MIC24045 Evaluation Board User’s Guide
DS50002619A-page 10
2017 Microchip Technology Inc.
5. Turn on the power supply.
6. To modify the Current Limit, Switching Frequency, Output Voltage, Soft Start time
and other features of the part, use the I
2
C Monitor Graphical User Interface (for
more details, see
Chapter 3. “GUI Installation and Operation”
and
Chapter
4. “GUI Description”
).
7. Using the
Enable
button in the GUI, turn on the converter.
8. Once
Enable
is turned on, the voltage set using the GUI should be present at the
output of the converter.
2.3
ON-BOARD LOAD TRANSIENT GENERATOR
The MIC24045 Evaluation Board provides circuitry to enable load transient testing with
fast current rise time and fast yet controlled fall time. This is done by a fast turn-on,
controlled turn-off MOSFET switch (Q1). Resistive loads (R8 to R11) can be selectively
connected by means of header J10. MOSFET Q1 must be driven by an external signal
generator, connected at J15, using a square wave (suggested low level = 0V, high
level = 5V-6V). Drive levels can be adjusted to modify the switching speed of Q1, but
should always ensure complete turn-on and turn-off of Q1 after settling, while not
exceeding its V
GS
ratings. It is very important not to exceed the power dissipation limit
of R8 to R11. Using 2512 resistors (1W rating), the constraint is as shown in
Equation 2-1
(R
LOAD
takes the values of R8 to R11):
EQUATION 2-1:
The on-board load transient generator is especially useful when testing at very low
output voltages, since not many active loads can perform well under those conditions,
while current rise times, achievable with external load boards, are limited by stray
inductance.
2.4
LOOP GAIN MEASUREMENT
The MIC24045 Evaluation Board provides injection points and a termination resistor for
AC loop gain measurements. Inject the oscillator at J2 through the insulation
transformer and connect the A (CH1) and B (CH2) channels at J4 and J5, respectively,
or as indicated by the operating instructions of the particular loop gain analyzer in use.
D
V
OUT
2
R
LOAD
-----------------
1W
Where:
D
= on time duty cycle of Q1
V
OUT
= selected output voltage
R
LOAD
= the value of resistors R8 to R11 (default board value is 1
)
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