MP2117

– 1.25MHZ, 2.2A SYNCHRONROUS STEP-DOWN SWITCHER

END OF LIFE, REFER TO MP1605

MP2117 Rev. 0.92

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8

6/20/2022

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modulates the power transferred to the load by

changing the inductor peak current based on the

feedback error voltage. During normal operation,

the main switch is turned on for a certain time to

ramp the inductor current at each rising edge of

the internal oscillator, and switched off when the

peak inductor current is above the error voltage.

When the main switch is off, the synchronous

rectifier will be turned on immediately and stay on

until the next cycle starts.

Dropout Operation

The MP2117 allows the main switch to remain on

for more than one switching cycle and increases

the duty cycle while the input voltage is dropping

close to the output voltage. When the duty cycle

reaches 100%, the main switch is held on

continuously to deliver current to the output up to

the PFET current limit. The output voltage then

becomes the input voltage minus the voltage

drop across the main switch and the inductor.

Short Circuit Protection

When the output is shorted to ground, the

oscillator frequency is reduced to prevent the

inductor current from increasing beyond the

PFET current limit. The PFET current limit is also

reduced to lower the short circuit current. The

frequency and current limit will return to the

normal values once the short circuit condition is

removed and the feedback voltage reaches 0.6V.

Maximum Load Current

The MP2117 can operate down to 2.5V input

voltage; however the maximum load current

decreases at lower input due to a large IR drop

on the main switch and synchronous rectifier.

The slope compensation signal reduces the peak

inductor current as a function of the duty cycle to

prevent sub-harmonic oscillations at duty cycles

greater than 50%. Conversely, the current limit

increases as the duty cycle decreases.

Power OK

The MP2117 provides an open-drain PWROK

output that goes high after the output reaches

regulation during startup. PWROK goes low after

the output goes out of regulation by ±10% or

when device enters shutdown. There is 50µsec

deglitch timer built in to avoid PWROK false

triggered during load transient.

Enable Control

MP2117 has a dedicated Enable control pin. By

pulling it to high or low, the IC can be enabled

and disabled by EN. Tie EN to VIN by proper

voltage divider for automatic start up as Figure 2

shows. And make sure that:

EN2

IN

EN1

EN2

R

Max. EN Threshold<V

6V

(R

R

)



+

Figure 2