LTC3576EUFE#PBF Linear Technology, LTC3576EUFE#PBF Datasheet - Page 19

• Manufacturer Part Number: LTC3576EUFE#PBF
• Description: IC POWER MANAGER W/USB OTG 38QFN
• Manufacturer: Linear Technology

Specifications of LTC3576EUFE#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: 38-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

Bidirectional PowerPath Switching Regulator—
Step-Down Mode
The power delivered from V
a 2.25MHz constant frequency bidirectional switching
regulator operating in step-down mode. V
combination of the external load (step-down switching
regulators 1, 2 and 3) and the battery charger. To meet the
maximum USB load specifi cation, the switching regulator
contains a measurement and control system that ensures
that the average input current remains below the level
programmed at CLPROG.
If the combined load does not cause the switching regu-
lator to reach the programmed input current limit, V
will track approximately 0.3V above the battery voltage.
By keeping the voltage across the battery charger at this
low level, power lost to the battery charger is minimized.
Figure 1 shows the power fl ow in step-down mode.
OPERATION
OR WALL
ADAPTER
TO USB
TO AUTOMOTIVE,
FIREWIRE, ETC.
35
34
6
5
1
I
OVSENS
OVGATE
V
V
SWITCH
CLPROG
BUS
BUS
1.18V
Figure 1. PowerPath Block Diagram—Power Available from USB/Wall Adapter
/N
AVERAGE V
CURRENT LIMIT
CONTROLLER
BUS
–
+
5V
CONTROLLER
OVERVOLTAGE PROTECTION
2
VOLTAGE
BUS
V
BUS
to V
–
+
INPUT
–
+
OUT
GATE DRIVE
+ –
PWM AND
is controlled by
OUT
6V
V
CONTROLLER
drives the
OUT
VOLTAGE
26
–
+
+
V
C
OUT
V
V
3.6V
IN
C
HIGH VOLTAGE
STEP-DOWN
REGULATOR
SWITCHING
0.3V
+ –
CONSTANT CURRENT
CONSTANT VOLTAGE
BATTERY CHARGER
If the combined external load plus battery charge current
is large enough to cause the switching regulator to reach
the programmed input current limit, the battery charger
will reduce its charge current by precisely the amount
necessary to enable the external load to be satisfi ed. Even
if the battery charge current is programmed to exceed the
allowable USB current, the USB specifi cation for average
input current will not be violated; the battery charger will
reduce its current as needed. Furthermore, if the load cur-
rent at V
load current will be drawn from the battery via the ideal
diode(s) even when the battery charger is enabled.
The current out of CLPROG is a precise fraction of the V
current. When a programming resistor and an averaging
capacitor are connected from CLPROG to GND, the volt-
age on CLPROG represents the average input current of
the switching regulator. As the input current approaches
the programmed limit, CLPROG reaches 1.18V and power
delivered by the switching regulator is held constant.
SW
FB
–
+
+
OUT
Bat-Track HV CONTROL
V
3.6V
BAT + 0.3V
OUT
OmV
IDEAL
DIODE
15mV
exceeds the programmed power from V
27
LTC3576/LTC3576-1
–
+
WALL
4.3V
+
–
–
+
USB INPUT
BATTERY POWER
HV INPUT
IDGATE
ACPR
V
OUT
BAT
SW
28
36
33
31
32
3576 F01
+
SINGLE CELL
Li-Ion
OPTIONAL EXTERNAL
IDEAL DIODE PMOS
3.5V TO
(BAT + 0.3V)
TO SYSTEM LOAD
19
BUS
3576fb
BUS
,