ZL2008 datasheet(15/43 Pages) RENESAS

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ZL2008

FN6859 Rev 4.00

Page 15 of 43

April 29, 2011

DOSA VOLTAGE TRIM MODE

On a DOSA module, the VOUT setting follows Equation 3:

To maintain DOSA compatibility, the same scheme is used as with a

POLA module except the 10k

 resistor is replaced with a 8.66k

resistor as shown in Figure 12.

The DOSA mode VOUT settings are listed in Table 5.

Start-up Procedure

The ZL2008 follows a specific internal start-up procedure after

power is applied to the VDD pin. Table 6 describes the start-up

sequence.

If the device is to be synchronized to an external clock source, the

clock frequency must be stable prior to asserting the EN pin. The

device requires approximately 5ms to 10ms to check for specific

values stored in its internal memory. If the user has stored values

in memory, those values will be loaded. The device will then

check the status of all multi-mode pins and load the values

associated with the pin settings.

Once this process is completed, the device is ready to accept

commands via the I2C/SMBus interface and the device is ready

to be enabled. Once enabled, the device requires approximately

2ms before its output voltage may be allowed to start its ramp-

up process. If a soft-start delay period less than 2ms has been

configured (using PMBus commands), the device will default to a

2ms delay period. If a delay period greater than 2ms is

configured, the device will wait for the configured delay period

prior to starting to ramp its output.

After the delay period has expired, the output will begin to ramp

towards its target voltage according to the pre-configured

soft-start ramp time that has been set using the SS pin. It should

be noted that if the EN pin is tied to VDD, the device will still

require approx 5ms to 10ms before the output can begin its

ramp-up as described in Table 6.

Soft-start Delay and Ramp Times

It may be necessary to set a delay from when an enable signal is

received until the output voltage starts to ramp to its target

value. In addition, the designer may wish to precisely set the time

required for VOUT to ramp to its target value after the delay period

has expired. These features may be used as part of an overall

inrush current management strategy or to precisely control how

fast a load IC is turned on. The ZL2008 gives the system designer

several options for precisely and independently controlling both

the delay and ramp time periods.

The soft-start delay period begins when the EN pin is asserted

and ends when the delay time expires. The soft-start delay period

is set using the SS pin. Precise ramp delay timing reduces the

delay time variations but is only available when the appropriate

bit in the MISC_CONFIG register has been set. Please refer to

Application Note AN2033 for details.

The soft-start ramp timer enables a precisely controlled ramp to

the nominal VOUT value that begins once the delay period has

expired. The ramp-up is guaranteed monotonic and its slope may

be precisely set using the SS pin.

The soft-start delay and ramp times can be set to standard

values according to Table 7.

TABLE 5. DOSA Mode VOUT Settings

VOUT

(V)

RSET (k)

In series with 8.660k

 resistor

0.700

162

0.752

113

0.758

100

0.765

90.9

0.772

82.5

0.790

75.0

0.800

57.6

0.821

52.3

0.834

47.5

0.848

43.2

0.880

36.5

0.899

33.2

0.919

30.1

0.965

25.5

0.991

22.6

1.000

21.0

1.100

17.8

1.158

14.7

1.200

13.3

1.250

10.5

1.500

8.87

1.669

6.98

1.800

6.04

2.295

4.32

2.506

3.74

3.300

2.61

5.000

1.50

NOTE: (R0 = 110k

, R1 = RSET + 8.66k)

OUT

SET

6900





(EQ. 3)

8.66 kΩ

DOSA

MODULE

Rset

110 kΩ

FIGURE 12. RSET on a DOSA Module

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