LTC3566 Datasheet, PDF (19/28 Pages) Linear Technology – High Effi ciency USB Power Manager Plus 1A Buck-Boost Converter

LTC3566
APPLICATIONS INFORMATION
CLPROG Resistor and Capacitor
As described in the High Efficiency Switching PowerPath
Controller section, the resistor on the CLPROG pin deter-
mines the average input current limit when the switching
regulator is set to either the 1x mode (USB 100mA), the
5x mode (USB 500mA) or the 10x mode. The input cur-
rent will be comprised of two components, the current
that is used to drive V_OUT and the quiescent current of the
switching regulator. To ensure that the USB specification
is strictly met, both components of input current should
be considered. The Electrical Characteristics table gives
values for quiescent currents in either setting as well as
current limit programming accuracy. To get as close to
the 500mA or 100mA specifications as possible, a 1%
resistor should be used. Recall that I_VBUS = I_VBUSQ +
V_CLPROG/R_CLPROG • (h_CLPROG + 1).
An averaging capacitor or an R-C combination is required
in parallel with the CLPROG resistor so that the switching
regulator can determine the average input current. This
network also provides the dominant pole for the feedback
loop when current limit is reached. To ensure stability, the
capacitor on CLPROG should be 0.1μF or larger.
Choosing the PowerPath Inductor
Because the input voltage range and output voltage range
of the PowerPath switching regulator are both fairly nar-
row, the LTC3566 was designed for a specific inductance
value of 3.3μH. Some inductors which may be suitable
for this application are listed in Table 4.
Table 4. Recommended Inductors for PowerPath Controller
INDUCTOR L MAX MAX
TYPE
(μH) IDC DCR
(A) (Ω)
SIZE IN mm MANUFACTURER
(L × W × H)
LPS4018
3.3 2.2 0.08 3.9 × 3.9 × 1.7 CoilCraft
www.coilcraft.
com
D53LC
DB318C
3.3 2.26 0.034 5.0 × 5.0 × 3.0 Toko
3.3 1.55 0.070 3.8 × 3.8 × 1.8 www.toko.com
WE-TPC
Type M1
3.3 1.95 0.065 4.8 × 4.8 × 1.8 Würth Elektronik
www.we-online.
com
CDRH6D12 3.3 2.2 0.0625 6.7 × 6.7 × 1.5 Sumida
CDRH6D38 3.3 3.5 0.020 7.0 × 7.0 × 4.0 www.sumida.com
3566fa
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