LTC1734
5
1734fa
For more information www.linear.com/LTC1734
Typical perForMance characTerisTics
Program Pin Voltage
vs Charge Current (700mA)
Program Pin Voltage for I
BAT1
/10
vs Temperature and Supply Voltage
Program Pin Voltage for I
BAT2
/10
vs Temperature and Supply Voltage
I
BAT2
(mA)
0
V
PROG
(V)
1.4
300
1734 G10
0.8
0.4
100 200 400
0.2
0
1.6
1.2
1.0
0.6
500 600 700
V
CC
= 5V
T
A
= 25°C
R
PROG
= 2.15k
PNP = FCX589
LIMITS AT 6mV DUE TO
PROGRAMMING PIN PULL-UP
CURRENT (I
PROGPU
)
TEMPERATURE (°C)
–50
140
V
PROG
(mV)
150
160
0
50
75
1734 G11
–25
25
100
125
R
PROG
= 7.5k
PNP = FCX589
V
CC
= 8V
V
CC
= 4.55V
TEMPERATURE (°C)
–50
140
V
PROG
(mV)
150
160
0
50
75
1734 G12
–25
25
100
125
R
PROG
= 2.15k
PNP = FCX589
V
CC
= 8V
V
CC
= 4.55V
I
SENSE
(Pin 1): Sense Node for Charge Current. Current
from V
CC
passes through the internal current sense resistor
and reappears at I
SENSE
to supply current to the external
PNP emitter. The PNP collector provides charge current
to the battery.
GND (Pin 2): Ground. Provides a reference for the internal
voltage regulator and a return for all internal circuits. When
in the constant voltage mode, the LTC1734 will precisely
regulate the voltage between the BAT and GND pins. The
battery ground should connect close to the GND pin to
avoid voltage drop errors.
V
CC
(Pin 3): Positive Input Supply Voltage. This pin sup-
plies power to the internal control circuitry and external
PNP transistor through the internal current sense resistor.
This pin should be bypassed to ground with a capacitor
in the range of 1µF to 10µF.
PROG
(Pin 4): Charge Current Programming, Charge Cur
-
rent Monitor and Manual Shutdown Pin. Provides a virtual
reference voltage of
1.5
V for an external resistor (R
PROG
)
tied between this pin and ground that programs the bat-
tery charge current when the charger is in the constant
current mode
.
The typical charge current will be 1000
times greater than the current through this resistor (I
BAT
= 1500/R
PROG
). This pin also allows for the charge current
to be monitored. The voltage on this pin is proportional
to the charge current where 1.5V corresponds to the full
programmed current. Floating this pin allows an internal
current source to pull the pin voltage above the shutdown
threshold voltage. Because this pin is in a signal path,
excessive capacitive loading can cause AC instability.
See the Applications Information section for more details.
BAT (Pin 5): Battery Voltage Sense Input. A precision
internal resistor divider sets the final float voltage on this
pin. This divider is disconnected in the manual shutdown
or sleep mode. When charging, approximately 34µA
flows into the BAT pin. To minimize float voltage errors,
avoid excessive resistance between the battery and the
BAT pin. For dynamically stable operation, this pin usu
-
ally requires a minimum bypass capacitance to ground
of 5µF to frequency compensate for the high frequency
inductive effects of the batter
y and wiring.
DRIVE (Pin 6): Base Drive Output for the External PNP
Pass Transistor. Provides a controlled sink current that
drives the base of the PNP. This pin has current limiting
protection for the LTC1734.
pin FuncTions
