LTC3577EUFF#PBF Linear Technology, LTC3577EUFF#PBF Datasheet - Page 20

• 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
LTC3577/LTC3577-1
PowerPath OPERATION
Introduction
The LTC3577 is a highly integrated power management
IC that features:
Designed specifi cally for USB applications, the PowerPath
controller incorporates a precision input current limit
which communicates with the battery charger to ensure
20
– PowerPath controller
– Battery charger
– Ideal diode
– Input overvoltage protection
– Pushbutton controller
– Three step-down switching regulators
– High voltage buck regulator V
– Two low dropout linear regulators
– 40V LED backlight controller
FROM
USB
FROM AC ADAPTER (OR HIGH VOLTAGE BUCK OUTPUT)
40
4
WALL
V
BUS
(FALLING)
(RISING)
4.3V
3.2V
+
–
75mV (RISING)
25mV (FALLING)
–
+
+
–
C
controller
Figure 1. Simplifi ed PowerPath Block Diagram
USB CURRENT LIMIT
FOR HIGH VOLTAGE BUCK REGS
LT3480, LT3481 OR LT3505
ENABLE
OPTIONAL CONTROL
42
V
C
CONSTANT CURRENT
CONSTANT VOLTAGE
BATTERY CHARGER
that input current does not violate the USB average input
current specifi cation. The ideal diode from BAT to V
guarantees that ample power is always available to V
even if there is insuffi cient or absent power at V
LTC3577 also has the ability to receive power from a wall
adapter or other non-current-limited power source. Such
a power supply can be connected to the V
LTC3577 through an external device such as a power
Schottky or FET as shown in Figure 1. The LTC3577 has
the unique ability to use the output, which is powered by
an external supply, to charge the battery while provid-
ing power to the load. A comparator on the WALL pin is
confi gured to detect the presence of the wall adapter and
shut off the connection to the USB. This prevents reverse
conduction from V
ent. The LTC3577 provides a V
used to drive the V
switching regulator such as the LT3480, LT3653 or LT3505
to provide power to the V
adjusts the regulation point of the switching regulator to
V
BAT
OUT
DIODE
IDEAL
–
+
OUT
15mV
C
+
–
pin of an external high voltage buck
to V
IDGATE
OUT
ACPR
BUS
V
BAT
OUT
3577 F01
pin. The V
when a wall adapter is pres-
41
39
37
38
C
output pin which can be
+
C
Li-Ion
control circuitry
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
SYSTEM
OUT
LOAD
pin of the
BUS
. The
3577fa
OUT
OUT