UCS1002-3 datasheet(99/114 Pages) MICROCHIP

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DS20006852A-page 99

UCS1002-3

11.0 COMMUNICATIONS

11.1

Operating Mode

The UCS1002-3 can operate in SMBus mode (see

Section 11.2 “SMBus Operating Mode”) or Stand-

Alone

mode

(see

Section 11.3

“Stand-Alone

Operating

Mode”).

The

resistor

the

COMM_SEL/ILIM pin determines the operating mode

and the hardware-set ILIM setting as shown in

Table 11-1. Unless connected to GND or VDD, the

resistors in Table 11-1 are pull-down resistors.

11.2

SMBus Operating Mode

When the COMM_SEL/ILIM pin is directly connected to

ground or though a pull-down resistor with a value of

33 k

 or below as listed in Table 11-1, the UCS1002-3

communicates via the SMBus or I2C communications

protocols.

11.2.1

SYSTEM MANAGEMENT BUS

In SMBus mode, the UCS1002-3 communicates with a

host controller. The SMBus is a two-wire serial

communication protocol between a computer host and

its peripheral devices. A detailed timing diagram is

shown in Figure 11-1. Stretching of the SMCLK signal

is supported; however, the UCS1002-3 does not

stretch the clock signal.

Note:

If it is necessary to connect the

COMM_SEL/ILIM pin to VDD via a pull-up

resistor, it is recommended that this

resistor value does not exceed 100 k

.

TABLE 11-1:

UCS1002-3 COMMUNICATION MODE AND ILIM SELECTION

SELECTION Resistor ±5%

ILIM Setting

Communications Mode

GND

500 mA

SMBus – see Section 11.2.1.2

10 k

 pull-down resistor

900 mA

SMBus – see Section 11.2.1.2

12 k

 pull-down resistor

1000 mA

SMBus – see Section 11.2.1.2

15 k

 pull-down resistor

1200 mA

SMBus – see Section 11.2.1.2

18 k

 pull-down resistor

1500 mA

SMBus – see Section 11.2.1.2

22 k

 pull-down resistor

1800 mA

SMBus – see Section 11.2.1.2

27 k

pull-down resistor

2000 mA

SMBus – see Section 11.2.1.2

33 k

 pull-down resistor

2500 mA

SMBus – see Section 11.2.1.2

47 k

 pull-down resistor

500 mA

Stand-Alone mode

56 k

 pull-down resistor

900 mA

Stand-Alone mode

68 k

 pull-down resistor

1000 mA

Stand-Alone mode

82 k

 pull-down resistor

1200 mA

Stand-Alone mode

100 k

 pull-down resistor

1500 mA

Stand-Alone mode

120 k

 pull-down resistor

1800 mA

Stand-Alone mode

150 k

 pull-down resistor

2000 mA

Stand-Alone mode

VDD (If a pull-up resistor is used, its

value must not exceed 100 k

.)

2500 mA

Stand-Alone mode

Note 1: Upon power-up, the UCS1002-3 does

not

respond

any

SMBus

communications for 5.5 ms. After this

time, full functionality is available.

2: When in the Sleep state, the first SMBus

read command sent to the UCS1002-3

device address wakes it. Any data sent to

the UCS1002-3 is ignored and any data

read from the UCS1002-3 must be

considered invalid. The UCS1002-3 is

fully functional 3 ms after this first read

command is sent. See Section 5.1.2

“Sleep State Operation”.

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