-forward capacitor, C5 (C
FF
) can be desirable. A space is available on the EVM for this optional component.
See the
LM636x5-Q1 3.5-V to 36-V, 1.5-A, and 2.5-A Automotive Step-down Voltage Converter Data Sheet
for
more information.
The switching mode of the EVM can be changed by using the MODE jumper; this selection can be made
on-the-fly
.
The RESET flag is used to indicate when the output voltage is /- 5 % of the regulated value. This EVM is
configured with a 100 kΩ pull-up resistor from RESET to VCC (about 5V). A low on RESET indicates the output
voltage is out of regulation. The pull-up resistor can be removed and the open-drain RESET pin can be used to
control a system processor from the EVM. Be sure to limit the voltage on the RESET to less than the specified
Abs max for this pin.
Some components in the EMI filter are not populated. The user is free to experiment with different EMI filter
components as desired.
Loop gain measurements (Bode plots) can be made using the setup shown in
.
The EVM has been designed for maximum flexibility regarding component selection. This allows the user to
place preferred components such as the inductor, the capacitors, or both, on the board and test the performance
of the regulator. This way the power supply system can be tested before committing the design to production.
3 Performance Curves
Curves showing typical performance data are found in
other data, consult the device data sheet.
Output Current (A)
Ef
ficiency (%)
0
0.5
1
1.5
2
2.5
3
60
65
70
75
80
85
90
95
8V
13.5V
18V
24V
Figure 3-1. Efficiency: AUTO Mode, V
OUT
= 5 V, f
SW
= 2100 kHz
Output Current (A)
Output V
oltage (V
)
0
0.5
1
1.5
2
2.5
3
5
5.01
5.02
5.03
5.04
5.05
8V
13.5V
18V
24V
Figure 3-2. Line and Load Regulation: AUTO Mode,
V
OUT
= 5 V, f
SW
= 2100 kHz
Operation
6
LM63635DNEVM EVM User’s Guide
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