MP8845C – 5A HIGH EFFICIENT SYNC. STEP DOWN SWITCHER WITH I2C

MP8845C Rev. 1.02

www.MonolithicPower.com

16

4/25/2014

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2014 MPS. All Rights Reserved.

I2C INTERFACE

for smart design. MPS has a GUI control

Interface is shown in figure 2. Its install process

and usage can be found in another document

“MP8845 Software Guide”.

I

0x39H internally. If need other slave address,

please contact with factory.

Table 2—I

Hex

A7

A6 A5 A4 A3 A2 A1 A0

W 0x38

R 0x39

0

0

1

1

1

0

0

R/W

Address

0x1C

I

Except MP8845C EN pin can start up and

controlled enable. When writing D7=0, the

convertor is off. When writing D7=1, the

convertor is on. Both external EN and I2C EN

can control the converter. Only when both EN is

high, the converter works.

OUTPUT VOLTAGE SELECT

There is no need to set feedback resistors to get

different output voltage. The default output

voltage is 1.1V, but it can be set from 0.6V to

change output voltage is:

1. Write Go bit (Reg02 Syscntlreg2 [D5]) to 1.

This action means output voltage can be set

another value which is not default Vo voltage;

2.

Write Output reference bit (Reg00 VSEL

[D6 ： D0]). The output voltage can be

changed refer to Table 1. Output Voltage

Chart.

SWITCHING FREQUENCY

The default switching frequency of MP8845C is

2.2MHz; however the frequency can also be

changed based on the application. By writing

Switching frequency bits (Reg01 SysCntlreg1

[D7:D5],

switching

frequency

can

be

programmed for one of six possible value. Their

corresponding data can be found in Table 1.

Reg01.

PGOOD CONFIGURE

MP8845C has an option to uses PG_LOHI

function. This function can be wrote Pglohi bit

(Reg01 Syscntlreg1 [D2]). The default value is 1,

“PGOOD” will sense both a positive and negative

excursion of Vo from the reference. If writing this

bit to 0, “PGOOD” only sense a negative voltage

excursion of Vo from the reference.

INPUT OVER VOLTAGE PROTECTION

MP8845C has an option to uses VIN_OVP

function. This function can be wrote Vinovp bit

(Reg01 Syscntlreg1 [D1]). The default value is 0,

VIN OVP function is enabled. When Vin voltage

is higher than 6.1V, the converter will be disabled.

After Vin voltage recover to 5.8V, the converter

will re-start. If Vinovp bit is set to 1, the Vin OVP

will be disable. It will not stop converter even Vin

voltage excess its safe range.

FORCED CCM

The MP8845C has auto PFM mode and forced

CCM. This function can be wrote Mode bit

(Reg01 Syscntlreg1 [D0]). The default value is 0,

auto PFM mode is selected. Consider smaller Vo

ripple and regulation for full load range, forced

CCM mode is recommended. Set this bit to 1 will

disable the PFM mode.

OUTPUT DISCHARGE

MP8845C has output discharge function. Write

Out-dis bit (Reg02 SysCntlreg2 [D4]) can change

the output discharge mode. The default value is 0

and just discharge the Vo by its load when EN is

low. Writing D4=1 can enable the function, and

then the output voltage can be discharged by

internal pull down resistance.