ISL6298-2CR4Z データシートの表示（PDF） - Renesas Electronics
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ISL6298-2CR4Z Datasheet PDF : 17 Pages
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ISL6298
Theory of Operation
The ISL6298 is an integrated charger optimized for low-
capacity single-cell Li-ion or Li-polymer batteries. It charges a
battery with the constant current (CC) and constant voltage
(CV) profile. The charge current is trimmed to have better than
10% accuracy at 250mA and is programmable up to 450mA.
The charge voltage has 1% accuracy.
Figure 20 shows the typical operating waveforms after power
on. The power is applied at t0. When the input voltage reaches
the power-on reset (POR) threshold at t1, the V2P8 pin starts
to output a 2.8V supply. This supply also powers the internal
control circuit. The POR initiates a charge cycle. Six different
ways can initiate a charge cycle, as listed in Table 1.
TABLE 1. EVENTS THAT LEADS TO A NEW CHARGE CYCLE
#
EVENT
1 Power on Reset
2 The VIN pin voltage drops below the VBAT pin voltage and
then rises back above the VBAT pin voltage
3 A new battery being inserted (detected by TEMP pin)
4 The battery voltage drops below a recharge threshold after
completing a charge cycle
5 recovery from a battery over-temperature fault
6 the EN pin is toggled from GND to floating
A charge cycle goes through a trickle mode (t1 to t2), a
constant current (CC) mode (t2 to t3) and a constant voltage
(CV) mode (t3 to t5). The total fast charge (CC and CV) time (t2
to t5) is programmed by users to prevent charging a faulty
battery for an excessively long time. At the end of the fast
charge time (t5), the charger is terminated. The charger must
reach an end-of-charge (EOC) condition before the
termination; otherwise, the charger issues a fault indication
through the FAULT pin. The charger issues a logic low signal at
the STATUS pin at the beginning of a charge cycle. When the
VIN
V2P8
POR Threshold
Charge Cycle
Charge Cycle
STATUS
FAULT
15 Cycles to
1/8 TIMEOUT
VBAT
VRECHRG
2.8V VMIN
15 Cycles
ICHARGE
IMIN
t0
t1 t2
t3
t4 t5
t6 t7
t8
FIGURE 20. TYPICAL OPERATING WAVEFORMS
FN9173 Rev 4.00
March 9, 2006
EOC condition is reached, the STATUS rises to high, as shown
at t4.
After termination, if the battery voltage drops below a recharge
threshold (t6 in Figure 20), a re-charge cycle will take place.
The total time for the recharge cycle is the total fast charge
time (t7 to t8). The trickle charge time is negligible in a
recharge cycle. More detailed description for the operation is
given below.
Power on Reset (POR)
The ISL6298 resets itself as the input voltage rises above the
POR rising threshold. The V2P8 pin outputs a 2.8V voltage,
the internal oscillator starts to oscillate, the internal timer is
reset, and the charger begins to charge the battery. The two
indication pins, STATUS and FAULT, indicate a LOW and a
HIGH logic signal respectively. Figure 20 illustrates the startup
of the charger between t0 to t2.
The ISL6298 has a typical rising POR threshold of 3.4V and a
falling POR threshold of 2.4V. The 2.4V falling threshold
guarantees charger operation with a current-limited adapter to
minimize the thermal dissipation. See more details on using a
current-limited adapter in the ISL6292 datasheet, available at
http://www.intersil.com.
Internal Oscillator
The internal oscillator (see the Block Diagram) establishes a
timing reference. The oscillation period is programmable with
an external timing capacitor, CTIME, as shown in Typical
Applications. The oscillator charges the timing capacitor to
1.5V and then discharges it to 0.5V in one period, both with
10A current. The period TOSC is:
TOSC = 0.2 106 CTIME
sec onds
(EQ. 1)
A 1nF capacitor results in a 0.2ms oscillation period.
Total Fast Charge Time
The total fast charge time TIMEOUT is also programmed by
the CTIME. A 22-stage binary counter increments each
oscillation period to set the TIMEOUT, thus,
TIMEOUT = 222 TOSC= 14 -C---1-T---n-I--M-F---E--
minutes
(EQ. 2)
A 1nF capacitor leads to 14 minutes of TIMEOUT. If a user
needs to set the TIMEOUT to 3.5 hours, a 15nF capacitor is
required. The charger must reach EOC before the charger
terminates, otherwise, a TIMEOUT fault will be issued.
Trickle Charge Time
The trickle charge time is limited to 1/8 of TIMEOUT. If the
trickle charge time (t1 to t2) exceeds the limit, a TIMEOUT fault
will be issued. The end of trickle charger is determined by the
battery voltage staying above the trickle charge threshold
(given in the Electrical Specification) for 15 consecutive cycles
of TOSC; therefore, the minimum time the charger stays in the
trickle mode is 15 cycles. Usually for a recharge cycle, the
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