MP2166

– 6V, DUAL 2A/2A OR 3A/1A, SYNC, BUCK REGULATOR WITH PG AND SS

MP2166 Rev. 1.0

www.MonolithicPower.com

14

3/14/2017

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© 2017 MPS. All Rights Reserved.

OPERATION

The MP2166 is a fully integrated, dual-channel,

synchronous,

step-down

converter.

Both

channels use peak-current-mode control with

internal

compensation

for

fast

transient

response and cycle-to-cycle current limit.

The MP2166 is optimized for low-voltage,

portable applications where efficiency and small

size are critical.

180°Out-of-Phase Operation

The MP2166 operates the two channels in 180°

out-of-phase operation to reduce input current

ripple so a smaller input bypass capacitor can

be used. When both channels operate in CCM,

two internal clocks are used (see Figure 2). The

high-side MOSFET is turned on at the clock

rising edge of the corresponding channel.

CLK1

CLK2

SW1

SW2

t

CLk1, 2 has a 180

Figure 2: 180°Out-of-Phase Operation

At low dropout, when the switching frequency is

stretched out for each channel, the MP2166

runs at a fixed-off time with its own independent

switching frequency. After the input voltage

rises high again, frequency stretch mode ends,

and PWM mode resumes and synchronizes

with the master oscillator for out-of-phase

operation.

Light-Load Operation

In light-load condition, the MP2166 can work in

two different operating modes by setting CCM

to different statuses.

The

MP2166

works

in

forced

continuous

conduction mode (CCM) when the CCM pin is

pulled higher than 1.6V. The MP2166 works

with fixed frequency from no load to full load in

this mode. The advantage of CCM is the

controllable frequency and lower output ripple

at light load.

The shutdown current in forced CCM mode

(50

μA at 3.3V) is much higher than AAM mode

due to some internal circuits are active. It is

recommended to pull CCM pin LOW when part

is shutdown if the high shutdown current is

cared.

The MP2166 works in advanced asynchronous

mode (AAM) when CCM is pulled lower than

0.4V. AAM is used to optimize efficiency during

light-load and no-load conditions.

When AAM mode is enabled, the MP2166 first

enters

non-synchronous

operation

as

the

inductor current approaches zero at light load. If

the load decreases further or is at no load,

decrease to the set value, then the MP2166

enters AAM. In AAM, the internal clock is reset

and the crossover time is taken as the

benchmark of the next clock. When the load

value, the operation mode is in DCM or CCM,

which has a constant switching frequency.

AAM Mode

Inductor

Current

t

t

t

Load

Decreased

Forced CCM Mode

Inductor

Current

t

t

t

Load

Decreased

Figure 3: AAM Mode and Forced CCM Mode

Soft Start (SS)

The MP2166 has a built-in soft start that ramps

up the output voltage at a controlled slew rate,

preventing an overshoot at start-up. The soft-

start time is about 0.5ms, typically.

The soft-start time can also be programmed by

an external capacitor connected to SS, shown

in Equation (1):

 

 

 

 

μA

I

V

V

nF

C

ms

t

SS

RFF

SS

SS





(1)

the 3.2µA SS charge current.