LTC3577EUFF#PBF Linear Technology, LTC3577EUFF#PBF Datasheet - Page 21

• Manufacturer Part Number: LTC3577EUFF#PBF
• Description: IC PWR MANAGEMENT HANDHELD 44QFN
• Manufacturer: Linear Technology

Specifications of LTC3577EUFF#PBF

• Applications: Handheld/Mobile Devices
• Voltage - Supply: 4.35 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 44-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

OPERATION
a small voltage above the BAT pin voltage. This control
method provides a high input voltage, high effi ciency
battery charger and PowerPath function.
The LTC3577 also includes a pushbutton input to control
the three synchronous step-down switching regulators
and system reset. The three 2.25MHz constant frequency
current mode step-down switching regulators provide
500mA, 500mA and 800mA each and support 100% duty
cycle operation as well as Burst Mode operation for high
effi ciency at light load. No external compensation compo-
nents are required for the switching regulators.
The onboard LED backlight boost circuitry can drive up
to 10 series LEDs and includes versatile digital dimming
via the I
low dropout (LDO) linear regulators.
All regulators can be programmed for a minimum output
voltage of 0.8V and can be used to power a microcon-
troller core, microcontroller I/O, memory or other logic
circuitry.
USB PowerPath Controller
The input current limit and charge control circuits of the
LTC3577 are designed to limit input current as well as
control battery charge current as a function of I
V
step-down switching regulators, two LDOs, LED backlight
and the battery charger.
If the combined load does not exceed the programmed
input current limit, V
an internal 200mΩ P-channel MOSFET. If the combined
load at V
the battery charger will reduce its charge current by the
amount necessary to enable the external load to be satisfi ed
while maintaining the programmed input current. Even if
the battery charge current is set to exceed the allowable
USB current, the average input current USB specifi cation
will not be violated. Furthermore, load current at V
will always be prioritized and only excess available cur-
rent will be used to charge the battery. The current out
of the CLPROG pin is a fraction (1/h
OUT
drives the combination of the external load, the three
2
OUT
C input. The I
exceeds the programmed input current limit,
OUT
2
C input also controls two 150mA
will be connected to V
CLPROG
) of the V
BUS
through
VOUT
OUT
BUS
.
current. When a programming resistor is connected from
CLPROG to GND, the voltage on CLPROG represents the
input current:
where I
acteristics table.
The input current limit is programmed by the I
I
current to one of several possible settings as well as be
deactivated (USB suspend). The input current limit will be
set by the appropriate servo voltage and the resistor on
CLPROG according to the following expression:
Under worst-case conditions, the USB specifi cation for
average input current will not be violated with an R
resistor of 2.1k or greater. Table 1 shows the available
settings for the I
Table 1. Controlled Input Current Limit
Notice that when I
current limit is set to a higher current limit for increased
charging and current availability at V
typically used when there is a higher power, non-USB
source available at the V
LIM1
I
I
I
I
VBUS
VBUS
VBUS
VBUS
pins. The LTC3577 can be confi gured to limit input
BUSQ
I
LIM1
0
0
1
1
=I
=I
=I
=I
BUSQ
BUSQ
BUSQ
BUSQ
and h
LTC3577/LTC3577-1
LIM0
+
+
+
+
CLPROG
LIM0
R
R
R
R
V
CLPROG
CLPROG
CLPROG
CLPROG
CLPROG
0.2V
and I
2V
1V
is high and I
BUS
are given in the Electrical Char-
LIM1
I
LIM0
0
1
0
1
• h
• h
• h
• h
pin.
pins:
CLPROG
CLPROG
CLPROG
CLPROG
LIM1
OUT
(
(
(
1x Mode
5x Mode
10x Mode
is low, the input
. This mode is
100mA (1x)
500mA (5x)
I
1A (10x)
Suspend
BUS(LIM)
LIM0
21
)
CLPROG
)
)
3577fa
and