LTC3589 datasheet(23/44 Pages) LINER

23 / 44 page

LTC3589

3589p

The value of R1 plays a role in setting the dynamics of

the buck-boost voltage mode control loop. In general, a

larger value for R1 will increase stability but reduce the

speed of the transient response. A good starting point is

to choose R1 equal to 1MΩ and calculate the value of R2

needed to set the target output voltage. If a large output

capacitor is used, the bandwidth of the converter is reduced

and R1 may be reduced to improve transient response. If

a large inductor or small output capacitor is used then a

larger R1 should be used to bring the loop toward more

stable operation.

Modes of Operations

Table 9 shows the I2C command registers used to control

the operating modes of the LTC3589 buck-boost converter.

When command register SCR1 bit 6 is LOW, the LTC3589

buck-boost switching regulator operates in a ﬁxed fre-

quency pulse width modulation mode using voltage mode

feedback control. A proprietary switching algorithm allows

the converter to transition between buck, buck-boost, and

boost modes without discontinuity in inductor current or

loop characteristics. The switch topology is shown in the

application circuit in Figure 4.

Table 9. Buck-Boost Command Register Settings

COMMAND

VALUE

SETTING

SCR1[6]

Continuous Mode

Burst Mode Operation

OVEN[3]

Disable

Enable

SCR2[3]

Wait for Output Below 300mV Before Enable

Enable Immediately

* Denotes Default Power-On Value

When the input voltage is signiﬁcantly greater than the

output voltage, the buck-boost converter operates in

buck mode. Switch D turns on continuously and switch C

remains off. Switches A and B are pulse width modulated

to produce the required duty cycle to support the output

OPERATION

Table 8. Inductors for Step-Down Switching Regulators 2 and 3

MANUFACTURERS

PART NUMBER

VALUE

(μH)

DCR (Ω)

MAX DC

CURRENT (A)

SIZE (mm) W × L × H

Coilcraft

XPL4020-102ML

XPL4020-152ML

XPL4020-472ML

1.0

1.5

4.7

0.029

0.036

0.130

4.00

3.60

1.90

4.2 × 4.2 × 2.0

Cooper

SD14-1R2-R

SD14-3R2-R

SD25-3R3-R

1.2

3.2

3.3

0.034

0.066

0.038

3.35

2.00

2.21

5.2 × 5.2 × 1.45

4.8 × 4.8 × 2.5

Sumida

CDRH5D16NP-4R7N

CDRH38D16RHPNP-3R3M

4.7

3.3

0.064

0.059

2.05

1.46

5.6 × 5.6 × 1.8

4.2 × 4.2 × 1.8

TDK

VLF5014ST-2R2N2R3

VLCF5020T-2R7N2R2-1

VLCF5020T-3R3N2R0-1

2.2

2.7

3.3

0.073

0.083

0.096

2.3

2.2

4.8 × 4.6 × 1.4

5.0 × 5.0 × 2.0

TOKO

1124BS-2R4N

1124BS-3R3N

2.4

3.3

0.065

0.074

2.30

2.10

4.5 × 4.7 × 1.8

Tokin

H-DI-0520-3R3

H-DI-0520-4R7

H-DI-0630-3R8

H-DI-0630-4R7

3.3

4.7

3.8

4.7

0.062

0.090

0.040

0.043

2.00

1.80

2.00

1.90

5.3 × 5.3 × 2.0

6.3 × 6.3 × 3.0

Wurth

744043004

744052002

7440530047

744042003

7440430022

4.7

2.5

4.7

3.3

2.2

0.052

0.030

0.055

0.023

1.55

2.4

1.95

2.5

5.0 × 5.0 × 3.0

5.8 × 5.8 × 1.8

5.8 × 5.8 × 2.8

4.8 × 4.8 × 1.8

4.8 × 4.8 × 2.8

LTC3589 Datasheet(PDF) 23 Page - Linear Technology

LTC3589 Datasheet(HTML) 23 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL