Rainbow Electronics MAX8903A - Manual (Page 18)

MAX8903A
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
18 ______________________________________________________________________________________
charging resumes and the charge timer continues from
where it left off. Connecting THM to GND disables the
thermistor monitoring function. Table 4 lists the fault
temperature of different thermistors.
Since the thermistor monitoring circuit employs an
external bias resistor from THM to VL (R
TB , Figure 7),
the thermistor is not limited only to 10k
Ω (at +25°C).
Any resistance thermistor can be used as long as the
value is equivalent to the thermistor’s +25°C resistance.
For example, with a 10k
Ω at +25°C thermistor, use
10k
Ω at R
TB , and with a 100k
Ω at +25°C thermistor,
use 100k
Ω .
For a typical 10k
Ω (at +25°C) thermistor and a 10kΩ
R TB resistor, the charger enters a temperature suspend
FAULT
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = LOW
I CHG = 0mA
PREQUALIFICATION
UOK AND/OR DOK = LOW
CHG = LOW
FLT = HIGH IMPEDANCE
0 < V BAT < 3V
I CHG
≤ I
CHGMAX /10
DONE
UOK AND/OR DOK = 0
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
4.1V < V BAT < 4.2V
I CHG = 0mA
FAST-CHARGE
UOK AND/OR DOK = LOW
CHG = LOW
FLT = HIGH IMPEDANCE
3V < V BAT < 4.2V
I CHG
≤ I
CHGMAX
NOT READY
UOK AND DOK = HIGH IMPEDANCE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
I CHG = 0mA
TIMER > t PREQUAL
V BATT > 3.0V
RESET TIMER
V BATT < 2.82V
RESET TIMER = 0
I CHG < I TERM
AND V BAT = 4.2V
AND THERMAL
OR INPUT LIMIT
NOT EXCEEDED;
RESET TIMER
I CHG > I TERM
RESET TIMER
V BAT < 4.1V
RESET TIMER
TIMER > 15s
UOK AND/OR DOK = LOW
CEN = 0
RESET TIMER
CEN = HI OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
ANY STATE
TOGGLE CEN OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
TIMER > t FSTCHG
(TIMER SLOWED BY 2x IF
I
CHG < I CHGMAX /2, AND
PAUSED IF I
CHG
< I
CHGMAX
/5 WHILE V
BAT
< 4.2V)
TOP-OFF
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
VBAT = 4.2V
I CHG = I TERM TEMPERATURE SUSPEND
I CHG = 0mA
UOK OR DOK PREVIOUS STATE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
ANY CHARGING
STATE
THM NOT OK
TIMER SUSPEND THM OK
TIMER RESUME
V BATT < 2.8V
RESET TIMER
Figure 6. MAX8903A Charger State Flow Chart