ISL6297 Intersil Corporation, ISL6297 Datasheet - Page 12

• Manufacturer Part Number: ISL6297
• Description: Li-ion/Li Polymer Battery Charger
• Manufacturer: Intersil Corporation

finishes (either when the EOC condition is qualified or when
the TIMEOUT completes) the ISL6297 releases the RED
output and pulls the GRN pin low to drive a green indicator
while the red indicator turns off. The green LED remains on
unless the input power is recycled, or a fault occurs. During
a recharge operation, the indicator remains green.
When a temperature fault happens, both the RED and the
GRN pins turn on to indicate a yellow color. This fault is
cleared automatically when the temperature again returns to
the normal region. If the FAULT is non-temperature related,
the yellow indicator flashes. This type of fault is latched and
can only be reset by toggling the EN pin or cycling the input
power. Table 2 summarizes the LED indications.
Because the LED outputs provide a constant 10mA current
sink, no external resistors are necessary.
VSEN Pin
When the charger is providing a large current to the cell,
there can be significant voltage drop in the PCB trace
between the charger output and the battery positive terminal.
To minimize this effect, the VSEN pin input provides a low
current monitoring path. This provides a more accurate
reading of the battery voltage. Figure 7 shows the internal
voltage feedback circuit.
Plug In Indication
Charging
Full Charge (EOC) or recharging
Short circuit Error or trickle charge
TIMEOUT error
Over/Under Ambient Temperature
Idle state
TABLE 2. LED INDICATION SUMMARY
STATUS
12
RED GRN
H
H
H
H
H
L
L
L
L
L
H
H
H
H
H
L
L
L
L
L
Red (500ms)
Green (500ms)
Yellow (500ms)
Off (500ms)
Red
Green
Yellow (Flashing
1Hz rate)
Yellow
Off or Battery (+)
terminal not
connected
INDICATION
ISL6297
THERMAGUARD™ Charge Current Thermal
Foldback
Over-heating is always a concern in a linear charger or in the
linear region for a dual mode charger. The charge current
thermal foldback function in the ISL6297 frees users from
the over-heating concern.
Figure 8 shows the current signals at the summing node of
the current error amplifier CA in the Block Diagram. I
reference. I
block. The I
internal temperature reaches approximately +100°C; then I
rises at a rate of 1μA/°C. When I
loop forces the sensed current I
rate. As a mirrored current, the charge current is 100,000
times that of the sensed current and reduces at a rate of
100mA/°C. For a charger with the constant charge current
set at 1A, the charge current is reduced to zero when the
internal temperature rises to +110°C. The actual charge
current settles between +100°C to +110°C.
Usually the charge current should not drop below I
because of the thermal foldback. If, in some extreme case
this does happen, the charger does not indicate end-of-
charge unless the battery voltage is already above the
recharge threshold.
FIGURE 7. THE INTERNAL VOLTAGE FEEDBACK CIRCUIT
FIGURE 8. CURRENT SIGNALS AT THE AMPLIFIER CA INPUT
T
T
is the current from the Temperature Monitoring
has no impact on the charge current until the
Enable
VA
+
-
V
REF
Q1
R3
R2
SEN
VSEN
T
BAT
100
rises, the current control
O
to reduce at the same
C
I
R
Temperature
I
SEN
I
T
March 20, 2007
MIN
R
FN9215.1
is the
T