Rainbow Electronics MAX1874 - Manual (Page 13)

MAX1874
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
______________________________________________________________________________________ 13
MAX1874
USB INPUT
DC INPUT
UP TO 6.0V
C5
4.7 µF
10V CERAMIC
C1
4.7 µF
6.3V CERAMIC
C4
2.2 µF
10V CERAMIC
C3
2.2
µF
6.3V CERAMIC
C6
0.1
µF
10V CERAMIC
TO REF
DCLV
GND
BATT
NTC
THERMISTOR
10k
Ω AT +25°C
PON
REF
THRM
DC
USB
400m Ω
250m Ω Li+
CELL
USEL
500mA
100mA
EN
DCI
PGND BYP
REGULATOR
UOK
CHG
DCOK
R5
100k Ω
R6
301k Ω
R4
10k
Ω
Figure 2. A Minimal Circuit that Assumes System Load Is Only Connected to the Battery. The circuit has a 6.5V maximum input and
disables charging for inputs over 6.2V.
MAX1874
USB INPUT
0VP UP TO 18V
CHARGING UP TO 6.0V
C5
4.7 µF
25V CERAMIC
C1
4.7 µF
6.3V CERAMIC
C4
2.2 µF
10V CERAMIC
C3
2.2
µF
6.3V CERAMIC
C6
0.1
µF
10V CERAMIC
TO REF
DCLV
GND
BATT
NTC
THERMISTOR
10k
Ω AT +25°C
PON
REF
THRM
DC
USB
400m Ω
250m Ω Li+
CELL
USEL
500mA
100mA
EN
DCI
PGND BYP
REGULATOR
UOK
CHG
C2
1 µF
10V CERAMIC
DCOK
R4
10k
Ω
R2
1k Ω
5%
Q2
FDN302
0.055 Ω, -20V
Figure 3. A circuit with overvoltage protection MOSFET (Q2) on DC input withstands up to 18V from the AC adapter and disables
charging at inputs over 6.2V.