ltc4001 Linear Technology Corporation, ltc4001 Datasheet - Page 5

• Manufacturer Part Number: ltc4001
• Description: 2a Synchronous Buck Li-ion Charger
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
VOLTAGE (V
BAT (Pin 1): Battery Charger Output Terminal. Connect a
10µF ceramic chip capacitor between BAT and PGND to
keep the ripple voltage small.
SENSE (Pin 2): Internal Sense Resistor. Connect to exter-
nal inductor.
PGND (Pin 3): Power Ground.
GNDSENS (Pin 4): Ground Sense. Connect this pin to the
negative battery terminal. GNDSENS provides a Kelvin
connection for PGND and must be connected to PGND
schematically.
SW (Pin 5): Switch Node Connection. This pin connects to
the drains of the internal main and synchronous power
MOSFET switches. Connect to external inductor.
EN (Pin 6): Enable Input Pin. Pulling the EN pin high places
the LTC4001 into a low power state where the BAT drain
current drops to less than 3µA and the supply current is
reduced to less than 50µA. For normal operation, pull the
pin low.
CHRG (Pin 7): Open-Drain Charge Status Output. When
the battery is being charged, CHRG is pulled low by an
TYPICAL PERFOR A CE CHARACTERISTICS
CURRENT (I
CURRENT (I
EN PIN (V
SOFT-START
INDUCTOR
U
0.5A/DIV
0.5A/DIV
1V/DIV
5V/DIV
INPUT
SS
EN
IN
L
)
)
)
)
U
0
0
0
0
Soft-Start (PWM Mode)
V
V
BAT
IN
= 5V
= 3.5V
U
2ms/DIV
W
U
4001 G09
300
250
150
400
350
200
100
50
0
300
IDET Threshold vs R
R
PROG
400
500
= 549Ω
600
internal N-channel MOSFET. When the charge current
drops below the IDET threshold (set by the R
ming resistor) for more than 5milliseconds, the N-channel
MOSFET turns off and a 30µA current source is connected
from CHRG to ground. (This signal is latched and is reset
by initiating a new charge cycle.) When the timer runs out
or the input supply is removed, the current source will be
disconnected and the CHRG pin is forced to a high imped-
ance state. A temperature fault causes this pin to blink.
PV
connects to the power devices inside the chip. V
from 4V to 5.5V for normal operation. Operation down to
the undervoltage lockout threshold is allowed with current
limited wall adapters. Decouple with a 10µF or larger
surface mounted ceramic capacitor.
V
connects to the inputs of all input comparators (UVL, V
to V
this chip. When the BATSENS pin rises to within 30mV of
V
50µA. Tie this pin directly to the terminal of the PV
decoupling capacitor.
R
700
INSENSE
INSENSE
IDET
IN
BAT
800
(Ω)
(Pin 8): Positive Supply Voltage Input. This pin
IDET
). It also supplies power to the controller portion of
900
, the LTC4001 enters sleep mode, dropping I
(Pin 9): Positive Supply Sense Input. This pin
for
1000
1100
4001 G10
1200
1V/DIV
CHRG
CHRG Pin Temperature Fault
Behavior (Detail)
TIME (20µs/DIV)
LTC4001
IDET
program-
IN
ranges
IN
5
4001 G11
4001f
to
IN
IN