MAX8934BETI+T Maxim Integrated Products, MAX8934BETI+T Datasheet - Page 23

• Manufacturer Part Number: MAX8934BETI+T
• Description: IC BATTERY CHARGER DUAL 28TQFN
• Manufacturer: Maxim Integrated Products
• Series: Smart Power Selector™r

Specifications of MAX8934BETI+T

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 4.1 V ~ 6.6 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

age where charge current starts tapering down. When
charge current decreases to 10% of the fast-charge
current, the charger enters a brief 15s top-off, (60min
for the MAX8934B and MAX8934D) and then charging
stops. If the battery voltage subsequently drops below
the recharge threshold, charging restarts and the timers
reset.
When CEN is low, the charger is on. When CEN is high,
the charger turns off. CEN does not affect the SYS out-
put. In many systems, there is no need for the system
controller (typically a microprocessor) to disable the
charger, because the MAX8934_ Smart Power Selector
circuitry independently manages charging and adapter/
battery power hand-off. In these situations, CEN can be
connected to ground.
ISET adjusts charge current to match the capacity of the
battery. A resistor from ISET to ground sets the maximum
fast-charge current:
Determine the I
acteristics of the battery. It is not necessary to limit the
charge current based on the capabilities of the expected
AC adapter/USB charging input, the system load, or
thermal limitations of the PCB. The MAX8934_ automati-
cally adjusts the charging algorithm to accommodate
these factors.
In addition to setting the charge current, ISET can also
be used to monitor the actual current charging the bat-
tery. See Figure 4. The ISET output voltage is:
where I
is the actual battery charge current. A 1.5V output indi-
cates the battery is being charged at the maximum set
fast charge current; 0V indicates no charging. This volt-
age is also used by the charger control circuitry to set
and monitor the battery current. Avoid adding more than
10pF capacitance directly to the ISET pin. If filtering of
the charge-current monitor is necessary, add a resistor
of 100kI or more between ISET and the filter capacitor
to preserve charger stability.
Note that the actual charge current can be less than the
set fast-charge current when the charger enters voltage
mode or when the input current limiter or thermal limiter
Dual-Input Linear Chargers, Smart Power Selector
V
ISET
with Advanced Battery Temperature Monitoring
I
CHGMAX
CHGMAX
= I
CHG
= 2000 x 1.5V/R
CHGMAX
x 1.5V/I
is the set fast-charge current and I
Monitoring the Charge Current
______________________________________________________________________________________
Setting the Charge Current
CHGMAX
value by considering the char-
Charge Enable (CEN)
ISET
= I
CHG
= 3000V/R
x R
ISET
ISET
/2000
CHG
reduces charge current. This prevents the charger from
overloading the input source or overheating the system.
When the charge current falls to the termination thresh-
old and the charger is in voltage mode, charging is
complete. Charging continues for a brief 15s top-off
period (60min for the MAX8934B and MAX8934D) and
then enters the DONE state where charging stops. The
DONE current threshold (I
charge current setting. Note that if charge current falls
to I
charger does not enter the DONE state. For the charger
to enter the DONE state, the charge current must be
less than I
and the input or thermal limiter must not be reducing the
charge current. The charger exits the DONE state, and
fast-charge resumes if the battery voltage subsequently
drops 104mV or if CEN is cycled.
CHG is an open-drain, active-low output that is low dur-
ing charging. CHG is low when the battery charger is in
its prequalification and fast-charge states. When charge
current falls to the charge termination threshold and the
charger is in voltage mode, CHG goes high impedance.
CHG goes high impedance if the thermistor causes the
charger to enter temperature suspend mode.
Figure 4. Monitoring the Battery Charge Current with V ISET
V
ISET
1.5
0
DONE
DISCHARGING
as a result of the input or thermal limiter, the
TERM
, the charger must be in voltage mode,
BATTERY CHARGING CURRENT (A)
CHARGE CURRENT WITH V
0
MONITORING THE BATTERY
DONE
Charge Status Outputs
Charge Termination
) is set to 10% of the fast-
Charge Output (CHG)
ISET
2000 (1.5V/R ISET )
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