High-Voltage, Dual-Input, USB/AC
Adapter Chargers in 2mm x 3mm TDFN
Power-OK Monitor (POK)
The MAX8804W/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.
www.DWathaeShnetehte4UM.cAomX8804W/MAX8804Y/MAX8804Z are used
in conjunction 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 VUSB > VUVLO
and VUSB - VBAT > 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.
Battery Pack Dectection Input
(DETBAT, MAX8804W Only)
DETBAT is pulled up to an internal 3V supply through a
63kΩ resistor. Driving DETBAT low or connecting it to
GND allows SET to control the charger. When DETBAT
is left unconnected, the MAX8804W enters shutdown.
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.
The MAX8804W/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 maxi-
mum current, while minimizing the die temperature
The MAX8804W/MAX8804Y/MAX8804Z operate from
well-regulated input sources. The operating input volt-
age range is 4.15V to 7V. The device survives DC input
supply voltages up to 30V and USB input source volt-
ages up to 16V without damage to the IC. If the input
voltage is greater than 7.5V (typ), the IC stops charg-
ing. An appropriate power supply must provide at least
4.2V plus the voltage drop across the internal pass
transistor when sourcing the desired maximum charg-
VIN(MIN) > 4.2V + ICHARGE(MAX) x RON
where RON 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.
Stand-Alone Li+ Charger
The MAX8804W/MAX8804Y/MAX8804Z provide a com-
plete Li+ charging solution. The Typical Application
Circuit shows the MAX8804W/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 MAX8804W/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.
Layout and Bypassing
Connect the input capacitors as close as possible to
the IC. Provide a large copper GND plane to allow the
exposed paddle to sink heat away from the IC. Connect
the battery to BAT as close as possible to the IC to pro-
vide accurate battery voltage sensing. Make all high-
current traces short and wide to minimize voltage
drops. A sample layout is available in the MAX8804Z
evaluation kit to speed designs.