ltc3586 Linear Technology Corporation, ltc3586 Datasheet - Page 16

• Manufacturer Part Number: ltc3586
• Description: High Ef? Ciency Usb Power Manager With Boost, Buck-boost And Dual Bucks
• Manufacturer: Linear Technology Corporation

LTC3586
Suspend LDO
If the LTC3586 is configured for USB suspend mode,
the switching regulator is disabled and the suspend
LDO provides power to the V
power available to V
tery from running down when the portable product has
access to a suspended USB port. Regulating at 4.6V, this
LDO only becomes active when the switching converter
is disabled (Suspended). To remain compliant with the
USB specification, the input to the LDO is current limited
so that it will not exceed the 500μA low power suspend
specification. If the load on V
current limit, the additional current will come from the
battery via the ideal diode.
3.3V Always-On Supply
The LTC3586 includes a low quiescent current low dropout
regulator that is always powered. This LDO can be used to
provide power to a system pushbutton controller, standby
microcontroller or real time clock. Designed to deliver up
to 20mA, the always-on LDO requires at least a 1μF low
impedance ceramic bypass capacitor for compensation.
The LDO is powered from V
dropout at loads less than 20mA as V
If the LDO3V3 output is not used, it should be disabled
by connecting it to V
OPERATION
16
OR WALL
ADAPTER
TO USB
4
I
h
SWITCH
V
35, 36
CLPROG
CLPROG
BUS
1.188V
/
BUS
OUT
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
). This LDO will prevent the bat-
.
–
+
OUT
OUT
GATE DRIVE
OUT
PWM AND
, and therefore will enter
pin (presuming there is
exceeds the suspend
OUT
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
falls near 3.3V.
Figure 3. PowerPath Block Diagram
–
+
+
3.6V
CONSTANT CURRENT
CONSTANT VOLTAGE
BATTERY CHARGER
0.3V
+ –
V
An internal undervoltage lockout circuit monitors V
keeps the PowerPath switching regulator off until V
rises above 4.30V and is about 200mV above the battery
voltage. Hysteresis on the UVLO turns off the regulator if
V
this happens, system power at V
the battery via the ideal diode.
Battery Charger
The LTC3586 includes a constant-current / constant-volt-
age battery charger with automatic recharge, automatic
termination by safety timer, low voltage trickle charging,
bad cell detection and thermistor sensor input for out-of-
temperature charge pausing.
Battery Preconditioning
When a battery charge cycle begins, the battery charger
first determines if the battery is deeply discharged. If the
battery voltage is below V
trickle charge feature sets the battery charge current to
10% of the programmed value. If the low voltage persists
for more than 1/2 hour, the battery charger automatically
terminates and indicates via the CHRG pin that the battery
was unresponsive.
BUS
BUS
drops below 4.00V or to within 50mV of BAT. When
Undervoltage Lockout (UVLO)
IDEAL
DIODE
15mV
–
+
+
–
GATE
V
TRKL
BAT
OUT
SW
37
34
31
32
, typically 2.85V, an automatic
3586 F03
OUT
will be drawn from
+
SINGLE CELL
Li-Ion
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
3.5V TO
(BAT + 0.3V)
TO SYSTEM
LOAD
BUS
and
BUS
3586f