MPQ2169B

– 6V, DUAL 1.4A/1.4A OR 2A/0.8A SYNC BUCK REGULATOR, AEC-Q100

MPQ2169B Rev. 1.0

MonolithicPower.com

18

12/20/2021

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OPERATION

The MPQ2169B 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 limiting.

The MPQ2169B is optimized for low-voltage,

portable applications where efficiency and small

size are critical.

180° Out-of-Phase Operation

The MPQ2169B operates the two channels

180° out of phase to reduce input current ripple.

This allows for a smaller input bypass capacitor

to be used. When both channels operate in

continuous

conduction

mode

(CCM),

two

internal clocks are used (see Figure 2). The

high-side MOSFET (HS-FET) turns on at the

clock

’s rising edge of the corresponding

channel.

CLK1

CLK2

SW1

SW2

t

CLK1 and CLK2 have a 180° phase shift

Figure 2: 180° Out-of-Phase Operation

If the switching frequency (fSW) is stretched out

for each channel during low-dropout mode, the

MPQ2169B runs with a fixed off time and an

independent fSW. After the input voltage (VIN)

rises high again, frequency stretch mode ends.

Subsequently, pulse-width modulation (PWM)

mode resumes and synchronizes with the

master oscillator for out-of-phase operation.

Forced

Continuous

Conduction

Mode

(FCCM)

The MPQ2169B works in forced continuous

conduction

mode

(FCCM)

with

a

fixed

frequency from no load to full load. The

advantages

of

FCCM

are

its

controllable

frequency and lower output ripple under light-

load conditions.

FCCM

Inductor

Current

t

t

t

Load

Decreased

Figure 3: FCCM

Enable (EN)

EN is a digital control pin that turns the

regulator on and off.

When EN is pulled below the falling threshold

voltage (typically 0.8V), the chip shuts down.

Pulling EN above the rising threshold voltage

(typically 0.9V) turns on the part. Do not float

the EN pin, since there is no internal resister

from EN to GND. If EN is floated, the

part’s

status

is

uncertain,

which

may

lead

to

unexpected behavior.

Soft Start (SS)

The MPQ2169B has a built-in soft start (SS)

that ramps up the output voltage (VOUT) at a

controlled slew rate, preventing overshoot at

start-up. The soft-start time (tSS) is typically

about 0.5ms.

tSS can also be configured by an external

capacitor connected to the SS pin, and can be

calculated using Equation (1):

SS

REF

SS

SS

C (nF) V

(V)

t (ms)

I(

μA)



=

(1)

Where CSS is the external SS capacitor, VREF is

the internal reference voltage (0.6V), and ISS is

the 3.2µA SS charge current.

Oscillator and SYNC Function

The internal oscillator frequency is set by a

single

external

resistor

(RFREQ)

connected

between FREQ and ground. The frequency-

setting resistor should be placed close to the

device. Figure 4 on page 19 shows the

relationship between fSW and RFREQ.