MCP1612-I Просмотр технического описания (PDF) - Microchip Technology

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MCP1612-I

Single 1A, 1.4 MHz Synchronous Buck Regulator

Microchip Technology 

MCP1612

5.0 APPLICATION CIRCUITS/INFORMATION

MCP1612 3.3V to 1.2V Synchronous Buck Converter

3.3VIN ±10%

CIN

10 µF

Ceramic

ON

OFF

CBYP

0.1 µF

Ceramic

1

VIN

MCP1612

10

8 L = 3.3 µH

Lx

2

VCC

7

PGND

3

SHDN

6

AGND

4

Comp

5

FB

1.2V VOUT @ 1A

COUT

10 µF

Ceramic

100 k

200 k

25 k

1000 pF

FIGURE 5-1:

Typical Application Circuit.

5.1 Typical Applications

The MCP1612 buck controller can be used in several

different applications where a voltage that is lower than

the supply voltage is required. Its small size, low cost

and high efficiency make the MCP1612 a good choice

for densely-packaged applications. The input voltage

range, low-dropout voltage and low shutdown current

make this part perfectly suited for battery-powered

applications.

5.2 Design Example

The step-by-step design of a buck converter with the

following parameters is presented to illustrate how

easy the MCP1612 is to use.

Input voltage = 3.3V

Output voltage = 1.2V

Output current = 0A to 1A

Switching frequency = 1.4 MHz

5.2.1 SETTING OUTPUT VOLTAGE

The output voltage of the MCP1612 is set by using an

external resistor-divider network. The voltage present

at FB is internally compared to a 0.8V reference

voltage. A 200 kresistor is recommended for R2, the

lower-end of the voltage divider. Using higher-value

resistors will make the circuit more susceptible to noise

on the FB pin. Lower-value resistors can be used, if

necessary.

Equation 5-1, used to calculate the output voltage, is

shown below.

EQUATION 5-1:

Where:

R1

=

R2







V----O----U----T-

VFB

–

1

VOUT = desired output voltage

VFB = MCP1612 internal reference

voltage

R1 = top resistor value

R2 = bottom resistor value

For this example:

VOUT = 1.2V

VFB = 0.8V

R2 = 200 k

R1 = 100 k

The MCP1612 is capable of a 15% duty cycle.

Instability may result when the duty cycle is below 15%.

If less than 15% duty cycle operation is needed, care

must be taken to ensure stable operation.

 2004-2013 Microchip Technology Inc.

DS21921C-page 11

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