Datasheet

 2011-2013 Microchip Technology Inc. DS20005004C-page 11
MCP16301/H
4.0 DETAILED DESCRIPTION
4.1 Device Overview
The MCP16301/H devices are high-input voltage
step-down regulators, capable of supplying 600 mA to
a regulated output voltage from 2.0V to 15V. Internally,
the trimmed 500 kHz oscillator provides a fixed
frequency, while the Peak Current Mode Control
architecture varies the duty cycle for output voltage
regulation. An internal floating driver is used to turn the
high-side integrated N-Channel MOSFET on and off.
The power for this driver is derived from an external
boost capacitor whose energy is supplied from a fixed
voltage ranging from 3.0V to 5.5V, typically the input or
output voltage of the converter. For applications with an
output voltage outside of this range, 12V for example,
the boost capacitor bias can be derived from the output
using a simple Zener diode regulator.
4.1.1 INTERNAL REFERENCE VOLTAGE
(V
REF
)
An integrated precise 0.8V reference combined with an
external resistor divider sets the desired converter
output voltage. The resistor divider range can vary
without affecting the control system gain. High-value
resistors consume less current, but are more
susceptible to noise.
4.1.2 INTERNAL COMPENSATION
All control system components necessary for stable
operation over the entire device operating range are
integrated, including the error amplifier and inductor
current slope compensation. To add the proper amount
of slope compensation, the inductor value changes
along with the output voltage (see Tabl e 5-1).
4.1.3 EXTERNAL COMPONENTS
External components consist of:
• input capacitor
• output filter (inductor and capacitor)
• freewheeling diode
• boost capacitor
• boost blocking diode
• resistor divider.
The selection of the external inductor, output capacitor,
input capacitor and freewheeling diode is dependent
upon the output voltage and the maximum output
current.
4.1.4 ENABLE INPUT
Enable input, (EN), is used to enable and disable the
device. If disabled, the MCP16301/H devices consume
a minimal current from the input. Once enabled, the
internal soft start controls the output voltage rate of rise,
preventing high-inrush current and output voltage
overshoot.
4.1.5 SOFT START
The internal reference voltage rate of rise is controlled
during startup, minimizing the output voltage overshoot
and the inrush current.
4.1.6 UNDERVOLTAGE LOCKOUT
An integrated Undervoltage Lockout (UVLO) prevents
the converter from starting until the input voltage is high
enough for normal operation. The converter will
typically start at 3.5V and operate down to 3.0V.
Hysteresis is added to prevent starting and stopping
during startup, as a result of loading the input voltage
source.
4.1.7 OVERTEMPERATURE
PROTECTION
Overtemperature protection limits the silicon die
temperature to +150°C by turning the converter off. The
normal switching resumes at +120°C.