MAX8677AETG+T Maxim Integrated Products, MAX8677AETG+T Datasheet - Page 17

• Manufacturer Part Number: MAX8677AETG+T
• Description: IC USB/AC ADP CHARGER 24-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8677AETG+T

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.1 V ~ 6.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 MAX8677A 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 MAX8677A automat-
ically 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. 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 filter-
ing of the charge-current monitor is necessary, add a
resistor of 100kΩ or more between ISET and the filter
capacitor to preserve charger stability. See Figure 6.
Note that the actual charge current can be less than
the set fast-charge current when the charger enters
voltage mode or when charge current is reduced by
the input current limiter or thermal limiter. This prevents
the charger from overloading the input source or over-
heating 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 and then enters the DONE state in which charg-
ing stops. The termination current threshold (I
set by TSET to a percentage of the fast-charge current:
V
Connect TSET to GND for I
ISET
I
CHGMAX
CHGMAX
= I
CHG
CHGMAX
= 2000 x 1.5V/R
x 1.5V/I
Monitoring the Charge Current
is the set fast-charge current and I
1.5A Dual-Input USB/AC Adapter Charger
______________________________________________________________________________________
Setting the Charge Current
CHGMAX
value by considering the char-
Charge Enable ( CEN )
Charge Termination
TERM
ISET
= I
CHG
= I
= 3000/R
CHGMAX
x R
ISET
ISET
TERM
/2000
x 5%
CHG
) is
and Smart Power Selector
When the charger enters DONE 15s later, the DONE
output goes low. Note that if charge current falls to
I
charger does not enter DONE. For the charger to enter
DONE, the charge current must be less than I
charger must be in voltage mode, and the input or ther-
mal limiter must not be reducing the charge current.
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.
When the MAX8677A is used 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 indicator.
DONE is an open-drain, active-low output that goes low
when charging is complete. The charger enters its
DONE state 15s after charge current falls to the
Figure 6. Monitoring the Charge Current with the ISET Voltage
TERM
Connect TSET to VL for I
Leave TSET open for I
1.5
0
as a result of the input or thermal limiter, the
DISCHARGING
0
CHARGE CURRENT WITH V
MONITORING THE BATTERY
BATTERY CHARGING CURRENT (A)
V
ISET
Charge Done Output ( D D O O N N E E )
Charge Status Outputs
TERM
=
TERM
R
2000
ISET
= I
Charge Output ( C C H H G G )
= I
x I
CHG
CHGMAX
CHGMAX
ISET
2000 (1.5V / R
x 10%
x 15%
TERM
, the
ISET
17
)