MPQ2167 – 6V, 4A, FREQUENCY PROGRAMMABLE, BUCK CONVERTER, AEC-Q100 QUALIFIED

MPQ2167 Rev. 1.0

www.MonolithicPower.com

18

3/21/2019

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© 2019 MPS. All Rights Reserved.

Oscillator

The oscillating frequency of the MPQ2167 can be

programmed by an external frequency resistor.

The frequency resistor should be located

between FREQ and GND as close to the device as

possible.

Select the RFREQ value following the FSW vs. RFREQ

curve in the Typical Performance Characteristics

(TPC) section.

The MPQ2167 has a SYNCO pin, which can

output a 180° phase shift clock. This signal can

be used to synchronize other devices to keep the

same operation frequency but opposite phase,

which can reduce the total input current ripple.

Soft-Start and Output Discharge

The MPQ2167 has soft start (SS), which ramps up

the output voltage in a controlled slew rate when

EN goes high, avoiding overshoot at start-up.

When the soft-start period starts, an internal current

source charges the external soft-start capacitor.

When the SS voltage (VSS) falls below the internal

reference (VREF), the VSS overrides VREF as the

error amplifier reference. When VSS exceeds VREF,

VREF acts as the reference. After soft start finishes,

the MPQ2167 enters steady state. It can be used

for tracking and sequencing.

The SS time set by the external SS capacitor can

be calculated with equation (1):

SS

REF

SS

SS

C(nF) V

(V)

t(ms)

I( A)







(1)

Where CSS is the external SS capacitor, VREF is

the internal reference voltage (0.606V), and ISS is

the internal 4μA SS charge current.

When SS is floating, the SS time is 1ms following

the internal setting.

When disabled or in an input shutdown, the

MPQ2167 discharges the output voltage to GND

through an internal 100Ω resistor that is in parallel

to the LS-FET.

Pre-Bias Start-Up

At start-up, if VFB>VSS (which means the output

has pre-bias voltage), neither the high-side nor

low-side MOSFET is turned on until VSS is higher

than VFB.

100% Duty Cycle

The MPQ2167 can operate with 100% duty cycle,

which can help extend the battery life. When the

input voltage is too low to maintain the regulation

of the output, the device will completely turn on

the HS-FET to achieve maximum output voltage.

Power Good Indicator

The MPQ2167 has power good (PG) indication.

PG is the open drain of the MOSFET. In the

presence of an input voltage, the MOSFET turns

on so that PG is pulled to GND before a soft start

is ready. When the output voltage is within a ±

15% window of the rated voltage set by FB, PG

will be pulled up to VIN by an internal resistor after

a delay. If VFB moves outside the ±15% range

with a hysteresis, the device pulls PG low to

indicate a failure output status.

Over-Current Protection (OCP)

The MPQ2167 has a 6.7A cycle-by-cycle peak

current limit control. The inductor current is

monitored during a HS-FET on state. Once the

inductor current hits the current limit, the HS-FET

will be turned off immediately. Then the LS-FET

will be turned on to discharge the energy, and the

inductor current will decrease. The HS-FET will

not be on again until the inductor is lower than a

certain current threshold, which is called valley

current limit. It is very useful to prevent the

inductor current from running away and possibly

damaging the components.

When the valley current limit is triggered, the

OCP timer will start immediately. The OCP timer

is set at 100μs. Hitting the valley current limit

during each cycle during this 100μs time frame

will trigger SCP.

Short-Circuit Protection (SCP)

When a short circuit occurs, the MPQ2167 will

immediately hit its current limit. Meanwhile, the

output voltage drops until VFB is below 50%×VREF

(0.606V). Then the device will consider this an

output

dead

short

and

will

trigger

SCP

immediately. In SCP, the inductor current is

monitored during the HS-FET on state. Once the

inductor current hits the current limit, the HS-FET

will be turned off immediately. Then the LS-FET

will be turned on to discharge the energy and the

inductor current will decrease. The HS-FET will