MP26085

– CC/CV CONTROLLER

MP26085 Rev. 1.02

www.MonolithicPower.com

7

11/30/2015

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OPERATION

The MP26085 integrates a high precision band

gap

voltage

reference,

two

operational

amplifiers and a current source (Figure 1). It is

intended for use in a switching mode power

supply (SMPS) to realize constant current and

constant voltage control.

Voltage Reference

The voltage reference of MP26085 is 1.223V.

Voltage Regulation Loop

The voltage regulation is done by comparing

the feedback output voltage (resistor divider R1

and R2) to the voltage reference (1.223V). If it

is higher than 1.223V, the output of the voltage

loop operational amplifier decreases. The

optocoupler current increases and tends to

reduce the output voltage by the way of the

PWM controller.

Current Limitation Loop

The current limitation is performed by sensing

the voltage across the low ohmic value resistor

the R-divider composed by R3 and R4

voltage on the IREF pin the output of the

current loop operational amplifier decreases.

The optocoupler current increases and tends to

reduce the output voltage by the way of the

PWM controller.

Current Source

The current source of MP26085 is controlled by

the ICON pin

By connecting the ICON pin to the ground, the

current source is enabled. MP26085 mirrors the

source with the gain Ki=45. The current goes

R-divider, R3 and R4 (typical application circuit).

So, the current source is calculated as:

REF

SOURCE

V

IKi

R3 R4

=×

+

Then, we can offset the sensing output current

by a voltage equal to:

_OFFSET

SOURCE

VRif I

=×

This offset lowers the output current and this

function can be used to charge batteries with

different capacities.

Voltage

Reference

VREF

IN

COMP

GND

VFB

IFB

IREF

ICON

Regulator

Buffer

Figure 1—Block Diagram