MP8861 – 2.85V - 18V, 6A, SYNCHRONOUS, STEP-DOWN CONVERTER

MP8861 Rev. 1.1

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25

5/28/2020

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3) Reg02 SysCntlreg2

Register 02 is the second system control

register.

The highest two bits of PG Deglitch Time D[7:6]

defines the power good signal rising and falling

edge delay times. When output OVP or UVP is

triggered, the PG signal turns low or high after a

delay time. There are four levels of PG delay

time that can be programmed by the I2C in

different conditions.

The two Switching Frequency bits D[5:4] are

used for switching frequency selection. The

MP8861 supports up to 1.25MHz of switching

frequency by setting the two bits to 11. The

MP8861 maximum programmable switching

frequency is limited by internal minimum on-

time (see Table 1).

The bit Soft Stop defines the output voltage

discharge behavior after EN shutdown. When

Soft Stop is set to 0, the output voltage is not

controlled after EN shutdown. When Soft Stop

is set to 1, the output voltage is discharged

linearly to zero with the set soft-stop time.

The lowest three bits, Current Limit Adjust

D[2:0], are used for peak and valley current-

limit selection. There are eight levels of current

limit that can be selected for different

application conditions.

NAME

BITS

DEFAULT

DESCRIPTION

PG Deglitch

Time

D[7:6]

11

Power good signal rising and falling edges’ delay time. When FB or

VOUT is out of regulation window, the PG comparator is triggered, but

needs a delay time before the PG signal can turn high or low.

D[7:6]

PG Deglitch

D[7:6]

PG Deglitch

00

<1μs

10

12μs

01

6μs

11

30μs

Switching

Frequency

D[5:4]

00

Switching frequency set bit. There is no dedicated frequency oscillator

inside the part. The switching frequency is fairly fixed by controlling the

TON timer.

D[5:4]

Frequency

D[5:4]

Frequency

00

500kHz

10

1MHz

01

750kHz

11

1.25MHz

Soft Stop

D[3]

0

This bit defines the VOUT discharge behavior after EN shutdown. 0

means VOUT is not controlled after EN shutdown. 1 means VOUT is

discharged linearly to zero with the set soft-stop time.

Current Limit

Adjust

D[2:0]

001

D[2:0]

Valley Current Limit (A)

D[2:0]

Valley Current Limit (A)

000

9.6

100

5.1

001

8.4

101

4.2

010

7.2

110

3.6

011

6

111

3