MAX77813 datasheet(21/30 Pages) MAXIM

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Clock Stretching

In general, the clock signal generation for the I2C bus is

the responsibility of the master device. I2C specification

allows slow slave devices to alter the clock signal by

holding down the clock line. The process in which a slave

device holds down the clock line is typically called clock

stretching. The device does not use any form of clock

stretching to hold down the clock line.

General Call Address

The device does not implement I2C specification “General

Call Address.” If the device sees “General Call Address

(00000000b)” it does not issue an ACKNOWLEDGE (A).

Communication Speed

The device provides I2C 3.0-compatible (3.4MHz) serial

interface.

● I2C Revision 3 Compatible Serial Communications

Channel

• 0Hz to 100kHz (Standard mode)

• 0Hz to 400kHz (Fast mode)

• 0Hz to 1MHz (Fast-mode plus)

• 0Hz to 3.4MHz (High-speed mode)

● Does not utilize I2C Clock Stretching

Operating in standard mode, fast mode, and fast-mode

plus does not require any special protocols. The main

consideration when changing the bus speed through

this range is the combination of the bus capacitance and

pullup resistors. Higher time constants created by the

bus capacitance and pullup resistance (C x R) slow the

bus operation. Therefore, when increasing bus speeds,

the pullup resistance must be decreased to maintain a

reasonable time constant. See the Pullup Resistor Sizing

section of the I2C revision 3.0 specification for detailed

guidance on the pullup resistor selection. In general, for

bus capacitances of 200pF, a 100kHz bus needs 5.6kΩ

pullup resistors, a 400kHz bus needs about 1.5kΩ pullup

resistors, and a 1MHz bus needs 680Ω pullup resistors.

Note that the pullup resistor is dissipating power when the

open-drain bus is low. The lower the value of the pullup

resistor, the higher the power dissipation (V2/R).

Operating in high-speed mode requires some special con-

siderations. For the full list of considerations, see the I2C

3.0 specification. The major considerations with respect to

the MAX77813 are:

● I2C bus master use current source pullups to shorten

the signal rise times.

● I2C slave must use a different set of input filters on

its SDA and SCL lines to accommodate for the higher

bus speed.

● The communication protocols need to utilize the high-

speed master code.

At power-up and after each STOP condition, the device

input filters are set for standard mode, fast mode, or

fast-mode plus (i.e., 0Hz to 1MHz). To switch the input

filters for high-speed mode, use the high-speed master

code protocols that are described in the Communication

Protocols section.

Communication Protocols

The device supports both writing and reading from its reg-

isters. The following sections show the I2C communica-

tion protocols for each functional block. The power block

uses the same communication protocols.

MAX77813

5.5V Input, 2A, High-Efficiency

Buck-Boost Converter

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