MAX1874ETE Maxim Integrated Products, MAX1874ETE Datasheet - Page 11

• Manufacturer Part Number: MAX1874ETE
• Description: Battery Management Dual-Input USB/AC Adapter 1-Cell Li+
• Manufacturer: Maxim Integrated Products

Specifications of MAX1874ETE

• Battery Type: Li-Ion, Li-Polymer
• Operating Supply Voltage: 4.35 V to 6.5 V
• Supply Current: 4 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: TQFN-16
• Charge Safety Timers: No
• Mounting Style: SMD/SMT
• Temperature Monitoring: No

acceptable range. To verify that the input voltage is
stable, DCOK has an internal delay of 20ms before con-
necting power to DCLV. DCOK remains operational
when EN is low (charger off).
UOK is an active-low, open-drain output that goes low
to indicate that V
remains operational when EN is low (charger off). An
external 10kΩ pullup resistor keeps UOK high until it is
certain that power is within the acceptable range. UOK
can be used as a logic output, or to control a MOSFET
that switches USB power directly to the system load
when the MAX1874 is powered from a USB source (Q1
in Figure 4).
BYP is the bypass connection for the MAX1874’s inter-
nal power rail. Bypass to GND with a 2.2µF or greater
capacitor. The voltage at BYP is supplied from either
DCLV or USB through an internal 5Ω switch network.
PON goes high when V
operating range. PON can be used as a logic output to
indicate power is connected or can drive an external
P-channel MOSFET that switches the system load from
the battery to an external source when power is applied.
See Q3 in Figures 4 and 5.
When the MAX1874 is powered with a battery connect-
ed, the IC first detects if the cell voltage is ready for full
charge current. If the cell voltage is less than the pre-
qual level (3V typ), the battery is precharged with a
50mA current until the cell reaches the proper level.
The full charging current, as set by USEL or DCI, is
then applied.
The charging current from the USB source is selected
by USEL. A USB source can supply a maximum of
100mA or 500mA. USB hosts and powered hubs typi-
cally supply 500mA, while unpowered hubs supply
Table 2.
Note: CHG does not go high when charge current is reduced by the thermal regulation loop.
DCLV Charging
USB Charging 500mA (USEL high)
USB Charging 100mA (USEL low)
Li+ Charger with OVP and Thermal Regulation
CHARGING SOURCE
CHG Battery Full Indication
USB
______________________________________________________________________________________
is valid (greater than 4V). UOK
DC
USB Power-OK ( UOK )
or V
USB
Dual-Input, USB/AC Adapter, 1-Cell
Charging Current
12.5% of Charge Current Set by DCI and Charger in Voltage Mode
125mA and Charger in Voltage Mode
Charger in Voltage Mode
Power On (PON)
Precharge Current
is within its normal
Bypass (BYP)
CHARGE CURRENT THRESHOLD FOR CHG GOING HIGH
USEL
100mA. A logic low on USEL selects a 100mA maximum
charging current. A logic high on USEL selects a 500mA
maximum charging current.
When charging from the DCLV input, the voltage at DCI
sets the charge current. The voltage-to-current transfer
ratio from DCI to BATT is 1A/V
be connected to a resistive divider from REF to DCI to
GND (R5 and R6 in Figures 2 and 4). In this configura-
tion, I
R5 and R6 should total 25kΩ or more to minimize loading
on REF. Connecting DCI directly to REF results in a 1A
charge current.
CHG is low when the MAX1874 is charging in either the
prequal or full-charging state. CHG then goes high
when the charging current falls below a percentage of
the set fast-charge current (Table 2) and the charger is
in voltage mode (V
threshold is a function of the charger mode. When
charging from a DC source, CHG goes high when
I
charger is in voltage mode (V
charging from a USB source with USEL high, CHG
goes high when I
in voltage mode. If the MAX1874 is charging from a
USB source with USEL low, CHG goes high when the
charger enters voltage mode.
On-chip thermal limiting in the MAX1874 simplifies PCB
layout and allows charging rates to be automatically
optimized without constraints imposed by worst-case
minimum battery voltage, maximum input voltage, and
maximum ambient temperature. When the MAX1874
thermal limit is reached, the charger does not shut
down but simply reduces charging current. This allows
the board design to be optimized for compact size and
typical thermal conditions. The MAX1874 reduces
charging current to keep its die temperature below
+105°C.
BATT
BATT
falls to 12.5% of the current set by V
is as follows:
I
BATT
BATT
= [R6 / (R5 + R6)] Amps
BATT
Package Thermal Limiting
falls to 125mA and the charger is
near 4.2V). The CHG current
REF
BATT
Battery Full ( CHG )
. The DCI pin should
near 4.2V). When
DCI
and the
DCI
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