LTC3675

27

3675fa

APPLICATIONS INFORMATION

Table 7. Recommended Inductors for 2A Combined Buck Regulator

PART NUMBER

L(μH)

MAX DCR (mΩ)

SIZE IN mm (L

× W × H)

MANUFACTURER

XFL4022-222

2.2

3.5

21.35

4

× 4 × 2

Coilcraft

www.coilcraft.com

LPS6225-222

2.2

4

45

6

× 6 × 2.5

Coilcraft

www.coilcraft.com

FDV0530-2R2

2.2

5.3

17.3

6.2

× 5.8 × 3

Toko

www.toko.com

Table 6. Buck Regulator Program Register Bit Format

Bit7

Enable

Default is '0' which disables the part. A buck regulator can also be enabled via its enable pin.

Bit6

OUT_Hi-Z

Default is ‘1’ in which the SW node remains in a high impedance state when the regulator is in shutdown.

A ‘0’ pulls the SW node to GND through a 10k resistor.

Bit5

Mode

Default is ‘1’ which is Burst Mode operation. A ‘0’ programs the regulator to operate in pulse-skipping mode.

Bit4

Slow Edge

This bit controls the slew rate of the switch node. Default is '0' which enables the switch node to slew at a

faster rate, than if the bit were programmed a '1'.

Bit3(DAC3)

Bit2(DAC2)

Bit1(DAC1)

Bit0(DAC0)

DAC Control

These bits are used to program the feedback regulation voltage. Default is '1111' which programs a full-scale

voltage of 800mV. Bits '0000' program the lowest feedback regulation of 425mV. A LSB (DAC0) has a bit

weight of 25mV.

Table 8. Recommended Inductors for Boost Regulator and Buck-Boost Regulator

PART NUMBER

L(μH)

MAX DCR (mΩ)

SIZE IN mm (L

× W × H)

MANUFACTURER

XFL4022-222

2.2

3.5

21.35

4

×4 × 2

Coilcraft

www.coilcraft.com

LTF5022-2R2

2.2

3.2

36

5

× 5.2 × 2.2

TDK

www.tdk.com

Table 9. Boost Regulator Program Register Bit Format

Bit7

Enable

Default is ‘0’ which disables the boost.

Bit6

x

Unused

Bit5

Mode

Mode = 0 is PWM mode, Mode = 1 is Burst Mode operation

Bit4

Slow Edge

This bit controls the slew rate of the switch node. Default is ‘0’ which enables the switch node

to slew at a faster rate than if the bit were programmed a ‘1.’

Bit3(DAC3)

Bit2(DAC2)

Bit1(DAC1)

Bit0(DAC0)

DAC Control

These bits are used to program the feedback regulation voltage. Default is ‘1111’ which

programs a full-scale voltage of 800mV. Bits ‘0000’ program the lowest feedback regulation of

425mV. A LSB (DAC0) has a bit weight of 25mV.

a 47μF capacitor for a 2A combined buck regulator and

22μF for a 1A combined buck regulator. Refer to “Capaci-

tor Selection” in the Applications Information section for

details on selecting a proper capacitor.

Boost Regulator

The boost regulator is designed to be used with a 2.2μH

inductor. Table 8 provides a list of recommended inductors.

The input supply needs to be decoupled with a 10μF

capacitor while the output needs to be decoupled with

two 22μF capacitors. Refer to Capacitor Selection in the

Applications Information section for details on selecting

a proper capacitor.

gram the boost regulator, use sub-address 05h. The bit

format is explained in Table 9.