PIC16F610 datasheet(4/20 Pages) MICROCHIP

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LED Lighting Solutions Design Guide

www.microchip.com/lighting

LED Lighting Solutions

Driving LEDs with a Boost Regulator

A boost regulator topology is used when the output voltage

of the converter must be equal to or greater than the input

voltage. A boost regulator is useful for driving a chain of

LEDs connected in series. It is beneficial to drive multiple

LEDs in series. This ensures that all LEDs receive the same

amount of current and will have the same brightness level.

Using a coupled inductor in the boost circuit reducing the

switching voltage requirements of the MOSFET switch.

The MCP1640 synchronous boost regulator can provide

a stable operating voltage for an LED from a single cell

alkaline battery.

The MCP1650 Boost Regulator uses an external switch

so that it can be used for any type of load. An additional

advantage of the MCP1650 in battery applications is the

Gated Oscillator Architecture which provides 2 duty cycles

reducing high-peak inductor current and output ripple

voltages. Input voltages above 3.8V engage a 56% duty

cycle and an 80% duty cycle when the input voltage drops

below 3.8V, extending battery life in these applications.

Driving LEDs with a Charge Pump

A charge pump power supply does not have inductors that

are required in other SMPS topologies. This provides a

more compact and less expensive circuit. The downside is

that charge pumps cannot supply large amounts of current

compared to the other topologies. Charge pump circuits

are most useful for backlighting applications. Common

applications include PCs, LCD displays and automotive

instrumentation.

MCP1252 Charge Pump Backlight

Demonstration Board (MCP1252DM-BKLT)

Demonstrates the use of a charge

pump device in an LED application

and acts as a platform to evaluate

the MCP1252 device in general.

Light intensity is controlled

uniformly through the use of ballast

resistors. A PIC10F206 MCU

provides an enable signal to the MCP1252 and accepts a

push-button input that allows the white LEDs to be adjusted

to five different light intensities.

Literature on the Web

■ MCP1252/3 Data Sheet, DS21572

■ MCP1252 Charge Pump Backlight Demo Board

User’s Guide, DS51551

■ MCP1252/3 Evaluation Kit User’s Guide, DS51313

■ DG10 – Power Solutions Design Guide, DS21913

Charge Pump LED Driver Using the MCP1252

C-

GND

VIN

VOUT

C+

SHDN

Single

Li-Ion

Cen

PWM Brightness

Control

MCP1252-ADJ

VIN

0.9V to 1.7V

VOUT

3.3V @ 100 mA

COUT

10 μF

976 KΩ

562 KΩ

CIN

4.7 μF

4.7 μH

VOUT

VFB

VIN

GND

MCP1640

MCP1640 Single Cell Synchronous Boost Regulator

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