Datasheet

19Maxim Integrated
1.2A Switch-Mode Li+ Chargers with ±22V Input
Rating and JEITA Battery Temperature Monitoring
MAX8900A/MAX8900B/MAX8900C
to enable the MAX8900_. CEN has an internal 200kI
pulldown resistor. When disabled, the MAX8900_ supply
current is reduced, the step-down converter high-side and
low-side switches are off, and the AVL is disabled.
In many systems, there is no need for the system control-
ler (typically a microprocessor (FP)) to disable the char-
ger because the MAX8900_ independently manages the
charger. In these situations, CEN can be connected to
ground or left unconnected. Note: if CEN is permanently
connected to ground or left unconnected, the input
power must be cycled to escape from a timer fault state
(see Figures 7 and 8 for more information).
V
IN
must be greater than V
UVLO-RISING
for the MAX8900_
to operate when CEN is pulled low. For example, if CEN is
low and the MAX8900_ is operating with V
UVLO-FALLING
< V
IN
< V
UVLO-RISING
, then toggling CEN results in a
nonoperating condition.
Charger States
The MAX8900_ utilizes several charging states to safely
and quickly charge batteries as shown in Figure 7.
Figure 6 shows an exaggerated view of a Li+/Li-Poly
battery progressing through the following charge states
when the die and battery are close to room temperature:
dead battery è prequalification è fast-charge è top-off
è done.
Figure 6. Li+/Li-Poly Charge Profile
V
PQUTH
V
BATREG
I
CHG P
I
SET
I
DBAT +
I
PQ
I
DBAT
0
I
PQ
V
PQLTH
V
DBAT
TIME
TIME
BATTERY CHARGE CURRENT BATTERY VOLTAGE
DEAD
BATTERY
DEAD BATTERY +
PREQUALIFICATION PREQUALIFICATION
FAST-CHARGE
(CONSTANT CURRENT)
FAST-CHARGE
(CONSTANT VOLTAGE)
TOP-OFF
DONE