MAX8903BETI+ Maxim Integrated Products, MAX8903BETI+ Datasheet - Page 19

• Manufacturer Part Number: MAX8903BETI+
• Description: IC DC/DC CHARGER LI+ 2A 28-TQFN
• Manufacturer: Maxim Integrated Products
• Series: Smart Power Selector™r

Specifications of MAX8903BETI+

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.1 V ~ 16 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

again as long as the SYS load current is less than the
set current limit.
When the charger is turned on, the charge current ramps
from 0A to the ISET current value in typically 1.0ms.
Charge current also soft-starts when transitioning to fast-
charge from prequal, when the input power source is
switched between USB and DC, and when changing the
USB charge current from 100mA to 500mA with the IUSB
logic input. There is no di/dt limiting, however, if R
changed suddenly using a switch.
While a valid input source is present, the battery charg-
er attempts to charge the battery with a fast-charge
current determined by the resistance from ISET to
GND. Calculate the R
following equation:
The voltage from ISET to GND is a representation of the
battery charge current and can be used to monitor the
current charging the battery. A voltage of 1.5V repre-
sents the maximum fast-charge current.
If necessary, the charge current is reduced automati-
cally to prevent the SYS voltage from dropping.
Therefore, a battery never charges at a rate beyond the
capabilities of a 100mA or 500mA USB input, or over-
loads an AC adapter. See Figure 5.
When V
qual mode and the battery charges at 10% of the maxi-
Figure 5. Monitoring the Battery Charge Current with the
Voltage from ISET to GND
V
ISET
1.5
0
BAT
(V)
R
DISCHARGING
ISET
is below V
= 1200V/I
______________________________________________________________________________________
CHARGE CURRENT WITH V
MONITORING THE BATTERY
BATTERY CHARGING CURRENT (A)
0
ISET
BATPQ
2A 1-Cell Li+ DC-DC Chargers for USB
CHGMAX
Monitoring Charge Current
resistance according to the
, the charger enters pre-
ISET
Battery Charger
1200V/R
ISET
ISET
is
mum fast-charge rate until the voltage of the deeply
discharged battery recovers. When the battery voltage
reaches V
of the maximum fast-charge current, the charger enters
the DONE state. The charger restarts a fast-charge
cycle if the battery voltage drops by 100mV.
When the charge current falls to the termination thresh-
old (I
ing is complete. Charging continues for a brief 15s
top-off period and then enters the DONE state where
charging stops.
Note that if charge current falls to I
the input or thermal limiter, the charger does not enter
DONE. For the charger to enter DONE, charge current
must be less than I
age mode, and the input or thermal limiter must not be
reducing charge current.
CHG is an open-drain, active-low output that indicates
charger status. CHG is low when the battery charger is
in its prequalification and fast-charge states. CHG goes
high impedance if the thermistor causes the charger to
go into temperature suspend mode.
When used in conjunction with a microprocessor (μP),
connect a pullup resistor between CHG and the logic
I/O voltage to indicate charge status to the μP.
Alternatively, CHG can sink up to 20mA for an LED
charge indicator.
FLT is an open-drain, active-low output that indicates
charger status. FLT is low when the battery charger has
entered a fault state when the charge timer expires.
This can occur when the charger remains in its prequal
state for more than 33 minutes or if the charger remains
in fast-charge state for more than 660 minutes (see
Figure 6). To exit this fault state, toggle CEN or remove
and reconnect the input source.
When used in conjunction with a microprocessor (μP),
connect a pullup resistor between FLT and the logic I/O
voltage to indicate charge status to the μP.
Alternatively, FLT can sink up to 20mA for an LED fault
indicator. If the FLT output is not required, connect FLT
to ground or leave unconnected.
A fault timer prevents the battery from charging indefi-
nitely. The fault prequal and fast-charge timers are con-
trolled by the capacitance at CT (C
TERM
and Adapter Power
BATREG
) and the charger is in voltage mode, charg-
and the charge current drops to 10%
TERM
, the charger must be in volt-
Charge Status Outputs
Charge Termination
Charge Output (CHG)
CT
Fault Output (FLT)
TERM
).
Charge Timer
as a result of
19