ISL6293 Datasheet, PDF (7/8 Pages) Intersil Corporation – Li-ion/Li Polymer Battery Charger Accepting Two Power Sources

ISL6293
Input Auto Selection
The charger selects only one power source to charge the
battery. When the CRDL input is higher than both the POR
threshold and the battery voltage, CRDL is the power
source. When this condition is not true, then the USB input is
selected as the power source. If the CRDL input happens to
have a voltage below the battery voltage but the USB input
has a voltage higher than the battery voltage, then the USB
input is used to charge the battery. The control circuit always
breaks both internal power devices before switching in one
power source to avoid any simultaneous conduction of both
power MOSFETs.
When the BAT pin voltage is below 1.7V, the charger selects
the CRDL input as the power source. Hence, if the USB
input is powered, the charger will not charge the battery.
USB Charge Current
When the USB port is the power source, the charge current
is programmed by the logic input USBP pin. When the USBP
is driven to logic LOW, the charge current is set to 90mA
(when R_IUSB is 80kΩ). When the USBP is driven to logic
HIGH, the charge current is set to 450mA (when R_IUSB is
80kΩ). The USBP is equivalent to a logic LOW when left
floating. Typically the P-channel MOSFET for the USB input
has an r_DS(ON) of 700mΩ at room temperature. With a
500mA charge current, the typical head room is 350mV. If
the input voltage drops to a level that the voltage different
between the USB pin and the BAT pin is less than 350mV,
the r_DS(ON) becomes a limiting factor of the charge current;
and the charge current will reduce to a lower level in this case.
Cradle Charge Current
The cradle charge current is programmed with the external
resistor connected between the ICDL pin and the GND pin.
The current can be calculated with the equation given in the
ICDL pin description. The typical P-channel MOSFET for the
CRDL input is 700mΩ at room temperature. The actual
charge current will be limited by several factors, for example,
the programmed ICDL, the thermal limit, and the r_DS(ON).
Floating Charge Voltage
The floating voltage during the constant voltage mode is
4.2V. The floating voltage has 1% accuracy over the ambient
temperature range of -40°C to 70°C. No leakage current
from any of the two power MOSFETs will cause the battery
voltage to drift to a higher level.
Trickle Charge Current
When the battery voltage is below the minimum battery
voltage V_MIN given in the electrical specification, the charger
operates in a trickle/preconditioning mode. If power comes
from the cradle, the trickle mode current is
I_TRICKLE=
-¹----^.-²----⁰---^V----
R_ICDL
⋅
100
(A)
The trickle current is 45mA if the power comes from the USB
port with R_IUSB = 80kΩ.
End-of-Charge Indication
The CHG pin outputs a logic HIGH by turning off the internal
open-drain MOSFET when the charge current falls below
8% of the constant current mode current for the cradle
charger or 10% for the USB charger. The charger, however,
does not turn off as long as an input power source is
attached.
Power Presence Indication
When either the USB or the cradle input voltage is above the
POR level, the PPR pin outputs a logic LOW signal to
indicate the presence of input power.