MCP16301 600 mA Demo Board User’s Guide
DS51978A-page 12 2011 Microchip Technology Inc.
2.2 GETTING STARTED
The MCP16301 600 mA Demo Board is fully assembled and tested to evaluate and
demonstrate the MCP16301.
2.2.1 Power Input and Output Connection
2.2.1.1 POWERING THE MCP16301 600 mA DEMO BOARD
The MCP16301 600 mA Demo Board is fully assembled, tested and ready to begin
evaluation. Apply positive input voltage to the V
IN
terminal and its return to the GND
terminal. The maximum input voltage should not exceed 30V. An electronic load or
resistive load can be used for evaluation or the intended system load can be con-
nected. Electronic loads attempt to sink current at 0V during startup, a resistive load or
constant resistance is recommended for startup evaluation. Connect the positive volt-
age terminal of the load to the V
OUT
terminal on the demo board and connect the neg-
ative 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 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 will begin to
switch. Apply greater than 4V to the input for proper operation, a minimum load
is required to regulate the output to 3.3V. Detailed information is provided in the
MCP16301 data sheet (DS25004) for minimum load requirements for light load
conditions.
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 High Side Drive Boost Circuit 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 startup, 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 short time to recharge
the boost capacitor.
