ZL2008 datasheet(21/47 Pages) INTERSIL

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ZL2008

Data Sheet Revision 2/19/2009

www.intersil.com

Table 15. Switching Frequency Resistor Settings

RSYNC

fSW

RSYNC

fSW

10 kΩ

200 kHz

26.1 kΩ

533 kHz

11 kΩ

222 kHz

28.7 kΩ

571 kHz

12.1 kΩ

242 kHz

31.6 kΩ

615 kHz

13.3 kΩ

267 kHz

34.8 kΩ

727 kHz

14.7 kΩ

296 kHz

38.3 kΩ

800 kHz

16.2 kΩ

320 kHz

46.4 kΩ

889 kHz

17.8 kΩ

364 kHz

51.1 kΩ

1000 kHz

19.6 kΩ

400 kHz

56.2 kΩ

1143 kHz

21.5 kΩ

421 kHz

68.1 kΩ

1333 kHz

23.7 kΩ

471 kHz

The switching frequency can also be set to any value

between 200 kHz and 1.33 MHz using the I2C/SMBus

interface. The available frequencies below 1.4 MHz are

defined by fSW = 8 MHz/N, where the whole number N

is 6 ≤ N ≤ 40. See Application Note AN33 for details.

If a value other than fSW = 8 MHz/N is entered using a

PMBus command, the internal circuitry will select the

valid switching frequency value that is closest to the

entered value. For example, if 810 kHz is entered, the

device will select 800 kHz (N=10).

When multiple Zilker Labs devices are used together,

connecting the SYNC pins together will force all

devices to synchronize with each other. The CFG1 pin

of one device must set its SYNC pin as an output and

the remaining devices must have their SYNC pins set

as Auto Detect.

Note: The switching frequency read back using the

appropriate PMBus command will differ slightly from

the selected values in Table 15. The difference is due

to hardware quantization.

5.8 Power Train Component Selection

The ZL2008 is a synchronous buck converter that uses

external MOSFETs, inductor and capacitors to perform

the power conversion process. The proper selection of

the external components is critical for optimized

performance.

To select the appropriate external components for the

desired

performance

goals,

the

power

supply

requirements listed in Table 16 must be known.

Figure 15. SYNC Pin Configurations

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