LTC3589 Linear Technology, LTC3589 Datasheet - Page 23

• Manufacturer Part Number: LTC3589
• Description: 8-Output Regulator
• Manufacturer: Linear Technology

OPERATION
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 I
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 fi xed fre-
quency pulse width modulation mode using voltage mode
feedback control. A proprietary switching algorithm allows
Table 8. Inductors for Step-Down Switching Regulators 2 and 3
MANUFACTURERS
Coilcraft
Cooper
Sumida
TDK
TOKO
Tokin
Wurth
2
C command registers used to control
CDRH38D16RHPNP-3R3M
VLCF5020T-2R7N2R2-1
VLCF5020T-3R3N2R0-1
VLF5014ST-2R2N2R3
CDRH5D16NP-4R7N
XPL4020-472ML
XPL4020-102ML
XPL4020-152ML
H-DI-0520-3R3
H-DI-0520-4R7
H-DI-0630-3R8
H-DI-0630-4R7
PART NUMBER
1124BS-2R4N
1124BS-3R3N
SD25-3R3-R
7440430022
SD14-1R2-R
SD14-3R2-R
7440530047
744043004
744052002
744042003
VALUE
(μH)
3.2
3.3
3.3
2.2
3.3
3.3
3.3
3.8
2.5
3.3
2.2
1.0
1.5
4.7
1.2
4.7
2.7
2.4
4.7
4.7
4.7
4.7
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
REGISTER[BIT]
SCR1[6]
OVEN[3]
SCR2[3]
* Denotes Default Power-On Value
When the input voltage is signifi cantly 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
DCR (Ω)
0.029
0.036
0.034
0.066
0.038
0.064
0.059
0.083
0.096
0.065
0.062
0.090
0.040
0.043
0.052
0.030
0.030
0.055
0.023
0.130
0.073
0.074
CURRENT (A)
MAX DC
VALUE
4.00
3.60
3.35
2.00
2.21
2.05
2.30
2.00
2.00
1.90
1.46
2.10
1.80
1.90
1.55
1.95
2.3
2.2
2.4
2.4
2.5
2
0*
1
0*
1
0*
1
SETTING
Continuous Mode
Burst Mode Operation
Disable
Enable
Wait for Output Below 300mV Before Enable
Enable Immediately
SIZE (mm) W × L × H
5.2 × 5.2 × 1.45
5.2 × 5.2 × 1.45
4.2 × 4.2 × 2.0
4.2 × 4.2 × 2.0
4.2 × 4.2 × 2.0
6.3 × 6.3 × 3.0
6.3 × 6.3 × 3.0
4.8 × 4.8 × 2.5
5.6 × 5.6 × 1.8
4.2 × 4.2 × 1.8
4.8 × 4.6 × 1.4
5.0 × 5.0 × 2.0
5.0 × 5.0 × 2.0
4.5 × 4.7 × 1.8
4.5 × 4.7 × 1.8
5.3 × 5.3 × 2.0
5.3 × 5.3 × 2.0
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
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LTC3589
23
3589p