Datasheet

MCP16331
DS20005308C-page 12  2014-2016 Microchip Technology Inc.
4.0 DETAILED DESCRIPTION
4.1 Device Overview
The MCP16331 is a high input voltage step-down
regulator, capable of supplying 500 mA to a regulated
output voltage, from 2.0V to 24V. 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 (C
BOOST
) whose
energy is supplied from a fixed voltage, ranging between
3.0V and 5.5V, typically the input or output voltage of the
converter. For applications with an output voltage out
-
side 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 out
-
put 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
Table 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, input voltage, and the
maximum output current.
4.1.4 ENABLE INPUT
The enable input is used to disable the device while
connected to GND. If disabled, the MCP16331 device
consumes a minimal current from the input.
4.1.5 SOFT START
The internal reference voltage rate of rise is controlled
during start-up, 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 4.1V and operate down to 3.6V. Hysteresis is
added to prevent starting and stopping, during start-up,
as a result of loading the input voltage source.
4.1.7 OVERTEMPERATURE
PROTECTION
Overtemperature protection limits the silicon die
temperature to +160°C by turning the converter off. The
normal switching resumes at +130°C.