LTC3586-1_15 Datasheet, PDF (16/36 Pages) Linear Technology – High Efficiency USB Power Manager with Boost, Buck-Boost and Dual Bucks

LTC3586/LTC3586-1
OPERATION
Suspend LDO
If the LTC3586/LTC3586-1 are configured for USB suspend
mode, the switching regulator is disabled and the suspend
LDO provides power to the V_OUT pin (presuming there is
power available to V_BUS). This LDO will prevent the bat-
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_OUT exceeds the suspend
current limit, the additional current will come from the
battery via the ideal diode.
3.3V Always-On Supply
The LTC3586/LTC3586-1 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_OUT, and
therefore will enter dropout at loads less than 20mA as
V_OUT falls near 3.3V. If the LDO3V3 output is not used, it
should be disabled by connecting it to V_OUT.
V_BUS Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors V_BUS and
keeps the PowerPath switching regulator off until V_BUS
rises above 4.30V and is about 200mV above the battery
voltage. Hysteresis on the UVLO turns off the regulator if
V_BUS drops below 4.00V or to within 50mV of BAT. When
this happens, system power at V_OUT will be drawn from
the battery via the ideal diode.
Battery Charger
The LTC3586/LTC3586-1 include a constant-current/con-
stant-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_TRKL, typically 2.85V, an automatic
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.
TO USB
OR WALL
ADAPTER
16
V_BUS
35, 36
I_SWITCH/
h_CLPROG
PWM AND
GATE DRIVE
CONSTANT-CURRENT
CONSTANT-VOLTAGE
BATTERY CHARGER
IDEAL
DIODE
+
–
15mV ^+–
CLPROG –
4
+
1.188V
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
0.3V
+–
3.6V
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
Figure 3. PowerPath Block Diagram
SW
37
V_{OUT 34}
GATE
31
BAT
32
3586 F03
3.5V TO
(BAT + 0.3V)
TO SYSTEM
LOAD
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
+ _{SINGLE CELL}
Li-Ion
3586fb