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LPS3015

High Voltage Input Integrated Switch Step-Down Regulator

Microchip Technology 

MCP16301

VIN

CIN

BG

REF

VREG

VOUT

SS OTEMP

VREF

Boost

Pre

Charge

500 kHz OSC

RTOP

RBOT

+

FB

Amp

-

-

Comp

+

RCOMP

Precharge

Overtemp

VREF CCOMP

EN

+

-

SHDN all blocks

GND

S

PWM

Latch

HS

Drive

R

+

CS

+

RSENSE

Slope

Comp

BOOST Boost Diode

CBOOST

SW

Schottky

Diode

VOUT

COUT

GND

FIGURE 4-1:

MCP16301 Block Diagram.

4.2 Functional Description

4.2.1

STEP-DOWN OR BUCK

CONVERTER

The MCP16301 is a non-synchronous, step-down or

buck converter capable of stepping input voltages

ranging from 4V to 30V down to 2.0V to 15V 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 (ESR),

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

DC voltage is applied to 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.

IL

SW

L

VIN

+

-

Schottky

Diode

VOUT

COUT

IL

IOUT

0

VIN

SW

VOUT

on off on off on

Continuous Inductor Current Mode

IL

0

IOUT

VIN

SW

on off on off on

Discontinuous Inductor Current Mode

FIGURE 4-2:

Step-Down Converter.

DS25004A-page 12

© 2011 Microchip Technology Inc.

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