LTC1731-4.2 Linear Technology, LTC1731-4.2 Datasheet - Page 3

• Manufacturer Part Number: LTC1731-4.2
• Description: Lithium-Ion Linear Battery Charger Controller
• Manufacturer: Linear Technology

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
PIN
temperature range, otherwise specifications are at T
BAT (Pin 1): Battery Sense Input. A bypass capacitor of at
least 10 F is required to keep the loop stable when the
battery is not connected. A precision internal resistor
divider sets the final float potential on this pin. The resistor
divider is disconnected in sleep mode.
CHRG (Pin 2): Open-Drain Charge Status Output. When
the battery is being charged, the CHRG pin is pulled low by
an internal N-channel MOSFET. When the charge current
drops to 10% of the full-scale current for at least 0.32
seconds, the N-channel MOSFET turns off and a 100 A
current source is connected from the CHRG pin to GND.
When the timer runs out or the input supply is removed,
the current source will be disconnected and the CHRG pin
is forced into a high impedance state.
TIMER (Pin 3): Timer Capacitor and Constant-Voltage
Mode Disable Input Pin. The timer period is set by placing
a capacitor, C
(C
connected to V
and the chip will operate in constant-current mode only.
Short the TIMER pin to GND to disable the internal timer
function.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
V
I
V
I
V
I
t
V
PROG
CHRG
C/10
TIMER
ASD
DIS
PROG
CHRG
CLAMP
TIMER
U
FUNCTIONS
PARAMETER
Automatic Shutdown Threshold Voltage
Voltage Mode Disable Threshold Voltage
PROG Pin Current
PROG Pin Load Regulation
PROG Pin Voltage
CHRG Pin Weak Pull-Down Current
CHRG Pin Output Low Voltage
End of Charge Indication Current Level
TIMER Accuracy
DRV Pin Clamp Voltage
• 3 hours)/(0.1 F). When the TIMER pin is
U
TIMER
CC
, the constant-voltage mode is disabled
, to GND. The timer period is t
U
CONDITIONS
(V
(V
V
Internal Pull-Up Current, No R
PROG Pin Source Current, V
R
V
I
R
C
V
CHRG
TIMER
CHRG
TIMER
CLAMP
PROG
PROG
CC
CC
A
– V
– V
= 25 C. V
= 5mA
= 1V
=19.6k
= 19.6k, R
= 0.1 F
= V
BAT
BAT
TIMER
The
CC
) High to Low
) Low to High
– V
=
CC
SENSE
DRV
denotes the specifications which apply over the full operating
= 6V unless otherwise noted.
, I
DRIVE
= 0.2
Note 2: The LTC1731-4.2 is guaranteed to meet performance
specifications from 0 C to 70 C. Specifications over the – 40 C to 85 C
operating temperature range are assured by design, characterization and
correlation with statistical process controls. Guaranteed I grade parts are
available, consult factory.
GND (Pin 4): Ground.
PROG (Pin 5): Charge Current Program and Shutdown
Input Pin. The charge current is programmed by connect-
ing a resistor, R
= (V
into shutdown by floating the PROG pin and allowing the
internal 2.5 A current source to pull the pin above the
2.457V shutdown threshold voltage.
DRV (Pin 6): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. The impedance is high at this pin,
therefore, a high gain PNP pass transistor should be used.
The DRV pin is internally clamped to 8V (max) below V
V
within 54mV of V
mode, dropping I
Bypass this pin with a 1 F capacitor.
SENSE (Pin 8): Current Sense Input. A sense resistor,
R
This resistor is chosen using the following equation:
CC
SENSE
R
= 50 A
PROG
(Pin 7): Positive Input Supply Voltage. When V
SENSE
PROG
PROG
, must be connected from V
• 800 )/(R
5mV
= (V
PROG
PROG
CC
CC
, the LTC1731-4.2 is forced into sleep
to 7 A. V
• 800 )/(R
PROG
to ground. The charge current is I
• R
SENSE
CC
MIN
300
5.6
30
40
25
PROG
70
ranges from 4.5V to 12V.
LTC1731-4.2
). The IC can be forced
CC
2.457
• I
TYP
100
2.5
0.6
6.5
54
69
50
10
to the SENSE pin.
BAT
)
MAX
100
130
100
1.2
90
BAT
UNITS
3
BAT
CC
mV
mV
mA
is
%
V
V
A
A
A
V
V
.