ltc3576 Linear Technology Corporation, ltc3576 Datasheet - Page 21

• Manufacturer Part Number: ltc3576
• Description: Switching Power Manager With Usb On-the-go + Triple Step-down Dc/dcs
• Manufacturer: Linear Technology Corporation

high voltage switching regulator. As a step-up converter,
the bidirectional switching regulator produces 5V on
V
on-the-go can be enabled by either the external control
pin, ENOTG, or via I
in step-up mode.
An undervoltage lockout circuit monitors V
vents step-up conversion until V
prevent backdriving of V
the V
conversion if V
mode is enabled. The switching regulator is also designed
to allow true output disconnect by eliminating body diode
conduction of the internal PMOS switch. This allows V
to go to zero volts during a short-circuit condition or while
shut down, drawing zero current from V
The voltage regulation loop is compensated by the capaci-
tance on V
Additional capacitance beyond this value will improve
OPERATION
TO USB
CABLE
BUS
BUS
and is capable of delivering at least 500mA. USB
TO AUTOMOTIVE,
FIREWIRE, ETC.
undervoltage lockout circuit prevents step-up
BUS
. A 4.7μF MLCC is required for loop stability.
BUS
35
34
6
5
1
is greater than 4.3V at the time step-up
I
OVSENS
OVGATE
V
V
SWITCH
CLPROG
BUS
BUS
2
1.15V
C. Figure 3 shows the power fl ow
AVERAGE V
/N
BUS
CURRENT LIMIT
CONTROLLER
–
+
when input power is available,
5V
OVERVOLTAGE PROTECTION
2
CONTROLLER
BUS
VOLTAGE
V
BUS
OUTPUT
–
+
OUT
–
+
Figure 3. PowerPath Block Diagram—USB On-the-Go
+ –
GATE DRIVE
rises above 2.8V. To
PWM AND
OUT
6V
OUT
.
V
CONTROLLER
26
OUT
and pre-
V
VOLTAGE
C
–
+
+
V
V
BUS
3.6V
IN
C
HIGH VOLTAGE
STEP-DOWN
REGULATOR
SWITCHING
0.3V
+ –
CONSTANT CURRENT
CONSTANT VOLTAGE
BATTERY CHARGER
transient response. The V
3% load regulation up to an output current of 500mA. At
light loads, the switching regulator goes into Burst Mode
operation. The regulator will deliver power to V
reaches 5.1V after which the NMOS and PMOS switches
shut off. The regulator delivers power again to V
it falls below 5.1V.
The switching regulator features both peak inductor and
average output current limit. The peak current mode
architecture limits peak inductor current on a cycle-by-
cycle basis. The peak current limit is equal to V
a maximum of 1.8A so that in the event of a sudden short
circuit, the current limit will fold back to a lower value.
In step-up mode, the voltage on CLPROG represents the
average output current of the switching regulator when
a programming resistor and an averaging capacitor are
connected from CLPROG to GND. With a 3.01k resistor
on CLPROG, the bidirectional switching regulator has an
output current limit of 680mA. As the output current ap-
proaches this limit CLPROG servos to 1.15V and V
SW
FB
–
+
+
Bat-Track HV CONTROL
V
3.6V
BAT + 0.3V
OUT
OmV
IDEAL
DIODE
15mV
27
–
+
4.3V
WALL
LTC3576/LTC3576-1
+
–
–
+
BATTERY POWER
HV INPUT
IDGATE
ACPR
V
BUS
BAT
OUT
SW
36
33
31
32
28
voltage has approximately
3576 F03
+
SINGLE CELL
Li-Ion
OPTIONAL EXTERNAL
IDEAL DIODE PMOS
3.5V TO
(BAT + 0.3V)
TO SYSTEM LOAD
BUS
BUS
BUS
BUS
21
/2Ω to
until it
once
falls
3576f