TS4956 datasheet(5/51 Pages) STMICROELECTRONICS

5 / 51 page

TS4956

Typical application schematic

5/51

2.1

I2C interface

The TS4956 uses a serial bus, which conforms to the I²C protocol (the TS4956 must be

powered when it is connected to I²C bus), to control the chip’s functions via two wires: Clock

and Data.

The Clock line and the Data line are bidirectional (open-collector) with an external chip pull-

up resistor (typically 10 k

Ω). The maximum clock frequency in fast-mode specified by the I²C

standard is 400kHz, and this frequency is supported by the TS4956. In this application, the

TS4956 is always the slave device and the controlling MCU is the master device.

The I2CVCC pin determines the power supply of the TS4956’s I2C interface. The voltage

connected to this pin must be equal or less than the TS4956 power supply voltage VCC. The

minimum value of the I2CVCC voltage is 2.7V.

When the I2CVCC pin is connected to an I2C voltage, the TS4956 is ready to communicate

via the I2C bus.

When the I2CVCC pin is connected to the ground, the TS4956 is in total standby mode, with

an ultra low standby current on the order of a few nanoamperes. In this condition the

TS4956 cannot receive I2C command from the I2C bus.

In both cases, pins SDA and SCL must respect logic HI or logic LOW thresholds (not

floating) presented in

Table 3 on page 2, in order for the circuit to function properly.

Table on page 5 summarizes the pin descriptions for the I²C bus interface.

2.1.1

I²C operation description

The host MCU can write into the TS4946 control register to control the TS4956 and read

from the control register to get the current configuration of the TS4956. The TS4956 is

addressed by a single byte consisting of a 7-bit slave address and an R/W bit. The TS4956

control register address is $5Dh.

Table 6.

The first byte after the START message for addressing the device

In order to write data into the TS4956 control register, after the “start” message the MCU

must send the following data:

●

send byte with the I²C 7-bit slave address and with the R/W bit set low

●

send the data (control register setting)

All bytes are sent with MSB bit first. The transfer of written data ends with a “stop” message.

When transmitting several data, the data can be written with no need to repeat the “start”

message and addressing byte with the slave address.

Table 5.

I²C bus interface: pin descriptions

Functional description

SDA

This is the serial data pin

SCL

This is the clock input pin

I2CVCC

I2C interface power supply

101

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