MCP16301 300 mA D
2
PAK Demo Board User’s Guide
DS51983A-page 12 © 2011 Microchip Technology Inc.
2.2 GETTING STARTED
The MCP16301 300 mA D
2
PAK Demo Board is fully assembled and tested to evaluate
and demonstrate the MCP16301 capability.
2.2.1 Power Input and Output Connection
2.2.1.1 POWERING THE MCP16301 300 MA D
2
PAK DEMO BOARD
The MCP16301 300 mA D
2
PAK Demo Board is fully assembled, tested and ready for
evaluation. Apply positive input voltage to the V
IN
terminal and the corresponding
return to the GND terminal. The maximum input voltage should not exceed 26V. An
electronic load or resistive load can be used for evaluation or the intended system load
can be connected. The electronic loads attempt to sink current at 0V during startup. A
resistive load or constant resistance is recommended for startup evaluation. Connect
the positive voltage terminal of the load to the V
OUT
terminal on the demo board, and
connect the negative or return side of the load to the GND terminal.
2.2.1.2 BOARD TESTING
To test the board, follow the next steps:
1. Apply the input voltage.
2. An internal pull up resistor is connected from V
IN
to the EN input of the
MCP16301. Once the input voltage is greater than 3.5V, the device begins to
switch. Apply greater than 4V supply to the input for proper operation. A minimum
load is required to regulate the output to 3.3V. For minimum load requirements
(light load conditions), detailed information is provided in the data sheet.
3. The measured output voltage should be 3.3V typical. Adjusting the input voltage
and load should not cause the output to vary more than a few mV over the oper-
ating range of the converter.
2.2.2 How the MCP16301 300 mA D
2
PAK Demo Board Boost Strap
Operates
The MCP16301 integrates a low resistance N-Channel MOSFET. A high side or
floating supply is needed to drive the gate of the N-Channel MOSFET above the input
voltage to turn it on. The demo board uses the output voltage (3.3V) to charge the boost
cap, while inductor current flows, clamping the SW node to a diode drop below ground.
Prior to start up, there is no inductor current, so an internal pre-charge circuit charges
the boost cap up to a minimum threshold. Once charged, the N-Channel can be turned
on, ramping current into the inductor.
The worst case operating conditions for charging the boost capacitor occur at minimum
V
IN
and no load. At minimum V
IN
(4V), there is not enough head room to pre-charge
the boost cap to a high value. At no load, the converter is operating at a minimum or
very low duty cycle, putting a small amount of current into the inductor. When the switch
turns off the inductor, current decays very quickly, resulting in a small time to recharge
the boost capacitor.
