SDIO

SCL

P

STO

condition

START condition

S

P

SCL

SDIO

data

change

allowed

data

valid

data

change

allowed

data

valid

data

change

allowed

12

LM3535

SNVS598B – AUGUST 2010 – REVISED MARCH 2018

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7.4 Device Functional Modes

7.4.1 Shutdown

The LM3535 enters shutdown mode if HWEN pin is held low. In this mode, the LM3535 has a shutdown current

of 1.7 µA. I2C communication is not possible when in shutdown.

7.4.2 Standby

The LM3535 enters standby mode if HWEN pin is held high and when the ENx bits are set to 0. In this mode, the

LM3535 has a standby current of 1.7 µA. I2C communication is possible when in standby.

7.4.3 Active Mode

The LM3535 enters active mode if HWEN pin is held high and when any of the ENx bits are set to 1. When the

LM3535 is in pass-mode operation, the typical quiescent current drawn is 1.09 mA. When the LM3535 is in

boost-mode operation, the typical quiescent current drawn is 2.86 mA. I2C communication is possible when in

active mode.

7.5 Programming

7.5.1 I2C Compatible Interface

7.5.1.1 Data Validity

The data on SDIO line must be stable during the HIGH period of the clock signal (SCL). In other words, state of

the data line can only be changed when SCL is LOW.

Figure 17. Data Validity Diagram

A pullup resistor between the VIO line and SDIO of the controller must be greater than [(VIO – VOL) / 3 mA] to

meet the VOL requirement on SDIO. Using a larger pullup resistor results in lower switching current with slower

edges, while using a smaller pullup results in higher switching currents with faster edges.

7.5.1.2 Start and Stop Conditions

START and STOP conditions classify the beginning and the end of the I2C session. A START condition is

defined as SDIO signal transitioning from HIGH to LOW while SCL line is HIGH. A STOP condition is defined as

the SDIO transitioning from LOW to HIGH while SCL is HIGH. The I2C master always generates START and

STOP conditions. The I2C bus is considered to be busy after a START condition and free after a STOP condition.

During data transmission, the I2C master can generate repeated START conditions. First START and repeated

START conditions are equivalent, function-wise.

Figure 18. Start and Stop Conditions