Datasheet
MAX8600/MAX8601
Charge Current Selection
The maximum charging current from a supply connect-
ed to DC is programmed by an external resistor (R
SETI
)
connected from SETI to GND. Calculate the R
SETI
value
as follows:
R
SETI
= 1500 / I
CHARGE(MAX)
where I
CHARGE(MAX)
is in amps and R
SETI
is in ohms.
SETI can also be used to monitor the actual charge-
current level. The output voltage at SETI is proportional
to the charging current as follows:
V
SETI
= (I
CHARGE
x R
SETI
) / 1000
Note that the prequal current for both USB and DC
input operation is 1/10 of the fast-charge current set by
R
SETI
. Also, the top-off charge-current threshold for
both USB and DC input operation is set to 7.5% of the
fast-charge current set by R
SETI
.
I
PREQUAL
= 150 / R
SETI
I
TOP-OFF
= 112.5 / R
SETI
Timer Capacitor Selection
The MAX8600/MAX8601 contain timers for prequal,
fast-charge, and top-off operation. These time periods
are determined by the capacitance from CT to GND. To
set the charge times, calculate C
CT
as follows:
T
FASTCHARGE
= 334min x (C
CT
/ 0.068µF)
T
PREQUAL
= T
TOPOFF
= 34.8min x (C
CT
/ 0.068µF)
Note that when charging at 100mA from the USB input
(MAX8601), the fast-charge timer is inhibited. When THM
halts charging, the timers stop and hold their value.
Battery Temperature Control
The MAX8600/MAX8601 monitor battery temperature
through a negative TC thermistor which is in close ther-
mal contact with the battery. Select a thermistor resis-
tance that is 10kΩ at +25°C and has a beta of 3500.
The IC compares the resistance from THM to GND and
suspends charging when it is greater than 28.3kΩ or
less than 3.94kΩ, which translates to a temperature of
0°C to +50°C. Table 1 shows the nominal temperature
limits that result from a wide range of available thermis-
tor temperature curves. The curves are defined by the
following equation:
where β is the BETA term in Table 1.
Connect THM to GND to disable the temperature-con-
trol function. When R
THM
disables charging, all timers
pause and hold their value.
Capacitor Selection
Connect a 2.2µF ceramic capacitor from BAT to GND
for proper stability. Connect a 1µF ceramic capacitor
from DC to GND. If using the USB input for the
MAX8601, bypass USB to GND with a 1µF ceramic
capacitor. Use a larger input bypass capacitor for high
charging currents to reduce supply noise. All capaci-
tors should be X5R dielectric or better. Be aware that
some capacitors have large voltage coefficients and
should be avoided.
Thermal Considerations
The MAX8600/MAX8601 are in a thermally enhanced
TDFN package with an exposed paddle. Connect the
exposed paddle of the package to a large copper
ground plane to provide a thermal contact between the
device and the circuit board. The exposed paddle
transfers heat away from the device, allowing the IC to
charge the battery with maximum current, while mini-
mizing the increase in die temperature. Note that the
MAX8600/MAX8601s’ thermal-limit control allows the
charger to be tolerant of thermally restricted PC board
layouts that are sometimes unavoidable in compact
portable designs. With such non-optimal layouts, the
charger still operates, but may reduce charge current
to manage temperature rise.
RR
T
TCe
=
+
⎛
⎝
⎜
⎞
⎠
⎟
⎛
⎝
⎜
⎞
⎠
⎟
⎡
⎣
⎢
⎤
⎦
⎥
⎧
⎨
⎪
⎩
⎪
⎫
⎬
⎪
⎭
⎪
°×
−
25
1
273
1
298
β
Single-/Dual-Input 1-Cell Li+ Chargers with
OVP Protection and Programmable Charge Timer
8 _______________________________________________________________________________________
THERMISTOR BETA 3000 3250 3500 3750
Resistance at +25°C 10,000Ω 10,000Ω 10,000Ω 10,000Ω
Resistance at +50°C 4587.78Ω 4299.35Ω 4029.06Ω 3775.75Ω
Resistance at 0°C 25,140.55Ω 27,148.09Ω 29,315.94Ω 31,656.90Ω
Nominal Hot Trip Temperature +55.14°C +52.60°C +50.46°C +48.63°C
Nominal Cold Trip Temperature -3.24°C -1.26°C +0.46°C +1.97°C
Table 1. Fault Temperatures for Different Thermistors