MCP16331 datasheet(12/40 Pages) MICROCHIP

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MCP16331

DS20005308B-page 12

 2014 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

(CBOOST) 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 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

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 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

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 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 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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