LTC3675 Datasheet, PDF (27/36 Pages) Linear Technology – 7-Channel Confi gurable High Power PMIC

LTC3675
APPLICATIONS INFORMATION
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.
The boost regulator can be programmed via I²C. To pro-
gram the boost regulator, use sub-address 05h. The bit
format is explained in Table 9.
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.
When enabled via pin, the contents of the I²C register program its functionality.
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 7. Recommended Inductors for 2A Combined Buck Regulator
PART NUMBER
L(μH)
MAX I_DC (A)
MAX DCR (mΩ)
XFL4022-222
2.2
3.5
21.35
LPS6225-222
2.2
4
45
FDV0530-2R2
2.2
5.3
17.3
SIZE IN mm (L × W × H)
4×4×2
6 × 6 × 2.5
6.2 × 5.8 × 3
MANUFACTURER
Coilcraft
www.coilcraft.com
Coilcraft
www.coilcraft.com
Toko
www.toko.com
Table 8. Recommended Inductors for Boost Regulator and Buck-Boost Regulator
PART NUMBER
L(μH)
MAX I_DC (A)
MAX DCR (mΩ) SIZE IN mm (L × W × H)
XFL4022-222
2.2
3.5
21.35
4×4×2
LTF5022-2R2
2.2
3.2
36
5 × 5.2 × 2.2
MANUFACTURER
Coilcraft
www.coilcraft.com
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.
3675f
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