LTC3552-1 Linear Technology, LTC3552-1 Datasheet - Page 8

• Manufacturer Part Number: LTC3552-1
• Description: Standalone Linear Li-Ion Battery Charger and Dual Synchronous Buck Converter
• Manufacturer: Linear Technology

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PI FU CTIO S
LTC3552-1
ITERM (Pin 1): Charge Termination Program. The charge
termination current threshold is programmed by connect-
ing a 1% resistor, R
ITERM, is set by the following formula:
BAT (Pin 2): Charge Current Output. Provides charge cur-
rent to the battery from the internal P-channel MOSFET,
and regulates the fi nal fl oat voltage to 4.2V. An internal
precision resistor divider from this pin sets the fl oat volt-
age. This divider is disconnected in shutdown mode to
minimize current drain from the battery.
⎯ C ⎯ H ⎯ R ⎯ G (Pin 3): Charge Status Open-Drain Output. When
the battery is charging, the ⎯ C ⎯ H ⎯ R ⎯ G pin is pulled low by an
internal N-channel MOSFET. When the charge cycle is
completed, ⎯ C ⎯ H ⎯ R ⎯ G becomes high impedance.
RUN2 (Pin 4): Regulator 2 Enable. Forcing this pin to
V
regulator 2 to shut down. This pin must be driven; do
not fl oat.
SW2 (Pin 5): Regulator 2 Switch Node Connection to the
Inductor. This pin swings from V
RUN1 (Pin 6): Regulator 1 Enable. Forcing this pin to V
enables regulator 1, while forcing it to GND causes regulator
1 to shut down. This pin must be driven; do not fl oat.
V
tor 2. Internal resistors divide the output voltage down
for comparison to the internal reference voltage.
V
the feedback voltage from internal resistive divider across
the output. Normal voltage for this pin is 0.6V.
V
the feedback voltage from internal resistive divider across
the output. Normal voltage for this pin is 0.6V.
V
tor 1. Internal resistors divide the output voltage down
for comparison to the internal reference voltage.
8
OUT1
CC
OUT2
FB2
FB1
U
I
TERM
enables regulator 2, while forcing it to GND causes
(Pin 8): Output Feedback for Regulator 2. Receives
(Pin 9): Output Feedback for Regulator 1. Receives
(Pin 10): Output Voltage Feedback Pin for Regula-
(Pin 7): Output Voltage Feedback Pin for Regula-
=
U
R
100
TERM
V
TERM
,
U
R
TERM
, to ground. The current threshold
=
I
100
TERM
CC
V
to GND.
CC
V
power to the switchers. Must be closely decoupled
to GND.
SW1 (Pin 12): Regulator 1 Switch Node Connection to the
Inductor. This pin swings from V
PROG (Pin 13): Charge Current Program and Charge
Current Monitor. Charge current is programmed by con-
necting a 1% resistor, R
in constant-current mode, this pin servos to 1V. In all
modes, the voltage on this pin can be used to measure
the charge current using the following formula:
This pin is clamped to approximately 2.4V. Driving this pin to
voltages beyond the clamp voltage should be avoided.
V
the charger. V
should be bypassed with at least a 1µF capacitor. When
V
enters shutdown mode dropping the battery drain current
to less than 2µA.
⎯ P ⎯ W ⎯ R (Pin 15): Power Supply Status Open-Drain Out-
put. When V
out threshold and at least 100mV above V
⎯ P ⎯ W ⎯ R pin is pulled to ground; otherwise, the pin is high
impedance.
⎯ E ⎯ N (Pin 16): Enable Input. A logic high on the ⎯ E ⎯ N pin will
put the charger into shutdown mode where the battery
drain current is reduced to less than 2µA and the supply
current is reduced to less than 50µA. A logic low or fl oating
the ⎯ E ⎯ N pin (allowing an internal 2MΩ pull-down resistor
to pull this pin low) enables charging.
Exposed Pad (GND) (Pin 17): Ground. The exposed
backside of the package (Pin 17) is ground and must be
soldered to the PCB for maximum heat transfer.
CC
IN
IN
I
BAT
is within 100mV of the BAT pin voltage, the charger
(Pin 14): Charger Input Supply. Provides power to
(Pin 11): Buck Regulators Input Supply. Provides
=
R
V
PROG
PROG
IN
IN
is greater than the undervoltage lock-
can range from 4.25V to 8V. This pin
• 1000
PROG
, to ground. When charging
CC
to GND.
BAT
, the
35521f