ZL8101ALAF datasheet(28/36 Pages) RENESAS

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ZL8101

FN7832 Rev 1.00

Page 28 of 36

July 13, 2012

Voltage Margining

The ZL8101 offers a simple means to vary its output higher or

lower than its nominal voltage setting in order to determine

whether the load device is capable of operating over its specified

supply voltage range. The MGN command is set by driving the

MGN pin or through the I2C/SMBus interface. The MGN pin is a

TTL-compatible input that is continuously monitored and can be

driven directly by a processor I/O pin or other logic-level output.

The ZL8101’s output will be forced higher than its nominal set

point when the MGN command is set HIGH, and the output will

be forced lower than its nominal set point when the MGN

command is set LOW. Default margin limits of VNOM ±5% are

pre-loaded in the factory, but the margin limits can be modified

through the I2C/SMBus interface to as high as VNOM + 10% or as

low as 0V, where VNOM is the nominal output voltage set point

determined by the V0 and V1 pins. A safety feature prevents the

user from configuring the output voltage to exceed VNOM + 10%

under any conditions.

The margin limits and the MGN command can both be set

individually through the I2C/SMBus interface. Additionally, the

transition rate between the nominal output voltage and either

margin limit can be configured through the I2C interface. Please

refer to Application Note AN2033 for detailed instructions on

modifying the margining configurations.

External Voltage Monitoring

The voltage monitoring (VMON) pin is available to monitor the

voltage supply for the external driver IC. If the voltage falls below

a predefined threshold value (adjustable through a PMBus

command), the device will fault and stop sending PWM signals. A

1/16 external resistor divider is required to keep the maximum

voltage on this pin to less than 1.15V.

I2C/SMBus Communications

The ZL8101 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 ZL8101 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. The ZL8101 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 SMBus 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 17. Address values are right-justified.

TABLE 17. TRACKING MODE CONFIGURATION

RSS

(kΩ)

UVLO

(V)

TRACKING RATIO

(%)

UPPER TRACK LIMIT

RAMP-UP/RAMP-DOWN BEHAVIOR

19.6

4.5

100

Limited by target voltage

Output not allowed to decrease before PG

21.5

Output will always follow VTRK

23.7

Limited by VTRK pin voltage

Output not allowed to decrease before PG

26.1

Output will always follow VTRK

28.7

Limited by target voltage

Output not allowed to decrease before PG

31.6

Output will always follow VTRK

34.8

Limited by VTRK pin voltage

Output not allowed to decrease before PG

38.3

Output will always follow VTRK

42.2

10.8

100

Limited by target voltage

Output not allowed to decrease before PG

46.4

Output will always follow VTRK

51.1

Limited by VTRK pin voltage

Output not allowed to decrease before PG

56.2

Output will always follow VTRK

61.9

Limited by target voltage

Output not allowed to decrease before PG

68.1

Output will always follow VTRK

Limited by VTRK pin voltage

Output not allowed to decrease before PG

82.5

Output will always follow VTRK

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