ltc3586 Linear Technology Corporation, ltc3586 Datasheet - Page 25

• Manufacturer Part Number: ltc3586
• Description: High Ef? Ciency Usb Power Manager With Boost, Buck-boost And Dual Bucks
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
PowerPath CONTROLLER APPLICATIONS SECTION
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
switching regulator. To ensure that the USB specification is
strictly met, both components of input current should be
considered. The Electrical Characteristics table gives the
worst-case 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
+ V
An averaging capacitor 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 .
Choosing the PowerPath Inductor
Because the input voltage range and output voltage range
of the power path switching regulator are both fairly nar-
row, the LTC3586 was designed for a specifi c 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
TYPE
LPS4018
D53LC
DB318C
WE-TPC
Type M1
CDRH6D12
CDRH6D38
CLPROG
(μH)
/R
3.3
3.3
3.3
3.3
3.3
3.3
L
CLPPROG
MAX
2.26
1.55
1.95 0.065 4.8 × 4.8 × 1.8 Wurth Elektronik
2.2
2.2
3.5
I
(A)
DC
0.0625
0.034
0.070
0.020
MAX
DCR
0.08
OUT
(Ω)
• (h
CLPROG
and the quiescent current of the
3.9 × 3.9 × 1.7 Coilcraft
3.8 × 3.8 × 1.8
6.7 × 6.7 × 1.5
SIZE IN mm
(L × W × H)
5 × 5 × 3
7 × 7 × 4
+1).
MANUFACTURER
www.coilcraft.com
Toko
www.toko.com
www.we-online.com
Sumida
www.sumida.com
VBUS
= I
VBUSQ
V
The style and value of capacitors used with the LTC3586
determine several important parameters such as regulator
control-loop stability and input voltage ripple. Because
the LTC3586 uses a buck switching power supply from
V
frequency components. It is strongly recommended that a
low equivalent series resistance (ESR) multilayer ceramic
capacitor be used to bypass V
capacitors are not recommended because of their high ESR.
The value of the capacitor on V
amount of input ripple for a given load current. Increasing
the size of this capacitor will reduce the input ripple.
To prevent large V
conditions, it is also recommended that a ceramic capaci-
tor be used to bypass V
in the compensation of the switching regulator. At least
4μF of actual capacitance with low ESR are required on
V
performance and stability.
Multilayer ceramic chip capacitors typically have excep-
tional ESR performance. MLCCs combined with a tight
board layout and an unbroken ground plane will yield very
good performance and low EMI emissions.
There are several types of ceramic capacitors available
each having considerably different characteristics. For
example, X7R ceramic capacitors have the best voltage and
temperature stability. X5R ceramic capacitors have appar-
ently higher packing density but poorer performance over
their rated voltage and temperature ranges. Y5V ceramic
capacitors have the highest packing density, but must be
used with caution, because of their extreme non-linear
characteristic of capacitance verse voltage. The actual
in-circuit capacitance of a ceramic capacitor should be
measured with a small AC signal as is expected in-circuit.
Many vendors specify the capacitance verse voltage with
a 1V RMS AC test signal and as a result overstate the ca-
pacitance that the capacitor will present in the application.
Using similar operating conditions as the application, the
user must measure or request from the vendor the actual
capacitance to determine if the selected capacitor meets
the minimum capacitance that the application requires.
BUS
BUS
OUT
. Additional capacitance will improve load transient
and V
to V
OUT
OUT
, its input current waveform contains high
Bypass Capacitors
OUT
voltage steps during transient load
OUT
. The output capacitor is used
BUS
BUS
. Tantalum and aluminum
directly controls the
LTC3586
25
3586f