ISL6298-2CR3Z Просмотр технического описания (PDF) - Renesas Electronics
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ISL6298-2CR3Z Datasheet PDF : 17 Pages
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ISL6298
trickle charge time is 15 cycles (t6 to t7 in Figure 20). If the
battery voltage falls below the trickle charge threshold during
the 15 cycles, the 15-cycle counter is reset (not the total-
trickle-charge-time counter) and the charger remains in the
trickle mode.
Disabling TIMEOUT Limit
The TOEN pin allows the user to disable the fast charge
TIMEOUT limit by pulling the TOEN pin to LOW or shorting it to
GND. When this happens, the charger never terminates. The
STATUS pin still issues the EOC indication when the EOC
condition is reached. The EOC indication is latched and does
not change until a new charge cycle starts, initiated by the
events listed in Table 1. Leaving the TOEN pin floating is
recommended to enable the TIMEOUT. Driving the TOEN pin
above 3.0V is not recommended. The trickle charge time limit
can never be disabled. For the 3x3 DFN package option, the
TOEN pin is left floating internally and, therefore, the
TIMEOUT cannot be disabled.
CC Mode Current Programming
The charge current is programmed by the IREF pin. There are
three ways to program the charge current:
1. driving the IREF pin above 1.3V
2. driving the IREF pin below 0.4V,
3. or using the RIREF as shown in the Typical Applications.
The voltage of IREF is regulated to a 0.8V reference voltage
when not driven by any external source. The charging current
during the CC mode is 25,000 times that of the current in the
RIREF resistor. Hence, depending on how the IREF pin is
used, the charge current is,
255 m A
ICHARGE=
-R--0--I-.-R-8---E-V---F-- 25000A
100 m A
VIREF 1.3V
RIREF
VIREF 0.4V
(EQ. 3)
The internal reference voltage at the IREF pin is capable of
sourcing less than 100A current. When pulling down the IREF
pin with a logic circuit, the logic circuit needs to be able to sink
at least 100A current.
The actual charge current may be affected by the thermal
foldback function. See the Thermal Foldback section for more
details.
Trickle Mode Current
The charge current in the trickle mode is 20% of the
programmed CC mode charge current, that is:
ITRICKLE = 0.2 ICHARGE
(EQ. 4)
where ICHARGE is the charge current given in EQ. 3.
End-of-Charge (EOC) Current
The EOC current IEOC sets the level at which the charger
starts to indicate the end of the charge with the STATUS pin, as
shown in Figure 20. The IEOC is set in two ways:
1. By connecting a resistor between the IMIN pin and ground,
2. Or by connecting the IMIN pin to the V2P8 pin.
When programming with the resistor, the IEOC is set in the
equation below:
IEOC = 2500 R-V----IR--M---E--I-F-N--= 2500 R---0--I-.-M-8---V-I--N--A
(EQ. 5)
where RIMIN is the resistor connected between the IMIN pin
and the ground, as shown in the Typical Application Circuit.
When connected to the V2P8 pin, the IEOC is set to 1/10 of
ICHARGE given in EQ. 3, except when the IREF pin is shorted
to GND. Under this exception, IEOC is 5mA. For the ISL6298 in
the 3x3 DFN package, the IMIN pin is connected internally to
the V2P8 pin.
EOC Conditions
The EOC indication is asserted when the following conditions
are satisfied simultaneously:
1. The battery voltage is above the recharge threshold, and
2. The charge current is lower than the EOC current.
The two conditions can prevent prematurely indicating EOC
due to thermal foldback or other transient events.
Recharge
After a charge cycle is completed, charging is prohibited until
the battery voltage drops to a recharge threshold, VRECHRG
(see Electrical Specifications). Then a new charge cycle starts
at point t6 and ends at point t8, as shown in Figure 20. The
safety timer is reset at t6.
2.8V Voltage Regulator
The V2P8 pin is the output of an internal 2.8V linear regulator.
The 2.8V is the voltage supply for the internal control circuit and
can also be used by external circuits, such as the NTC
thermistor circuit. The external load is not recommended to
exceed 2mA. The V2P8 pin is recommended to be decoupled
with a 1F ceramic capacitor.
NTC Thermistor Interface
The TEMP pin offers an interface to an external NTC thermistor.
This pin has two functions: to monitor the battery ambient
temperature or to monitor the insertion of the battery. The
ISL6298 assumes that the NTC thermistor is inside the battery
pack. The battery and the NTC thermistor are inserted or
removed together. Removing the NTC thermistor disables the
charger.
Figure 21 shows the implementation of the TEMP pin. The
comparator CP1 monitors the existence of the NTC thermistor.
When the thermistor is removed, the TEMP pin voltage is pulled
FN9173 Rev 4.00
March 9, 2006
Page 11 of 17
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