MAX8601ETD(2005) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX8601ETD
(Rev.:2005)

Single-/Dual-Input 1-Cell Li+ Chargers with OVP Protection and Programmable Charge Timer

Maxim Integrated 

Single-/Dual-Input 1-Cell Li+ Chargers with

OVP Protection and Programmable Charge Timer

Table 1. Fault Temperatures for Different Thermistors

THERMISTOR BETA

Resistance at +25°C

Resistance at +50°C

Resistance at 0°C

Nominal Hot Trip Temperature

Nominal Cold Trip Temperature

3000

10,000Ω

4587.78Ω

25,140.55Ω

+55.14°C

-3.24°C

3250

10,000Ω

4299.35Ω

27,148.09Ω

+52.60°C

-1.26°C

3500

10,000Ω

4029.06Ω

29,315.94Ω

+50.46°C

+0.46°C

3750

10,000Ω

3775.75Ω

31,656.90Ω

+48.63°C

+1.97°C

Charge Current Selection

The maximum charging current from a supply connect-

ed to DC is programmed by an external resistor (RSETI)

connected from SETI to GND. Calculate the RSETI value

as follows:

RSETI = 1500 / ICHARGE(MAX)

where ICHARGE(MAX) is in amps and RSETI 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:

VSETI = (ICHARGE x RSETI) / 1000

Note that the prequal current for both USB and DC

input operation is 1/10 of the fast-charge current set by

RSETI. 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 RSETI.

IPREQUAL = 150 / RSETI

ITOP-OFF = 112.5 / RSETI

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 CCT as follows:

TFASTCHARGE = 334min x (CCT / 0.068µF)

TPREQUAL = TTOPOFF = 34.8min x (CCT / 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:

RT

= R25°C ×

e⎧⎨⎪⎩⎪β⎡⎣⎢⎛⎝⎜

1⎞

T + 273⎠⎟

−

⎛

⎝⎜

1

298

⎞

⎠⎟

⎤⎫⎪

⎦⎥⎬⎭⎪

where β is the BETA term in Table 1.

Connect THM to GND to disable the temperature-con-

trol function. When RTHM 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.

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