ISL6292DCRZ-T データシートの表示（PDF） - Renesas Electronics
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ISL6292DCRZ-T Datasheet PDF : 13 Pages
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ISL6292D
End-of-Charge (EOC) Current
The end-of-charge current IMIN sets the level at which the
charger indicates the end of the charge with the STAT1 and
STAT2 pins, as shown in Figure 4. The charger terminates at
this moment. The IMIN is set in two ways, by connecting a
resistor between the IMIN pin and ground, or by connecting the
IMIN pin to the V2P8 pin. When programming with the resistor,
the IMIN is set in the equation below.
IMIN = 10000 R-V----IR--M---E--I--FN-- = R---0--I-.-M-8---V-I--N--104A
(EQ. 6)
where RIMIN is the resistor connected between the IMIN pin
and the ground. When connected to the V2P8 pin, the IMIN is
set to 1/10 of IREF, except when the IREF pin is shorted to
GND. Under this exception, IMIN is 5mA.
Charge Current Thermal Foldback
Over-heating is always a concern in a linear charger. The
maximum power dissipation usually occurs at the beginning of
a charge cycle when the battery voltage is at its minimum but
the charge current is at its maximum. The charge current
thermal foldback function in the ISL6292D frees users from the
over-heating concern.
Figure 5 shows the current signals at the summing node of the
current error amplifier CA in the Block Diagram. IR is the
reference. IT is the current from the Temperature Monitoring
block. The IT has no impact on the charge current until the
internal temperature reaches approximately 100°C; then IT
rises at a rate of 1A/°C. When IT rises, the current control
loop forces the sensed current ISEN to reduce at the same
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.
IR
IT
ISEN
100OC Temperature
FIGURE 5. CURRENT SIGNALS AT THE AMPLIFIER CA INPUT
Usually the charge current should not drop below IMIN
because of the thermal foldback. For some extreme cases if
that does happen, the charger does not indicate end-of-charge
unless the battery voltage is already above the recharge
threshold.
2.8V Bias Voltage
The ISL6292D provides a 2.8V voltage for biasing the internal
control and logic circuit. This voltage is also available for
external circuits such as the NTC thermistor circuit. The
maximum allowed external load is 2mA.
NTC Thermistor
The ISL6292D uses two comparators (CP2 and CP3) to form a
window comparator, as shown in Figure 7. When the TEMP pin
voltage is “out of the window,” determined by the VTMIN and
VTMAX, the ISL6292D stops charging and indicates a fault
condition. When the temperature returns to the set range, the
charger re-starts a charge cycle. The two MOSFETs, Q1 and
Q2, produce hysteresis for both upper and lower thresholds. The
temperature window is shown in Figure 6.
3.0V
VTMIN (1.50V)
VTMIN-
(1.286V)
TEMP
Pin
Voltage
VTMAX+ (0.660V)
VTMAX (0.605V)
0V
Under
Temp
Over
Temp
FIGURE 6. CRITICAL VOLTAGE LEVELS FOR TEMP PIN
ISL6292D
2.8V
V2P8
R1
Battery
Removal
CP1 -
+
Under
Temp
CP2 -
+
VRMV
R2
RU
VTMIN
R3
To TEMP Pin
TEMP
Q1
Over
Temp
CP3 -
+
VTMAX
R4
RT
Q2
R5
GND
FIGURE 7. THE INTERNAL AND EXTERNAL CIRCUIT FOR
THE NTC INTERFACE
FN9166 Rev.0.00
July 2004
Page 10 of 13
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