LTC3567 Datasheet, PDF (22/28 Pages) Linear Technology – High Effi ciency USB Power Manager Plus 1A Buck-Boost Converter with I2C Control

LTC3567
APPLICATIONS INFORMATION
Table 7. Recommended Inductors for Buck-Boost Regulator
MAX MAX
INDUCTOR L I_DC DCR
TYPE (μH) (A) (Ω)
SIZE IN mm
(L × W × H) MANUFACTURER
LPS4018 3.3 2.2 0.08 3.9 × 3.9 × 1.7 Coilcraft
2.2 2.5 0.07 3.9 × 3.9 × 1.7 www.coilcraft.com
D53LC
2.0 3.25 0.02 5.0 × 5.0 × 3.0 Toko
www.toko.com
7440430022 2.2 2.5 0.028 4.8 × 4.8 × 2.8 Würth-Elektronik
www.we-online.com
CDRH4D22/ 2.2 2.4 0.044 4.7 × 4.7 × 2.4 Sumida
HP
www.sumida.com
SD14
2.0 2.56 0.045 5.2 × 5.2 × 1.45 Cooper
www.cooper.com
Buck-Boost Regulator Input/Output Capacitor
Selection
Low ESR MLCC capacitors should also be used at both
the buck-boost regulator output (V_OUT1) and the buck-
boost regulator input supply (V_IN1). Only X5R or X7R
ceramic capacitors should be used because they retain
their capacitance over wider voltage and temperature
ranges than other ceramic types. A 22μF output capaci-
tor is sufficient for most applications. The buck-boost
regulator input supply should be bypassed with a 2.2μF
capacitor. Consult with capacitor manufacturers for de-
tailed information on their selection and specifications of
ceramic capacitors. Many manufacturers now offer very
thin (<1mm tall) ceramic capacitors ideal for use in height
restricted designs. Table 8 shows a list of several ceramic
capacitor manufacturers.
Table 8. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
WEBSITE
AVX
www.avxcorp.com
Murata
www.murata.com
Taiyo Yuden
www.t-yuden.com
Vishay Siliconix
www.vishay.com
TDK
www.tdk.com
Over-Programming the Battery Charger
The USB high power specification allows for up to 2.5W to
be drawn from the USB port (5V × 500mA). The PowerPath
switching regulator transforms the voltage at V_BUS to just
above the voltage at BAT with high efficiency, while limiting
power to less than the amount programmed at CLPROG.
22
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 specifications. If there
is insufficient current available to charge the battery at the
programmed rate, the PowerPath regulator will reduce
charge current until the system load on V_OUT is satisfied
and the V_BUS current limit is satisfied. Programming the
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 LTC3567 provides temperature qualified 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 modification 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 modified but not both. The
other trip point will be determined by the characteristics
of the thermistor. Using the bias resistor in addition to an
adjustment resistor, both the upper and the lower tem-
perature trip points can be independently programmed
with the constraint that the difference between the upper
and lower temperature thresholds cannot decrease. Ex-
amples of each technique follow.
NTC thermistors have temperature characteristics which
are indicated on resistance-temperature conversion tables.
The Vishay-Dale thermistor NTHS0603N011-N1003F, used
in the following examples, has a nominal value of 100k
and follows the Vishay “Curve 1” resistance-temperature
characteristic.
In the explanation below, the following notation is used.
R25 = Value of the thermistor at 25°C
R_NTC|COLD = Value of thermistor at the cold trip point
3567f