LTC3555 Linear Technology, LTC3555 Datasheet - Page 26

• Manufacturer Part Number: LTC3555
• Description: High Efficiency USB Power Manager + Triple Step-Down DC/DC
• Manufacturer: Linear Technology

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LTC3555
APPLICATIONS INFORMATION
Table 7. Recommended Inductors
INDUCTOR
TYPE
DE2818C
D312C
DE2812C
CDRH3D16
CDRH2D11
CLS4D09
SD3118
SD3112
SD12
SD10
LPS3015
*Typical DCR
General Purpose Switching Regulator Input/Output
Capacitor Selection
Low ESR (equivalent series resistance) MLCC capacitors
should be used at both switching regulator outputs as well
as at each switching regulator input supply (V
or X7R ceramic capacitors should be used because they
retain their capacitance over wider voltage and temperature
ranges than other ceramic types. A 10μF output capaci-
tor is suffi cient for most applications. For good transient
response and stability the output capacitor should retain
at least 4μF of capacitance over operating temperature and
bias voltage. Each switching regulator input supply should
be bypassed with a 1μF capacitor. Consult with capacitor
manufacturers for detailed information on their selection
and specifi cations of ceramic capacitors. Many manufac-
turers now offer very thin (<1mm tall) ceramic capacitors
26
(μH)
4.7
3.3
4.7
3.3
2.2
4.7
3.3
2.0
4.7
3.3
2.2
4.7
3.3
2.2
4.7
4.7
3.3
2.2
4.7
3.3
2.2
4.7
3.3
2.2
4.7
3.3
2.2
4.7
3.3
2.2
L
MAX
1.25
1.45
0.79
0.90
1.14
0.78
0.75
1.59
0.97
1.12
1.29
1.42
1.80
1.08
1.31
1.65
I
(A)
1.2
1.4
1.8
0.9
1.1
1.2
0.5
0.6
1.3
2.0
0.8
1.1
1.3
1.5
DC
0.067*
0.117*
0.104*
0.075*
0.153*
0.108*
0.091*
0.072
0.053
0.13*
0.10*
0.085
0.072
0.123
0.098
0.162
0.113
0.074
0.246
0.165
MAX
DCR
0.24
0.20
0.14
0.11
0.17
0.19
0.14
0.13
0.11
(Ω)
0.2
3.0 × 2.8 × 1.8
3.0 × 2.8 × 1.8
3.6 × 3.6 × 1.2
3.6 × 3.6 × 1.2
3.6 × 3.6 × 1.2
3.0 × 2.8 × 1.2
3.0 × 2.8 × 1.2
3.0 × 2.8 × 1.2
3.2 × 3.2 × 1.2
3.2 × 3.2 × 1.2
3.2 × 3.2 × 1.2
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.2
3.1 × 3.1 × 1.2
3.1 × 3.1 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.0
5.2 × 5.2 × 1.0
5.2 × 5.2 × 1.0
3.0 × 3.0 × 1.5
3.0 × 3.0 × 1.5
3.0 × 3.0 × 1.5
4.9 × 4.9 × 1
SIZE in mm
(L × W × H)
4 × 4 × 1.8
4 × 4 × 1.8
4 × 4 × 1.8
MANUFACTURER
Toko
www.toko.com
Sumida
www.sumida.com
Cooper
www.cooperet.com
Coil Craft
www.coilcraft.com
INX
). Only X5R
ideal for use in height-restricted designs. Table 8 shows a
list of several ceramic capacitor manufacturers.
Table 8. Recommended Ceramic Capacitor Manufacturers
AVX
Murata
Taiyo Yuden
Vishay Siliconix
TDK
Over-Programming the Battery Charger
The USB high power specifi cation allows for up to 2.5W to
be drawn from the USB port (5V × 500mA). The PowerPath
switching regulator transforms the voltage at V
above the voltage at BAT with high effi ciency, while limiting
power to less than the amount programmed at CLPROG.
In some cases the battery charger may be programmed
(with the PROG pin) to deliver the maximum safe charging
current without regard to the USB specifi cations. If there
is insuffi cient current available to charge the battery at the
programmed rate, the PowerPath regulator will reduce
charge current until the system load on V
and the V
battery charger for more current than is available will not
cause the average input current limit to be violated. It will
merely allow the battery charger to make use of all available
power to charge the battery as quickly as possible, and with
minimal power dissipation within the battery charger.
Alternate NTC Thermistors and Biasing
The LTC3555 provides temperature qualifi ed charging if
a grounded thermistor and a bias resistor are connected
to NTC. By using a bias resistor whose value is equal to
the room temperature resistance of the thermistor (R25)
the upper and lower temperatures are pre-programmed
to approximately 40°C and 0°C, respectively (assuming
a Vishay “Curve 1” thermistor).
The upper and lower temperature thresholds can be ad-
justed by either a modifi cation of the bias resistor value
or by adding a second adjustment resistor to the circuit.
If only the bias resistor is adjusted, then either the upper
or the lower threshold can be modifi ed but not both. The
other trip point will be determined by the characteristics
BUS
current limit is satisfi ed. Programming the
www.avxcorp.com
www.murata.com
www.t-yuden.com
www.vishay.com
www.tdk.com
OUT
is satisfi ed
BUS
to just
3555f