LTC1734ES6-4.1#TRMPBF Linear Technology, LTC1734ES6-4.1#TRMPBF Datasheet - Page 8

• Manufacturer Part Number: LTC1734ES6-4.1#TRMPBF
• Description: IC BATT CHRGR LI-ION LIN SOT23-6
• Manufacturer: Linear Technology

Specifications of LTC1734ES6-4.1#TRMPBF

• Function: Charge Management
• Battery Type: Li-Ion, NiCd, NiMH
• Voltage - Supply: 4.55 V ~ 8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-6 Thin, TSOT-23-6
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LTC1734ES6-4.1#PBF; LTC1734ES6-4.1#PBF

APPLICATIONS
LTC1734
Programming Constant Current
When in the constant current mode, the full-scale charge
current (C) is programmed using a single external resistor
between the PROG pin and ground. This charge current
will be 1000 times greater than the current through the
program resistor. The program resistor value is selected
by dividing the voltage forced across the resistor (1.5V)
by the desired resistor current.
The LTC1734 is designed for a maximum current of
approximately 700mA. This translates to a maximum
PROG pin current of 700 A and a minimum program
resistor of approximately 2.1k. Because the PROG pin is in
a closed-loop signal path, the pole frequency must be kept
high enough to maintain adequate AC stability by avoiding
excessive capacitance on the pin. See the Stability section
for more details.
The minimum full-scale current that can be reliably pro-
grammed is approximately 50mA, which requires a pro-
gram resistor of 30k. Limiting capacitive loading on the
program pin becomes more important when high value
program resistors are used. In addition, the current
8
(FILTERED)
CURRENT
MONITOR
CHARGE
OPTIONAL FILTER
Figure 3. Programmable Current Source with Output Current of 0mA, 200mA, 500mA or 700mA
0.1 F TO
0.5 F
1k
U
Figure 2. Logic Control Programming of Output Current to 0mA, 200mA, 500mA or 700mA
CONTROL 1
PIN 4
INFORMATION
U
Q1
2N7002
V
5V
3k
IN
(UNFILTERED)
CONTROL 2
1 F
CURRENT
MONITOR
CHARGE
W
CONTROL 1
Q2
2N7002
7.5k
3
2
4
V
GND
PROG
CC
Q1
2N7002
V
LTC1734
5V
3k
IN
U
CONTROL 2
I
DRIVE
1 F
SENSE
BAT
*OBSERVE MAXIMUM TEMPERATURE
1
6
5
Q2
2N7002
7.5k
3
2
4
V
GND
PROG
CC
LTC1734
monitoring accuracy can degrade considerably at very
low current levels. If current monitoring is desired, a
minimum full-scale current of 200mA is recommended.
Different charge currents can be programmed by various
means such as by switching in different program resistors
as shown in Figures 2 and 3. A voltage DAC connected
through a resistor to the PROG pin or a current DAC
connected in parallel with a resistor to the PROG pin can
also be used to program current (the resistor is required
with the I
Stability section). Another means is to use a PWM output
from a microcontroller to duty cycle the charger into and
out of shutdown to create an average current (see Manual
Shutdown section for interfacing examples). Because
chargers are generally slow to respond, it can take up to
approximately 300 s for the charger to fully settle after a
shutdown is deasserted. This delay must be accounted for
unless the minimum PWM low duration is about 3ms or
more. Shutdown occurs within a few microseconds of a
shutdown command. The use of PWM can extend the
average current to less than the normal 200mA minimum
constant current.
LOAD
FZT549*
I
DRIVE
SENSE
1734 F03
BAT
I
LOAD
1
6
5
DAC
CURRENT
to maintain AC stability as discussed in the
200mA
500mA
700mA
FZT549
0
10 F
I
BAT
CONTROL 1
HIGH
HIGH
LOW
LOW
1734 F02
SINGLE
Li-Ion
BATTERY
CHARGE CURRENT
200mA
500mA
700mA
CONTROL 2
0
HIGH
HIGH
LOW
LOW
CONTROL 1
HIGH
HIGH
LOW
LOW
CONTROL 2
LOW
HIGH
LOW
HIGH