Installation and Operation
2018 Microchip Technology Inc.
DS50002834A-page 15
2.3.1.7
STARTING THE MIC23356 WITH A CUSTOM OUTPUT VOLTAGE
To power-up the MIC23356 with a custom output voltage, the MIC23356 Evaluation
Board must be first powered-up with the MIC23356 disabled (either by placing the EN
jumper on the J6 header, SDN position, or applying a Logic ‘0’ voltage on the EN test
point). Program it via I
2
C interface to the desired output voltage and then start it by plac-
ing the EN jumper on J6, EN position (or by applying a Logic ‘1’ voltage on the EN test
point). The MIC23356 does not retain the set voltage and returns to the default config-
uration after a power cycle.
2.3.1.8
MIC23356 EVALUATION BOARD ENABLE OPTIONS
In order to enable the MIC23356 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 of register CTRL1
(address
0x00
) set to ‘
1
’, the MIC23356 is enabled. By placing a jumper on the
SDN position, the MIC23356 is disabled. The MIC23356 Evaluation Board fea-
tures 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 register CTRL1 (address
0x00
), the MIC23356 status is controlled by EN_CON (bit 0) of the CTRL1 reg-
ister and the EN pin status is ignored. By setting the EN_CON bit, the MIC23356
is enabled and by clearing the EN_CON bit, the MIC23356 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 MIC23356 is enabled or disabled.
2.3.1.9
PCB LAYOUT CONSIDERATIONS
For the best performance with the minimum occupied board space, some proper layout
techniques should be applied. First, the input and output capacitors should be placed
as close to the MIC23356 as possible and on the same layer as the IC. This will ensure
low ripple and lower switching noise. Then, vias must be used under the MIC23356,
from its exposed pad to the GND plane, in order to improve heat dissipation. Lastly, the
switching node (from the SW pin of the MIC23356 to the inductor) should be as small
as possible to decrease EMI emission.
2.3.1.10 BENCH TESTING AT HIGH CURRENTS
When testing the MIC23356 device at high-load currents or when checking the over-
current protection behavior, it may be necessary to remove the series ammeter shown
in
Figure 2-2
or to replace it with a very low-value shunt resistor. This is because the
internal resistance of many Digital Multimeters (DMMs) used for current measurements
is generally too high.
2.3.1.11
THERMAL CONSIDERATIONS
The MIC23356 Junction-to-Ambient Thermal Resistance
JA, as measured on the
Evaluation Board, is approxi45°C/W. Depending on the loading conditions,
ambient temperature, and device settings, the junction temperature might exceed the
rated operating limit of +125°C due to internal power dissipation. Continuous operation
above the maximum operating limits stated in the data sheet should be avoided.
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.
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