MCP16331 datasheet(13/40 Pages) MICROCHIP

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 2014 Microchip Technology Inc.

DS20005308B-page 13

MCP16331

FIGURE 4-1:

MCP16331 Block Diagram.

4.2

Functional Description

4.2.1

STEP-DOWN OR BUCK

CONVERTER

The MCP16331 is a non-synchronous, step-down or

buck converter capable of stepping input voltages

ranging from 4.4V to 50V down to 2.0V to 24V for

VIN > VOUT.

The integrated high side switch is used to chop or

modulate the input voltage using a controlled duty cycle

for output voltage regulation. High efficiency is

achieved by using a low-resistance switch, low forward

drop diode, low equivalent series resistance, inductor

and capacitor. When the switch is turned on, a DC

voltage is applied across the inductor (VIN - VOUT),

resulting in a positive linear ramp of inductor current.

When the switch turns off, the applied inductor voltage

is equal to -VOUT, resulting in a negative linear ramp of

inductor current (ignoring the forward drop of the

Schottky diode).

For

steady-state,

continuous

inductor

current

operation, the positive inductor current ramp must

equal the negative current ramp in magnitude. While

operating in steady state, the switch duty cycle must be

equal to the relationship of VOUT/VIN for constant

output voltage regulation, under the condition that the

inductor current is continuous, or never reaches zero.

For discontinuous inductor current operation, the

steady-state duty cycle will be less than VOUT/VIN to

maintain voltage regulation. The average of the

chopped input voltage or SW node voltage is equal to

the output voltage, while the average of the inductor

current is equal to the output current.

Schottky

Diode

COUT

CBOOST

Slope

Comp

PWM

Latch

Overtemp

Precharge

Comp

Amp

CCOMP

RCOMP

Drive

VREG

REF

VREF

OVERTEMP

Boost

Pre

Charge

500 kHz OSC

VOUT

RSENSE

GND

Boost Diode

VIN

RTOP

RBOT

BOOST

GND

VREF

SHDN all blocks

CIN

Note: EN has an internal pull up, so the device will start even if the EN pin is left floating.

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