ZL6105ALAF datasheet(16/35 Pages) INTERSIL

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ZL6105

FN6906.5

December 19, 2013

The switching frequency can also be set to any value between

200kHz and 1.33MHz using the I2C/SMBus interface. The available

frequencies below 1.4MHz are defined by fSW = 8MHz/N, where the

whole number N is 6

≤ N ≤ 40. See Application Note AN2033 for

details.

If a value other than fSW = 8MHz/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 810kHz is entered, the device will select 800kHz (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 11. The difference is due to hardware quantization.

Power Train Component Selection

The ZL6105 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 12 must be known.

DESIGN GOAL TRADE-OFFS

The design of the buck power stage requires several

compromises among size, efficiency, and cost. The inductor core

loss increases with frequency, so there is a trade-off between a

small output filter made possible by a higher switching frequency

and getting better power supply efficiency. Size can be decreased

Logic

high

SYNC

200 kHz – 1.33MHz

SYNC

200kHz – 1.4MHz

N/C

SYNC

200kHz – 1.4MHz

A) SYNC = output

B) SYNC = input

N/C

SYNC

RSYNC

N/C

SYNC

Logic

high

Logic

low

Open

C) SYNC = Auto Detect

FIGURE 10. SYNC PIN CONFIGURATIONS

TABLE 11. SWITCHING FREQUENCY RESISTOR SETTINGS

RSYNC

Ω)

fSW

(kHz)

RSYNC

Ω)

fSW

(kHz)

200

26.1

533

222

28.7

571

12.1

242

31.6

615

13.3

267

34.8

727

14.7

296

38.3

800

16.2

320

46.4

889

17.8

364

51.1

1000

19.6

400

56.2

1143

21.5

421

68.1

1333

23.7

471

TABLE 12. POWER SUPPLY REQUIREMENTS

PARAMETER

RANGE

EXAMPLE

VALUE

Input Voltage (VIN)

3V to 14V

12V

Output Voltage (VOUT)

0.6V to 5.0V

1.2V

Output Current (IOUT)

0A to ~25A

20A

Output Voltage Ripple

(VORIP)

<3% of VOUT

1% of VOUT

Output Load Step (IOSTEP)<IO

50% of IO

Output Load Step Rate

10A/µs

Output Deviation Due to Load Step

±50mV

Maximum PCB Temp.

+120°C

+85°C

Desired Efficiency

85%

Other Considerations

Various

Optimize for

small size

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