MCP16331 datasheet(13/48 Pages) MICROCHIP

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DS20005308D-page 13

MCP16331

4.0

DETAILED DESCRIPTION

4.1

Device Overview

The MCP16331 device is a high input voltage step-down

regulator, capable of supplying 500 mA to a stable out-

put 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 MOS-

FET on and off. The power for this driver is derived from

an external boost capacitor (CBOOST) whose energy is

supplied from a fixed voltage, ranging between 3.0V and

5.5V, typically the input or output voltage of the con-

verter. 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.

4.1.1

INTERNAL REFERENCE VOLTAGE

(VREF)

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 the 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 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 amount of 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.

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