LTC3586-2 LINER [Linear Technology], LTC3586-2 Datasheet - Page 17

• Manufacturer Part Number: LTC3586-2
• Description: High Efficiency USB Power Manager
• Manufacturer: LINER [Linear Technology]

Suspend LDO
If the LTC3586-2/LTC3586-3 are configured for USB sus-
pend mode, the switching regulator is disabled and the
suspend LDO provides power to the V
there is power available to V
battery 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 LTC3586-2/LTC3586-3 include 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. De-
signed 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
therefore will enter dropout at loads less than 20mA as
V
should be disabled by connecting it to V
OPERATION
OR WALL
ADAPTER
OUT
TO USB
falls near 3.3V. If the LDO3V3 output is not used, it
4
I
h
SWITCH
V
35, 36
CLPROG
CLPROG
BUS
1.188V
/
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
–
+
BUS
GATE DRIVE
). This LDO will prevent the
OUT
PWM AND
exceeds the suspend
OUT
AVERAGE OUTPUT
VOLTAGE LIMIT
OUT
CONTROLLER
pin (presuming
Figure 3. PowerPath Block Diagram
.
–
+
+
OUT
3.6V
, and
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 LTC3586-2/LTC3586-3 include a constant-current/
constant-voltage 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
LTC3586-2/LTC3586-3
–
+
+
–
V
GATE
TRKL
BAT
OUT
SW
37
34
31
32
, typically 2.85V, an automatic
358623 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
17
358623f
and
BUS