UG-467
Evaluation Board User Guide
Rev. 0 | Page 8 of 12
FAST CHARGE CURRENT
To measure the fast change current, do the following:
1.
Set the V
IN
supply voltage to 5.0 V.
2.
Set V
ISO_B
to 3.9 V.
3.
Verify that the GUI
Battery Status
indicator shows
BAT_SNS > Vweak
.
4.
Set the VINx input current limit to the maximum value
2100 mA.
5.
Measure the charge current into the battery. The default
value for the fast charge current is 750 mA. It is possible to
change the fast charge current setting from 50 mA to 1300 mA
using the GUI.
6.
The fast charge current may be reduced because of the
following conditions:
•
The V
BAT_SNS
level is close to the termination voltage V
TRM
(default 4.20 V).
•
The die temperature T
J
exceeds the isothermal charging
temperature T
LIM
(typically 115 °C).
TERMINATION VOLTAGE AND END OF CHARGE
(EOC) CURRENT
Measuring Termination Voltage Using SMU or Battery
Simulator
The
fast charge constant voltage (CV) regulation is
optimized for batteries with series resistance in the 100 mΩ to
250 mΩ range. When using a SMU or a battery simulator
connected to the ISO_Bx, set the series resistance (R
S
within this range.
Some battery simulators, such as the Keithley 2306, have
programmable source resistance integrated in the instrument
itself. For SMU units, use an external resistor to obtain accurate
measurement results of the termination voltage.
To measure the termination voltage, do the following:
1.
Set the V
VIN
supply voltage to 5.0 V.
2.
Set the termination voltage to 4.2 V using the GUI.
3.
Disable the EOC by setting the EN_EOC bit (D2) to low in
the functional settings register, Register 0x07.
4.
Disable charge complete timer register, Register 0x06, using
the GUI (see Figure 3).
5.
Sweep V
ISO_B
up until
Charger Status
indicator in the GUI
shows
Fast Charge (CV-Mode)
.
6.
Sweep V
ISO_B
up until charge current has dropped to 50 mA. In
fast charge CV mode, 1 mV step up of V
ISO_B
can reduce the
charge current by several mA.
7.
Measure termination voltage between the BAT_SNS (TP20)
and GND_S (TP9) nodes.
Measuring EOC Current
To measure the EOC current, do the following:
8.
Use the GUI to set the termination current to 52.5 mA.
9.
Step V
ISO_B
down 100 mV.
10.
Enable the EOC by setting the EN_EOC bit (D2) to high in
the functional settings register, Register 0x07.
11.
Step V
ISO_B
up and monitor the charge current for each step
until the
Charger Status
indicator in the GUI shows
Charge Complete
. The last charge current value before
Charge Complete
is the charge complete current threshold.
Charging stops and there is no current flowing into the
ISO_Bx node.
Measuring Recharge Voltage
To measure the recharge voltage, do the following:
12.
Step V
ISO_B
down, and monitor the voltage until the
Charger Status
indicator on the GUI shows
Fast Charge
(CC-Mode)
and charge current flows to the ISO_Bx node.
Last value before the charger status change is the recharge
voltage level. With default settings, the recharge voltage
threshold is 3.94 V (V
ISO_B
).
13.
Use the GUI to change the termination current and recharge
voltage programming. Repeat Step 9 to Step 12 to evaluate
different settings.
