CDH2D09 datasheet(31/44 Pages) MAXIM

31 / 44 page

PMIC with Integrated Charger and

Smart Power Selector for Handheld Devices

______________________________________________________________________________________

Charge Timer (CT)

As shown in Figure 7, a fault timer prevents the battery

from charging indefinitely. In prequalification and fast-

charge modes, the timer is controlled by the capaci-

tance at CT (CCT). The MAX8671X supports values of

CCT from 0.01µF to 1µF. Calculate the prequalification

and fast-charge times as follows (Table 4, Figure 8):

When the charger exits fast-charge mode, a fixed 15s

top-off mode is entered:

While in the constant-current fast-charge mode (Figure

6), if the MAX8671X reduces the battery charge current

due to its internal die temperature or large system

loads, it slows down the charge timer. This feature elim-

inates nuisance charge timer faults. When the battery

charge current is between 100% and 50% of its pro-

grammed fast-charge level, the fast-charge timer runs

at full speed. When the battery charge current is

between 50% and 20% of the programmed fast-charge

level, the fast-charge timer is slowed by 2x. Similarly,

when the battery charge current is below 20% of the

programmed fast-charge level, the fast-charge timer is

paused. The fast-charge timer is not slowed or paused

when the charger is in the constant voltage portion of

its fast-charge mode (Figure 6) where charge current

reduces normally.

Connect CT to AGND to disable the prequalification

and fast-charge timers. With the internal timers of the

MAX8671X disabled, an external device, such as a µP,

can control the charge time through the CEN input.

Setting the Charger Currents (CISET)

As shown in Table 5 and Figure 9, a resistor from

CISET to ground (RCISET) sets the maximum fast-

charge current (ICHGMAX), the charge current in pre-

qualification mode (IPQ), and the top-off threshold (ITO).

The MAX8671X supports values of ICHGMAX from

200mA to 1000mA. Select the RCISET as follows:

CISET

CHGMAX

=×

2000

TO = 15

=×

015

660

015

min

CCT (nF)

tPQ (min)

tFC (min)

100% to 50%

tFC (min)

50% to 20%

15.0

299

598

100

22.0

440

880

150

33.0

660

1320

220

48.4

968

1936

470

103.4

2068

4136

Table 4. Charge Times vs. CCT

CST1

CST2

CHARGING

STATE

Yes

Prequalification or

fast charge

Thermistor suspend

Timer fault

No input power or

top-off or

done

Table 3. Charge Status Outputs

Note: CST1 and CST2 are active-low, open-drain outputs. “0”

indicates that the output device is pulling low. “1” indicates

that the output is high impedance.

CHARGE, PREQUALIFICATION,

AND TOP-OFF CURRENT

vs. CHARGE SETTING RESISTOR

RCISET (k

Ω)

100

1000

015

ICHGMAX

IPQ

ITO

Figure 8. Programming Charge Current

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