Installation and Operation
2019 Microchip Technology Inc.
DS50002914A-page 15
2.3.1.5
I
2
C PULL-UP VOLTAGE SELECTION
The MIC33M656 Evaluation Board is equipped with a jumper for selecting the I
2
C
pull-up supply voltage. The J8 header can be used to select the I
2
C pull-up voltage to
either V
USB
or V
IN
. If a different pull-up voltage is desired, it can be injected into the
PWR pin of J2. In this case, make sure that no jumper is installed on header J8 to
prevent shorting of the externally injected pull-up voltage to either V
USB
or V
IN
.
2.3.1.6
USING THE MIC33M656 EVALUATION BOARD WITH THE EXTERNAL
I
2
C MASTER
In order to use the MIC33M656 with an external I
2
C master (such as a microcontroller,
microprocessor or another I
2
C master), the on-board MCP2221 must be disabled. To
accomplish this, the pull-down resistor R10 must be populated to avoid any
interference between the MCP2221 and the external I
2
C master. If the MCP2221 is not
powered (e.g., by disconnecting the USB cable), then R8 and R11 must also be
removed. Then, the desired I
2
C master can be connected to J2. If the external I
2
C
master already provides pull-up resistors for the SDA and SCL lines, then the I
2
C
pull-up resistors, R6 and R9, present on the MIC33M656 Evaluation Board, are not
needed and must be removed to prevent pull-up voltage conflicts.
2.3.1.7
STARTING THE MIC33M656 WITH A CUSTOM OUTPUT VOLTAGE
To power up the MIC33M656 with a custom output voltage, the MIC33M656 Evaluation
Board must be first powered up with the MIC33M656 disabled (either by placing the EN
jumper on the J6 header in the SDN position, or applying a logic ‘
0
’ voltage on the EN
test point). Program the module via the I
2
C interface (using the PC GUI interface) to
the desired output voltage and then start it by placing the EN jumper on J6, EN position
(or by applying a logic ‘
1
’ voltage on the EN test point). The MIC33M656 does not retain
the set voltage and returns to the default configuration after a power cycle.
2.3.1.8
MIC33M656 EVALUATION BOARD ENABLE OPTIONS
In order to enable the MIC33M656 on the Evaluation Board, three options are provided:
1. The EN jumper placed on the J6 header – By placing a jumper on the EN
position, as described by the silkscreen, and by having EN_INT (bit 1) of the
CTRL1 register (address 0x00) set to ‘
1
’, the MIC33M656 is enabled. By placing
a jumper on the SDN position, the MIC33M656 is disabled. The MIC33M656
Evaluation Board features a pull-down resistor R3 connected to the EN pin, so
by default, without any jumper connected, the regulator will be disabled.
2. Software controlled – By clearing EN_INT (bit 1) of the CTRL1 register
(address 0x00), the MIC33M656 status is controlled by EN_CON (bit 0) of the
CTRL1 register and the EN pin status is ignored. By setting the EN_CON bit, the
MIC33M656 is enabled and by clearing the EN_CON bit, the MIC33M656 is
disabled.
3. MCP2221 GPIO control – By checking “Enable GP0 Control” in the I2CMonitor
GUI, the EN pin is controlled by the GP0 output of the MCP2221, and by using
the
GP0
active
button, the MIC33M656 is enabled or disabled.
Note:
When using MCP2221 GPIO control, remove any low-impedance connec-
tion between the EN pin and V
IN
or GND (e.g., a jumper on the J6 header)
as this may cause undefined behavior.
