Microchip Technology ADM00427 Benutzerhandbuch
MCP16323 Evaluation Board User’s Guide
DS52029A-page 12
2011 Microchip Technology Inc.
A copper via, labeled INJ, connected between the 10Ω injection resistor (R1) and the
R
R
top
resistor can be populated to allow a convenient injection point for stability analysis.
A copper via, labeled Enable, connected to the enable input on the device can be pop-
ulated and used to turn the MCP16323 on and off. Turning the device on (Enable >
2.2V) when the undervoltage lockout threshold is met (V
ulated and used to turn the MCP16323 on and off. Turning the device on (Enable >
2.2V) when the undervoltage lockout threshold is met (V
IN
> 5.75V), will enable the
device. This pin must be pulled low (Enable < 0.8V) to disable the device.
A copper via, labeled SW, connected to the switch node of the device can be populated
to analyze the switch node of the device.
A copper via, labeled SW, connected to the switch node of the device can be populated
to analyze the switch node of the device.
2.2
GETTING STARTED
The MCP16323 Evaluation Board is fully assembled and tested to evaluate and dem-
onstrate the MCP16323 operational capabilities.
onstrate the MCP16323 operational capabilities.
2.2.1
Power Input and Output Connection
2.2.1.1
POWERING THE MCP16323 EVALUATION BOARD
The MCP16323 Evaluation Board is fully assembled, tested and ready to begin evalu-
ation. Apply positive input voltage to the V
ation. Apply positive input voltage to the V
IN
terminal and its return to the GND terminal.
The maximum input voltage should not exceed 18V. An electronic load or resistive load
can be used for evaluation, or the intended system load can be connected. Electronic
loads attempt to sink current at 0V during startup; a resistive load or constant resis-
tance is recommended for startup evaluation. Connect the positive voltage terminal of
the load to the V
can be used for evaluation, or the intended system load can be connected. Electronic
loads attempt to sink current at 0V during startup; a resistive load or constant resis-
tance is recommended for startup evaluation. Connect the positive voltage terminal of
the load to the V
OUT
terminal on the MCP16323 Evaluation 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:
1. Apply greater than 6V to the input for proper operation, no minimum load is
1. Apply greater than 6V to the input for proper operation, no minimum load is
required to regulate the output to 3.0V.
2. The EN input is internally pulled up to a low voltage internal source enabling the
device. To disable the device, the EN input can be pulled below 0.8V.
3. The measured output voltage should be 3.0V typical. Adjusting the input voltage
and load should not cause the output to vary significantly over the operating
range of the converter.
range of the converter.
2.2.2
How the MCP16323 High-Side Drive Boost Circuit Operates
The MCP16323 integrates both high-side and low-side, low resistance N-Channel
MOSFETs. A high-side or floating supply is needed to drive the gate of the high-side
N-Channel MOSFET above the input voltage to turn it on. The evaluation board uses
the output voltage to charge the boost cap while the inductor current flows. 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, ramp-
ing current into the inductor.
The worst case operating conditions for charging the boost capacitor occur at minimum
V
MOSFETs. A high-side or floating supply is needed to drive the gate of the high-side
N-Channel MOSFET above the input voltage to turn it on. The evaluation board uses
the output voltage to charge the boost cap while the inductor current flows. 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, ramp-
ing 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
(6V), there is not enough headroom 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.
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.