ISL6297_07 Datasheet, PDF (10/16 Pages) Intersil Corporation – Li-ion/Li Polymer Battery Charger

ISL6297
VIN
Short Circuit Test
Connection Verification
V2P9
DT
500ms
500ms
500ms
500ms
70ms
500ms
RED
GRN
LEDs
off
EN
VSEN
I_CHG
Red
Green
Yellow
off
4.4V
Trickle current
FIGURE 4. EVENT SEQUENCE AT POWER UP
Red
Charge Starts
Battery (+)
connection
verified
384 cycles
max.
Check if
BAT > 1V
If not: FAULT
EN
VSEN
I_CHG
V_IN
4.4V
500ms
Battery connected here, but voltage
remains above the battery detect
(falling) threshold
- Open battery detected
4.3V
70ms
Trickle current
Charge terminates. EN or
POR required before charge
sequence starts again
FIGURE 5. OPEN BATTERY DETECTED
Charge Current and R_IREF Selection
When the ISL6297 is used as a traditional linear charger, the
RIREF sets the constant charge current. When working with a
dual-mode, current-limited supply, the CC current is determined
by the supply limited current ILIM. IREF needs to be
programmed higher than ILIM and is used as an overcurrent
protection. Taking into account the tolerance of both the ILIM
and IREF, it is recommended the IREF be programmed at least
30% higher than the ILIM. IREF can be calculated by using the
following equation:
I_REF=
---⁰---^.--⁸----^V-----
R_IREF
×
10⁵ ( A )
(EQ. 3)
The trickle charge current is 10% of I_REF, that is,
I_Trickle=
---⁰---^.--⁸----^V-----
R_IREF
×
10⁴ (
A
)
(EQ. 4)
The ISL6297 has a comparator with a 50mV offset voltage to
ensure the input voltage is higher than the battery voltage
before charging starts (see the Block Diagram). This
condition, coupled with an R_DS(on) of about 400mΩ (max)
requires I_LIM be higher than 125mA. The upper limit for I_LIM
is 1.5A.
EOC Current and R_IMIN Selection
The EOC current level is programmed by the I_MIN pin and
can be calculated by the following equation:
I_MIN=
--⁰----^.-⁸----^V-----
R_IMIN
×
10⁴
(A)
(EQ. 5)
The EOC current has a programming range up to 400mA.
To qualify as an EOC condition, the battery voltage must be
above the recharge threshold given in the Electrical
Specification table and the charge current needs to drop
below the I_MIN level for 3 to 4 cycles of the internal oscillator.
10
FN9215.1
March 20, 2007