ZL2008 datasheet(13/43 Pages) RENESAS

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ZL2008

FN6859 Rev 4.00

Page 13 of 43

April 29, 2011

Output Voltage Selection

STANDARD MODE

The output voltage may be set to any voltage between 0.6V and

5.0V provided that the input voltage is higher than the desired

output voltage by an amount sufficient to prevent the device

from exceeding its maximum duty cycle specification. Using the

pin-strap method, VOUT can be set to any of nine standard

voltages as shown in Table 2.

The resistor setting method can be used to set the output voltage

to levels not available in Table 2. Resistors R0 and R1 are

selected to produce a specific voltage between 0.6V and 5.0V in

10mV steps. Resistor R1 provides a coarse setting and resistor

R0 provides a fine adjustment, thus eliminating the additional

errors associated with using two 1% resistors (this typically adds

approx 1.4% error).

To set VOUT using resistors, follow the steps below to calculate an

index value and then use Table 3 to select the resistor that

corresponds to the calculated index value as follows:

1. Calculate Index1:

Index1 = 4 x VOUT (VOUT in 10mV steps)

2. Round the result down to the nearest whole number.

3. Select the value of R1 from Table 3 using the Index1 rounded

value from step 2.

4. Calculate Index0:

5. Index0 = 100 x VOUT – (25 x Index1)

6. Select the value of R0 from Table 3 using the Index0 value

from Step 4.

Example from Figure 9: For VOUT = 1.33V,

Index1 = 4 x 1.33V = 5.32;

From Table 3, R1 = 16.2k



Index0 = (100 x 1.33V) – (25 x 5) = 8;

From Table 3, R0 = 21.5k



SMBUS MODE

The output voltage may be set to any value between 0.6V and

5.0V using a PMBus command over the I2C/SMBus interface.

See Application Note AN2033 for details.

TABLE 2. Output Voltage Pin-strap Settings

LOW

(V)

OPEN

(V)

HIGH

(V)

LOW

0.6

0.8

1.0

OPEN

1.2

1.5

1.8

HIGH

2.5

3.3

5.0

TABLE 3. Output Voltage Resistors Settings

Index

R0 or R1

)

010

12.1

13.3

14.7

16.2

617.8

19.6

821.5

23.7

26.1

28.7

31.6

34.8

38.3

42.2

46.4

51.1

56.2

61.9

68.1

82.5

90.9

100

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