ISL6292BCR Datasheet, PDF (9/12 Pages) Intersil Corporation – Complete Charger for Single-Cell Li-ion Batteries

ISL6292B
BAT
R1
10Ω
VSEN
R2
-
VA
+
V_REF
R3
Q1
Enable
FIGURE 5. THE INTERNAL VOLTAGE FEEDBACK CIRCUIT
C_TIME is the timing capacitor shown in the Typical
Application circuit. A 1nF capacitor leads to 14 minutes of
TIMEOUT. For example, a 15nF capacitor sets the
TIMEOUT to be 3.5 hours. The charger is terminated when
the TIMEOUT is reached.
The trickle mode charge has a time limit of 1/8 TIMEOUT. If
the battery voltage does not reach V_MIN within that limit, a
TIMEOUT fault is issued and the charger latches up. The
charger stays in trickle mode for at least 15 cycles of the
internal oscillator and, at most, 1/8 of TIMEOUT.
Recharge Threshold
The charger terminates when the TIMEOUT limit expires.
After the termination, if the battery is below the recharge
threshold given in the Electrical Specification table, the
charger starts a re-charge cycle.
LED Indications
RED and GRN are two open-drain outputs that directly drive
a tri-color LED. At the moment when the power is applied or
when the charger is enabled through the EN pin, the charger
starts to charge and the RED indication pin outputs a low
impedance to drive a red LED. Once the charge finishes
(either when the EOC condition is qualified or when the
TIMEOUT completes), the GRN pin turns on to drive a green
LED and the red LED is off. The green LED remains on
unless the input power is recycled, or when the EN pin is
toggled, or a fault case happens. When a recharge occurs,
the indication remains in green.
When a fault case happens, both the RED and the GRN pins
are on to indicate a yellow color. If the FAULT is a TIMEOUT
fault, the yellow indication is latched and can only be reset
through the EN pin or the input power. If the FAULT is an
ambient temperature FAULT, the charger restarts after the
fault condition is removed. When not powered or when not
enabled, both LEDs are off. Table 1 summarizes the LED
indications.
9
Under
Temp ^CP1 _-
+
Over
T e mp
CP2
-
+
2.9V
V2P9
R1
V_{TM IN}
100K
To TEMP Pin
R2
75K
TEMP
R_U
Q1
V_{TM AX}
R3
25K
R_T
Q2
R4
4K
CHG
DT
Q3
R_D
GND
FIGURE 6. THE INTERNAL AND EXTERNAL CIRCUIT FOR
THE NTC INTERFACE
TABLE 1. LED INDICATION SUMMARY
STATUS
RED GRN INDICATION
Charging
L H Red
Full Charge (EOC), or recharging H L Green
Trickle TIMEOUT Error
L L Yellow (Latched)
Over/Under Ambient Temperature L L Yellow
No Battery
H H Off
VSEN Pin
The VSEN pin allows remote sensing of the battery voltage
to minimize the resistive voltage drop between the charger
output and the battery positive terminal. Figure 5 shows the
internal voltage feedback circuit. In applications that the
remote sense pin goes through a connector, a local low-
value resistor is recommended, as the R₁ shown in Figure 5,
in case the connector has bad contact. The sum of R₂ and
R₃ is 75kΩ, therefore, a 10Ω R₁ is negligible in output
voltage accuracy.
Ambient Temperature Sensing
The TEMP pin is used to set the ambient temperature range
that allows charging the battery. Typically, an NTC (negative
temperature coefficient) resistor is mounted on the printed
circuit board (PCB) to monitor the ambient temperature. Due
to the self-heating of the PCB during charging, the ISL6292B
provides the DT pin to set a higher temperature threshold
after the charger starts.
Figure 6 shows the internal circuit for the ambient
temperature sensing function. The two comparators form a
window comparator whose high-threshold is V_TMIN and low-
threshold is V_TMAX. These two thresholds are given in the
Electrical Specifications. The two MOSFETs (Q1 and Q2)
FN9139 .1
April 19, 2005