LTC3566/LTC3566-2
9
3566fb
I
LOAD
(mA)
1
3.267
V
OUT1
(V)
3.300
3.311
3.333
3.322
10 100 1A
3566 G28
3.289
3.278
V
IN1
= 3V
V
IN1
= 3.6V
V
IN1
= 4.5V
V
OUT1
= 3.3V
T
A
= 27°C
TYPE 3 COMPENSATION
V
IN1
(V)
2.7
0
REDUCTION BELOW 1A (mA)
50
100
150
200
250
300
3.1 3.5 3.9 4.3
3566 G29
4.7
STEADY STATE I
LOAD
START-UP WITH A
RESISTIVE LOAD
START-UP WITH A
CURRENT SOURCE LOAD
V
OUT1
= 3.3V
T
A
= 27°C
TYPE 3 COMPENSATION
TYPICAL PERFORMANCE CHARACTERISTICS
Buck-Boost Regulator Load
Regulation
Reduction in Current
Deliverability at Low V
IN1
LDO3V3 (Pin 1): 3.3V LDO Output Pin. This pin provides
a regulated, always-on, 3.3V supply voltage. LDO3V3
gets its power from V
OUT
. It may be used for light loads
such as a watchdog microprocessor or real time clock.
A 1μF capacitor is required from LDO3V3 to ground. If
the LDO3V3 output is not used it should be disabled by
connecting it to V
OUT
.
CLPROG (Pin 2): USB Current Limit Program and Moni-
tor Pin. A resistor from CLPROG to ground determines
the upper limit of the current drawn from the V
BUS
pin.
A fraction of the V
BUS
current is sent to the CLPROG pin
when the synchronous switch of the PowerPath switching
regulator is on. The switching regulator delivers power
until the CLPROG pin reaches 1.188V. Several V
BUS
cur-
rent limit settings are available via user input which will
typically correspond to the 500mA and the 100mA USB
specifi cations. A multilayer ceramic averaging capacitor
or R-C network is required at CLPROG for fi ltering.
NTC (Pin 3): Input to the Thermistor Monitoring Circuits.
The NTC pin connects to a battery’s thermistor to deter-
mine if the battery is too hot or too cold to charge. If the
battery’s temperature is out of range, charging is paused
until it re-enters the valid range. A low drift bias resistor
is required from V
BUS
to NTC and a thermistor is required
from NTC to ground. If the NTC function is not desired,
the NTC pin should be grounded.
FB1 (Pin 4): Feedback Input for the (Buck-Boost) Switching
Regulator. When the regulator’s control loop is complete,
this pin servos to a fi xed voltage of 0.8V.
V
C1
(Pin 5): Output of the Error Amplifi er and Voltage Com-
pensation Node for the (Buck-Boost) Switching Regulator.
External Type I or Type III compensation (to FB1) connects
to this pin. See Applications Information section for select-
ing buck-boost loop compensation components.
GND (Pins 6, 12): Power GND pins for the buck-boost.
SWAB1 (Pin 7): Switch Node for the (Buck-Boost) Switch-
ing Regulator. Connected to internal power switches A
and B. External inductor connects between this node and
SWCD1.
MODE (Pin 8): Logic Input. Mode enables Burst Mode
functionality for the buck-boost switching regulator when
pin is set high. Has a 1.6μA internal pull-down current
source.
V
IN1
(Pin 9): Power Input for the (Buck-Boost) Switching
Regulator. This pin will generally be connected to V
OUT
(Pin 20). A 1μF(min) MLCC capacitor is recommended
on this pin.
V
OUT1
(Pin 10): Regulated Output Voltage for the (Buck-
Boost) Switching Regulator.
Buck-Boost Regulator Load Step,
0mA to 300mA
CH1 V
OUT1
AC 100mV/DIV
CH2 I
LOAD
DC 200mA/DIV
100μs/DIVV
IN1
= 4.2V
V
OUT1
= 3.3V
L = 2.2μH
C
OUT
= 47μF
3566 G30
PIN FUNCTIONS
T
A
= 25°C unless otherwise noted.
