Rainbow Electronics MAX1874 - Manual (Page 8)

MAX1874
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
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Pin Description
PIN NAME FUNCTION
1 DCLV
Low-Voltage Charger Input. DCLV charges BATT through an internal MOSFET. Maximum operating
voltage at this pin is 6.0V. When an overvoltage protection MOSFET is connected, DCLV is connected to
DC when the input voltage is suitable for charging.
2 DC Voltage-Sense Pin for DC Input from AC Adapter. Maximum operating voltage at this pin is 18V.
3 CHG
CHG is an active-low, open-drain output that goes low when the MAX1874 is charging and goes high
when both of the following conditions are met (see the Battery Full (
CHG ) section):
1) Charge current drops to a set threshold (Table 2).
2) The charger is in voltage mode.
4 USEL
USEL is a logic input that sets USB source charging current to 500mA when USEL is logic high and to
100mA when USEL is logic low.
5 EN
Enable/Disable Input. Drive EN high to enable the device. When EN is low, UOK, DCOK, PON, and REF
remain active.
6 GND Ground
7 DCI
The voltage at this input sets the fast-charge current when the DCLV input is powering the charger. See
the Charging Current section.
8 THRM
THRM pauses charging when an externally connected thermistor (10k Ω at +25°C) is at less than 0°C or
greater than +50 °C. Connect to GND to disable. See the External Thermistor Monitor (THRM) section.
9 REF
3V Reference Output. Sources up to 500µA to bias I DCI and external thermistor. Bypass with 0.1µF to
GND. REF loading does not affect BATT regulation accuracy.
10 PGND Power Ground. Connect to GND at a single, low-impedance point.
11 BYP
BYP powers internal circuitry and switches to the active input (either DCLV or USB). Bypass with a 2.2µF
capacitor to GND.
12 USB USB Charger Input. Charges BATT through an internal MOSFET.
13 UOK
UOK is an active-low, open-drain output that goes low to indicate when the USB input is the valid
charging source.
14 PON
PON is an active-high, open-drain output with an internal 120k Ω resistor to ground that goes high when
V DC or V USB > V BATT . PON can directly drive an external PFET that disconnects the battery from the
system load when power is applied.
15 BATT Charge Output. Connect to the positive terminal of the Li+ battery.
16 DCOK DCOK is an active-low, open-drain output that goes low when 3.5V < V
DC < 6.2V.