19-2912; Rev 0; 7/03
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
General Description
Features
The MAX1874 charges a single-cell Li+ battery from
both USB and AC adapter sources. It also includes bat-
tery-to-input power switchover, so the system can be
powered directly from the power source rather than
from the battery.
ꢀ Charge from USB* or AC Adapter
ꢀ Automatic Switchover to AC Adapter
ꢀ Thermal Limiting Simplifies Board Design
ꢀ Small, High-Power 16-Pin Thin QFN Package
ꢀ Input Protection Up to 18V
In its simplest application, the MAX1874 needs no
external MOSFET or diodes, and accepts input volt-
ages up to 6.5V; however, DC input overvoltage protec-
tion up to 18V can be added with a single SOT PFET.
ꢀ Soft-Start
ꢀ Automatic Battery-to-Input Load Switch
*Protected by U.S. Patent #6,507,172.
On-chip thermal limiting simplifies PC board layout and
allows optimum charging rate without the thermal limits
imposed by worst-case battery and input voltage. When
the MAX1874 thermal limit is reached, the charger does
not shut down but simply reduces charging current.
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
Ambient or battery temperature can be monitored with
an external thermistor. When the temperature is out of
range, charging pauses.
MAX1874ETE -40 C to +85 C 16 Thin QFN 5mm x 5mm
Typical Operating Circuit
Other features include a CHG output to indicate when
battery current tapers below a predetermined level. DC
power-OK (DCOK), USB power-OK (UOK), and power-
on (PON) outputs indicate when valid power is present.
These outputs drive logic or power-selection MOSFETs
to disconnect the charging sources from the load and
to protect the MAX1874 from overvoltage.
DC INPUT
DC
PON
MAX1874
The MAX1874 contains no logic for communication with
the USB host. It must receive instructions from a local
microcontroller. The MAX1874 is available in a 16-pin
5mm ✕ 5mm thin QFN package and operates over the
-40°C to +85°C temperature range.
DCOK
DCLV
BATT
Li+
CELL
UOK
USB
Applications
CHG
USEL
EN
USB INPUT
TO REF
PDAs
Cell Phones
500mA
100mA
Wireless Appliances Digital Cameras
DCI
Pin Configuration
REGULATOR
REF
TOP VIEW
16 15 14 13
THRM
GND
DCLV
1
2
3
4
12 USB
11 BYP
10 PGND
DC
CHG
NTC
THERMISTOR
MAX1874
USEL
9
REF
BYP
PGND
5
6
7
8
THIN QFN
5mm x 5mm
Functional Diagram appears at the end of the data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.