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

MP8861 Rev. 1.1

www.MonolithicPower.com

19

5/28/2020

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I2C Control and Default Output Voltage

When the MP8861 is enabled, the output

voltage is determined by the FB resistors with a

programmed soft-start time. Afterward, the I2C

bus can communicate with the master. If the

chip does not receive I2C communication signal

continuously, it can work well through FB and

perform behavior similar to a traditional non-I2C

part. The output voltage is determined by the

resistor dividers R1, R2, and FB reference

voltage. VOUT can be calculated using Equation

(3):

REF

OUT

R1 R2

VV

(

)

R2





(3)

Note that the output voltage cannot be set

higher than an absolute OVP threshold

(typically 6.5V).

I2C Slave Address

To support multiple devices used on the same

I2C bus, A0 can be used to select four different

addresses. A resistor divider from VCC to GND

can achieve an accurate reference voltage.

Connect A0 to this reference voltage to set a

different I2C slave address (see Figure 7). The

internal circuit changes the I2C address

accordingly.

When the master sends an 8-bit address value,

the 7-bit I2C address should be followed by 0 or

1 to indicate a write or read operation,

respectively. Table 2 shows the recommended

I2C address selection by the A0 voltage.

Figure 7: I2C Slave Address Selection Set-Up

Table 2: Recommended I2C Slave Address

Selection by A0 Resistor Divider

A0 Upper

Resistor

RA0_up (kΩ)

A0 Lower

Resistor

RA0_down (kΩ)

I2C Slave Address

Binary

Hex

No

connect

No connect

110 0001

61H

500

300

110 0011

63H

300

500

110 0101

65H

100

No connect

110 0111

67H