Rainbow Electronics MAX8804Z - Manual (Page 7)

MAX8804Y/MAX8804Z
High-Voltage, Dual-Input, USB/AC
Adapter Chargers in 2mm x 3mm TDFN
Detailed Description
The MAX8804Y/MAX8804Z dual-input linear battery
chargers use voltage, current, and thermal-control loops
to charge and protect a single Li+ battery. When a Li+
battery with a cell voltage below 2.5V is inserted, the
MAX8804Z charger enters the prequalification stage
where it precharges that cell with 95mA (Figure 2). The
CHG indicator output is driven low to indicate entry into
the prequalification state. When battery voltage exceeds
2.5V, the charger soft-starts as it enters the fast-charge
stage. The MAX8804Y eliminates the prequalification
state and enters fast-charge when the battery is inserted.
In the MAX8804Y/MAX8804Z, the fast-charge current
level is programmed by a simple single-wire interface.
As the battery voltage approaches 4.2V, the charging
current is reduced. If the battery current drops below the
top-off current threshold, the CHG indicator goes high
impedance, signaling that the battery is fully charged.
The ICs then enter a constant voltage-regulation mode to
maintain the battery at full charge.
The MAX8804Y/MAX8804Z automatically select between
either a USB or AC adapter input source. The AC
adapter charge current is programmable from 400mA to
700mA in 50mA steps through a simple single-wire inter-
face. The USB charge current is programmable to 95mA,
380mA, or 475mA through the same interface.
DC AND USB OUTPUT CONTROL
LOGIC
CONTROL
DC
USB
BAT
SET
POK
CHG
USBPWR
4.15V TO 30V
4.15V TO 16V
TEMP
SENSOR
+105 °C
VOLTAGE
LOOP
BIAS
CIRCUIT
REF
GND
OVERVOLTAGE
PROTECTION
Li+
MAX8804Y
MAX8804Z
DC
POK
USB
POK
Figure 1. Functional Diagram
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