MAX8724ETI+T Maxim Integrated Products, MAX8724ETI+T Datasheet - Page 19

• Manufacturer Part Number: MAX8724ETI+T
• Description: IC CHARGER BATTERY 28-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8724ETI+T

• Function: Charge Management
• Battery Type: Multi-Chemistry
• Voltage - Supply: 8 V ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

V
can drive a p-channel MOSFET directly at the charger
input, providing a lower dropout voltage than a
Schottky diode (Figure 2). In the MAX1908/MAX8724
the ACOK comparator is enabled after REFIN is ready.
In the MAX8765/MAX8765A, the ACOK comparator is
independent of REFIN.
Use ICHG to monitor the battery-charging current being
sensed across CSIP and CSIN. The ICHG voltage is
proportional to the output current by the equation:
where I
the transconductance of ICHG (3µA/mV typ), and R9 is
the resistor connected between ICHG and ground.
Leave ICHG unconnected if not used.
Use IINP to monitor the system input current being
sensed across CSSP and CSSN. The voltage of IINP is
proportional to the input current by the equation:
where I
adapter power, G
(3µA/mV typ), and R10 is the resistor connected between
IINP and ground. ICHG and IINP have a 0 to 3.5V output
voltage range. Leave IINP unconnected if not used.
LDO provides a 5.4V supply derived from DCIN and
can deliver up to 10mA of load current. The MOSFET
drivers are powered by DLOV and BST, which must be
connected to LDO as shown in Figure 1. LDO supplies
the 4.096V reference (REF) and most of the control cir-
cuitry. Bypass LDO with a 1µF capacitor to GND.
The MAX1908/MAX8724/MAX8765/MAX8765A feature
a low-power shutdown mode. Driving SHDN low shuts
down the MAX1908/MAX8724/MAX8765/MAX8765A. In
shutdown, the DC-DC converter is disabled and CCI,
CCS, and CCV are pulled to ground. The IINP and
ACOK outputs continue to function.
SHDN can be driven by a thermistor to allow automatic
shutdown of the MAX1908/MAX8724/MAX8765/
MAX8765A when the battery pack is hot. The shutdown
falling threshold is 23.5% (typ) of V
V
driven by a thermistor.
REF
REFIN
/2. Since ACOK can withstand 30V (max), ACOK
INPUT
CHG
hysteresis to provide smooth shutdown when
V
V
ICHG
IINP
Low-Cost Multichemistry Battery Chargers
is the battery-charging current, G
is the DC current being supplied by the AC
= I
= ICHG x RS2 x G
IINP
______________________________________________________________________________________
INPUT
is the transconductance of IINP
x RS1 x G
Current Measurement
IINP
ICHG
LDO Regulator
x R10
REFIN
x R9
Shutdown
with 1%
ICHG
is
The MAX1908/MAX8724/MAX8765/MAX8765A employ
a buck regulator with a bootstrapped nMOS high-side
switch and a low-side nMOS synchronous rectifier.
The MAX1908/MAX8724/MAX8765/MAX8765A control
input current (CCS control loop), charge current (CCI
control loop), or charge voltage (CCV control loop),
depending on the operating condition.
The three control loops, CCV, CCI, and CCS are brought
together internally at the LVC amplifier (lowest voltage
clamp). The output of the LVC amplifier is the feedback
control signal for the DC-DC controller. The output of the
G
amplifier and also clamps the other two control loops to
within 0.3V above the control point. Clamping the other
two control loops close to the lowest control loop ensures
fast transition with minimal overshoot when switching
between different control loops.
The MAX1908/MAX8724/MAX8765/MAX8765A feature a
variable off-time, cycle-by-cycle current-mode control
scheme. Depending upon the conditions, the MAX1908/
MAX8724/MAX8765/MAX8765A work in continuous or
discontinuous-conduction mode.
With sufficient charger loading, the MAX1908/MAX8724/
MAX8765/MAX8765A operate in continuous-conduction
mode (inductor current never reaches zero) switching at
400kHz if the BATT voltage is within the following range:
The operation of the DC-DC controller is controlled by
the following four comparators as shown in Figure 4:
• IMIN—Compares the control point (LVC) against
• CCMP—Compares the control point (LVC) against the
• IMAX—Compares the charging current (CSI) to 6A
• ZCMP—Compares the charging current (CSI) to
M
333mA (RS2 = 0.015Ω). If ZCMP output is high, then
0.15V (typ). If IMIN output is low, then a new cycle
cannot begin.
charging current (CSI). The high-side MOSFET on-
time is terminated if the CCMP output is high.
(RS2 = 0.015Ω). The high-side MOSFET on-time is
cannot begin until IMAX goes low.
both MOSFETs are turned off.
terminated if the IMAX output is high and a new cycle
3.1V x (number of cells) < V
amplifier that is the lowest sets the output of the LVC
CCV, CCI, CCS, and LVC Control Blocks
Continuous-Conduction Mode
BATT
DC-DC Converter
< (0.88 x V
DC-DC Controller
DCIN
)
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