ZL2103ALAF datasheet(24/28 Pages) RENESAS

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ZL2103

FN6966 Rev 5.00

Page 24 of 28

May 3, 2011

I2C/SMBus Communications

The ZL2103 provides an I2C/SMBus digital interface that enables

the user to configure all aspects of the device operation as well

as monitor the input and output parameters. The ZL2103 can be

used with any standard 2-wire I2C host device.

In addition, the device is compatible with SMBus version 2.0 and

includes an SALRT line to help mitigate bandwidth limitations

related to continuous fault monitoring. Pull-up resistors are

required on the I2C/SMBus as specified in the SMBus 2.0

specification. The ZL2103 accepts most standard PMBus

commands. When controlling the device with PMBus commands,

it is recommended that the enable pin is tied to SGND.

I2C/SMBus Device Address Selection

When communicating with multiple devices using the

I2C/SMBus interface, each device must have its own unique

address so the host can distinguish between the devices. The

device address can be set according to the pin-strap options

listed in Table 14. Address values are right-justified.

If additional device addresses are required, a resistor can be

connected to the SA pin according to Table 15 to provide up to 30

unique device addresses.

Digital-DC Bus

The Digital-DC Communications (DDC) bus is used to

communicate between Zilker Labs Digital-DC devices. This

dedicated bus provides the communication channel between

devices for features such as sequencing and fault spreading. The

DDC pin on all Digital-DC devices in an application should be

connected together. A pull-up resistor is required on the DDC bus

in order to guarantee the rise time as expressed in Equation 13:

Where RPU is the DDC bus pull-up resistance and CLOAD is the bus

loading. The pull-up resistor may be tied to VRA or to an external

3.3V or 5V supply as long as this voltage is present prior to or

during device power-up. As rules of thumb, each device

connected to the DDC bus presents approximately 10pF of

capacitive loading, and each inch of FR4 PCB trace introduces

approximately 2pF. The ideal design will use a central pull-up

resistor that is well matched to the total load capacitance. In

power module applications, the user should consider whether to

place the pull-up resistor on the module or on the PCB of the end

application.

The minimum pull-up resistance should be limited to a value that

enables any device to assert the bus to a voltage that will ensure

a logic 0 (typically 0.8V at the device monitoring point) given the

pull-up voltage (5V if tied to VRA) and the pull-down current

capability of the ZL2103 (nominally 4mA).

TABLE 14. SMBus DEVICE ADDRESS SELECTION

SA PIN SETTING

SMBus ADDRESS

LOW

0x20

OPEN

0x21

HIGH

0x22

(EQ. 13)

Rise time

RPU

CLOAD



s



TABLE 15. SMBus ADDRESS VALUES

RSA

)

SMBus Address

0x20

0x21

12.1

0x22

13.3

0x23

14.7

0x24

16.2

0x25

17.8

0x26

19.6

0x27

21.5

0x28

23.7

0x29

26.1

0x2A

28.7

0x2B

31.6

0x2C

34.8

0x2D

38.3

0x2E

42.2

0x2F

46.4

0x30

51.1

0x31

56.2

0x32

61.9

0x33

68.1

0x34

0x35

82.5

0x36

90.9

0x37

100

0x38

110

0x39

121

0x3A

133

0x3B

147

0x3C

162

0x3D

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