Linear Technology 1376A-A Quick Start Manual

DESCRIPTION
Demonstration circuits 1376A-A and 1376A-B are High
Efficiency USB Power Manager + Triple Step Down
DC/DC featuring the LTC3555-1 and LTC3555-3 respec-
tively. The LTC®3555-1/LTC3555-3 are highly integrated
power management and battery charger ICs for Li-
Ion/polymer battery applications. It includes a high effi-
ciency current limited switching PowerPath manager
with automatic charge current reduction, a battery
charger, an ideal diode and three general purpose syn-
chronous step-down switching regulators. Designed
specifically for USB applications, the LTC3555-
1/LTC3555-3's switching power manager automatically
limits input current to a maximum of either 100mA or
500mA for USB applications or 1A for AC-powered appli-
cations. Unlike linear PowerPath controllers, the
LTC3555-1/LTC3555-3's switching input stage transmits
PERFORMANCE SUMMARY
SYMBOL PARAMETER
VBUS Input Supply Range
VOUT VOUT Output Voltage
LDO3V3 LDO3V3 Output Voltage
V BAT Regulated Output Voltage
FLOAT
I Constant Current Mode Charge Current
BAT
VOUT1 VOUT1 Output Voltage
VOUT2 VOUT2 Output Voltage
VOUT3 VOUT3 Output Voltage
QUICK START PROCEDURE
Demonstration circuits 1376A-A and 1376A-B are easy
to set up to evaluate the performance of the LTC3555-1
and LTC3555-3. These circuits are best evaluated using
a Li-Ion or Li-Polymer battery. When using a battery
simulator for evaluation, oscillations must be verified
with a real battery at the same conditions because it is
Demo Circuit1376A-A/-B
LTC3555-1 AND LTC3555-3
LTC3555-1 and LTC3555-3
High Efficiency USB Power Manager
+ Triple Step Down DC/DC
nearly all of the 2.5W available from the USB port to the
system load with minimal power wasted as heat. This
feature allows the LTC3555-1/LTC3555-3 to provide
more power to the application and eases the constraint
of thermal budgeting in small spaces. Two of the three
general purpose switching regulators can provide up to
400mA and the third can deliver 1A. The entire product
can be started from an external push button and subse-
quently controlled via I
available in the 28-pin (4mm × 5mm × 0.75mm) QFN
surface mount package.
Design files for this circuit board are available. Call
the LTC factory.
L
, LTC, LTM, LT, Burst Mode, are registered trademarks of Linear Technology Corporation.
PowerPath are trademarks of Linear Technology Corporation. Other product names may be
trademarks of the companies that manufacture the products.
Specifications are at T
A
CONDITIONS
Mode and load dependant
Load and VOUT dependant
LTC3555-1
LTC3555-3
R = 2KΩ
PROG
Servo Voltage = 0.8
Servo Voltage = 0.8
difficult to match the impedance of a real battery. Ca-
pacitor C15 in combination with R9, R10, and R11 were
added to simulate the low impedance of a real battery.
It will allow proper operation of the demo circuit with or
without a battery, or a battery simulator consisting of a
power supply in parallel with a 3.6 Ohm resistor.
QUICK START GUIDE
2
C. The LTC3555-1/LTC3555-3 is
= 25°C
MIN
4.35
3.4 Bat + 0.3
4.179
4.079
460
TYP MAX UNITS
5.5 V
4.7 V
3.3 V
4.2 4.221 V
4.1 4.121 V
511 532 mA
3.3 V
3.0 V
1.5 V
1