MAX8804Y Datasheet, PDF (12/15 Pages) Maxim Integrated Products – High-Voltage, Dual-Input, USB/AC Adapter Chargers in 2mm x 3mm TDFN

High-Voltage, Dual-Input, USB/AC
Adapter Chargers in 2mm x 3mm TDFN
Power-OK Monitor (POK)
The MAX8804Y/MAX8804Z contain an open-drain POK
output that goes low when a valid input source is
detected at either DC or USB. A valid input source is
one whose voltage is greater than 4.15V and exceeds
the battery voltage by 250mV. After a valid input has
been established, charging is sustained with inputs as
low as 3.5V as long as the input voltage remains above
the battery voltage by at least 40mV. POK status is
maintained regardless of SET status.
When the MAX8804Y/MAX8804Z are used in conjunc-
tion with a µP, connect a pullup resistor between POK
and the logic I/O voltage to indicate power-OK to the
µP. Alternatively, POK can sink up to 5mA for an LED
power-OK indicator.
USB Power Status Output (USBPWR)
USBPWR is internally pulled low when V_USB > V_UVLO
and V_USB - V_BAT > 250mV. Otherwise, it is high imped-
ance. USBPWR indicates the USB input presence
regardless of SET status and charger status.
When the MAX8804Y/MAX8804Z are used in conjunction
with a µP, connect a pullup resistor between USBPWR
and the logic I/O voltage to indicate USB power status
to the µP. Alternatively, USBPWR can sink up to 5mA
for an LED USB power status indicator.
Applications Information
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, bypass USB to GND
with a 1µF ceramic capacitor. Use a larger input bypass
capacitor for high charging currents to reduce supply
noise. All capacitors should be X5R dielectric or better.
Be aware that some capacitors have large voltage and
temperature coefficients and should be avoided.
Thermal Considerations
The MAX8804Y/MAX8804Z are available in a thermally
enhanced TDFN package with an exposed paddle.
Connect the exposed paddle to a large copper ground
plane to provide a thermal contact between the device
and the PCB for increased power dissipation. The
exposed paddle transfers heat away from the device,
allowing the IC to charge the battery with maximum cur-
rent, while minimizing the die temperature increase.
Input Sources
The MAX8804Y/MAX8804Z operate from well-regulated
input sources. The operating input voltage range is
4.15V to 7V. The device survives DC input supply volt-
ages up to 30V and USB input source voltages up to
16V without damage to the IC. If the input voltage is
greater than 7.5V (typ), the IC stops charging. An
appropriate power supply must provide at least 4.2V
plus the voltage drop across the internal pass transistor
when sourcing the desired maximum charging current:
V_IN(MIN) > 4.2V + I_CHARGE(MAX) x R_ON
where R_ON is the input-to-BAT resistance (typically
0.55Ω for DC or 0.65Ω for USB). Failure to meet this
requirement results in an incomplete charge or
increased charge time.
Application Circuits
Stand-Alone Li+ Charger
The MAX8804Y/MAX8804Z provide a complete Li+
charging solution. The Typical Application Circuit
shows the MAX8804Y/MAX8804Z as a stand-alone Li+
battery charger. The LED indicates when either fast-
charge or prequalification has begun. When the battery
is fully charged, the LED turns off.
Microprocessor-Interfaced Li+ Charger
Figure 5 shows the MAX8804Y/MAX8804Z as a µP-
interfaced Li+ battery charger. The µP drives SET to
enable/disable DC/USB mode charging. CHG can be
used to detect the charge status of a battery.
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