DESCRIPTION
dc2133a F01
DEMO MANUAL DC2133A
LTC4079
60V, 250mA Linear Charger
with Low Quiescent Current
Demonstration circuit 2133A features a simple battery
®
charger circuit using the LTC
4079 high-voltage mono-
lithic linear charger. The DC2133 has an input voltage
from 2.7V to 60V and is capable of supplying up
range
to 250mA charge current. The charge voltage is jumperselectable to 4.2V or 8.4V. Charge current is adjustable
via the PROG pin and initially programmed for 99mA. In
shutdown or when unpowered, LTC4079 consumes only
10nA from the battery.
DC2133A is initially configured to enable charging from
application of V
PERFORMANCE SUMMARY
PARAMETER CONDITIONS TYPICAL VALUE
Input Voltage Range 2.7V to 60V
Default Charging Voltage V
Default Charging Current R
PROG Pin Voltage R
Input Regulation Voltage EN = REG (JP1) 10.3V
Default Charge Timer C
above the LTC4079 UVLO threshold.
IN
Specifications are at TA = 25°C
= 4.2 4.2V
BAT
= 3.01k 99mA
PROG
= 3.01k, I
PROG
= 0.068μF 3h 45 min
TMR
The NTC input is connected to an on-board resistance to
enable charging with only a 2-wire battery connection;
however an external thermistor may be used with the
NTC test point.
Termination is accomplished by timer method. Charging
status is reflected by the CHRG LED.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2133A
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
= 99mA 2.5V
CHG
100
90
80
70
60
(mA)
50
BAT
I
40
30
20
10
0
240mAh Li-Ion
= 5V
V
IN
= 3.01k
R
PROG
= 0.068µF
C
TMR
V
BAT
0
1
I
BAT
TIME (HOURS)
CHRG
C/10
TERMINATION
Figure 1. Typical Battery Charge Cycle
5.2
5.0
4.8
V
4.6
BAT
& V
4.4
CHRG
4.2
(V)
4
3.8
3.6
3.4
3.2
532 4
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DEMO MANUAL DC2133A
I
250 • V
PROG
QUICK START PROCEDURE
Demonstration circuit 2133 is easy to set up to evaluate
the performance of LTC4079. Refer to Figure 2 for proper
measurement equipment setup and follow the procedure
below.
1. The jumpers are initially set as below for a typical 4.2V
charging application:
JP1 JP2 JP3 JP4 JP5
EN NTC TIMER VBAT LED
ON INT ON 4.2 ON
2. With all power off, connect the input supply, battery,
and meters as shown in Figure 2.
Note: Depending on the input cable and power supply
impedance, hot plugging an input supply may cause
overvoltage transients that can damage the board. R1
and C1 form an input transient damping network that
mitigates this. See AN-88 for component selection.
3. Turn on the input power supply. Adjust the input voltage
and current limit to the desired value.
4. Monitor the PROG pin voltage for a scaled representa
-
tion of the output current according to the relationship:
5. Allow the battery to charge for a complete cycle. CHRG
will disable the LED when the charge current has dropped
below 10mA, but the timer will continue to run and
charge current will flow until the timer period ends.
Optional
1. While powered off, change the setting of the EN jumper,
JP1, to REG to evaluate the enable input regulation
feature, or to OFF to disable charging.
2. Use an external thermistor connected to the NTC jumper,
JP2, set to EXT.
3. To terminate charge on current, disable the TIMER
input with JP3 set to OFF. LTC4079 will terminate on
C/10only.
4. The CHRG LED can be disconnected to measure the
true quiescent current of the LTC4079 in shutdown or
for connection to external pull-up logic by setting the
LED jumper, JP5 to OFF.
5. To change the battery charging voltage, set the V
BAT
jumper, JP4. Alternatively, the feedback resistors may
be adjusted for custom values, according to the battery
voltage.
PROG
R
BAT
=
Note: Minimize capacitance on the PROG pin to prevent
charger instability.
Note: DO NOT change the V
with VIN applied.
BAT
dc2133afa
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