ISL6293_06 Datasheet, PDF (6/8 Pages) Intersil Corporation – Li-ion/Li Polymer Battery Charger Accepting Two Power Sources

ISL6293
CHG (Pin 4)
Charge indication pin. When the charge current from the
cradle input during the constant current mode falls to below
8% of the programmed reference current by the ICDL pin or
the charge current from the USB input is below 10% of the
programmed charge current, the open-drain MOSFET is
turned off. The pin will be pulled to logic HIGH by an external
resistor to indicate the End Of Charge.
EN (Pin 5)
Enable logic input. Connect to LOW or leave floating to
enable the charger.
IUSB (Pin 6)
The IUSB pin programs the USB charge current. This pin is
regulated to 0.8V. The current flowing out of this pin is
mirrored to the USB charge current control reference. When
the USBP pin is connected to logic HIGH, the typical USB
charge current can be found as:
I_USB
=
45000
⋅
--^V----^R----^E----^F---
R_IUSB
=
45000
×
---⁰---^.--⁸----^V-----
R_IUSB
(
A
)
The R_IUSB has a programming range of 80kΩ to 103kΩ,
thus the USB current has a nominal value ranging from
350mA to 450mA.
When the USBP pin is driven to logic LOW, the charge
current is approximately 1/5 of the above value.
USBP (Pin 7)
USB port selection logic input. When this pin is left floating or
driven to logic LOW, the USB port is regarded as a
low-power port, in such case the charge current is 100mA
maximum. When this pin is driven to logic HIGH, the USB
port is considered a high-power port, and the charge current
is 500mA maximum. The ratio of the charge current when
this pin is HIGH or LOW is fixed at approximately 5:1.
GND (Pin 8)
System ground.
ICDL (Pin 9)
The ICDL pin has two functions. The first function is to
program the cradle charge current during the constant-
current phase. The voltage of this pin is 1.20V during the
constant-current phase of the cradle input charger. The
constant-current is programmed by the following equation:
I_CDL=
-¹----^.-²----⁰---^V----
R_ICDL
⋅
r
a
t
i
o
(A)
where R_ICDL is the resistor connected to the ICDL pin (see
Typical Application). The ratio is given by the following table
and curve.
R_ICDL (kΩ)
Ratio
TABLE 1. RATIO vs. R_ICDL
1.5
2.2
3.0
3.9
1291
1216 1155 1122
4.6
1088
It is recommended that the charge current be programmed
in the range of 300mA to 1A.
1280
1250
1220
1190
1160
1130
1100
1070
1
2
3
4
5
R_ICDL (kΩ)
FIGURE 1. THE RATIO USED IN THE CHARGE CURRENT
CALCULATION vs. R_ICDL
The second function of the ICDL pin is to monitor the actual
charge current. The voltage of this pin, V_ICDL, is proportional
to the actual charge current, I_CHG, in either the USB or the
cradle charger. When the cradle charger or the USB charger
is working with USBP connected to logic HIGH, the ICDL pin
voltage is given by the following equation:
V_ICDL=
1_----._--2_---0_----V_--
I_CDL
⋅
I_C
H
G
=
R_{-----I--C----D----L-----}⋅_---I_{--C----H----G---}
ratio
where the ratio has the same value given in Table 1.
The cradle charge current should be programmed equal or
higher than the USB current; otherwise, the ICDL pin voltage
will be higher than 1.20V during the constant current phase
when the USB charger is working. The charger still works
properly but the accuracy of the current monitoring voltage
degrades and saturates at approximately 2.1V.
When the USB charger is working with the USBP pin
connected to logic LOW, the ICDL pin voltage is
approximately five times of the above equation.
BAT (Pin 10)
Charger output pin. Connect this pin to the battery pack or
the battery cell. A 1µF or larger value ceramic capacitor is
recommended for decoupling. The charger relies on the
battery for stability so a battery should always be connected
to the BAT pin.
6
FN9180.1
January 4, 2006