LTC4098EUDC-3.6 查看數據表（PDF） - Linear Technology

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LTC4098EUDC-3.6

USB Compatible Switching Power Manager/LiFePO4 Charger with Overvoltage Protection

Linear Technology 

LTC4098-3.6

PIN FUNCTIONS

OVSENS (Pin 1): Overvoltage Protection Sense Input.

OVSENS should be connected through a 6.04k resistor

to the input power connector and the drain of an external

N-channel MOSFET pass transistor. When the voltage on

this pin exceeds a preset level, the OVGATE pin will be

pulled to GND to disable the pass transistor and protect

downstream circuitry. If overvoltage protection is not

desired, connect OVSENS to GND.

OVGATE (Pin 2): Overvoltage Protection Gate Output.

Connect OVGATE to the gate pin of an external N-chan-

nel MOSFET pass transistor. The source of the transistor

should be connected to VBUS and the drain should be

connected to the product’s DC input connector. This pin is

connected to an internal charge pump capable of creating

sufficient overdrive to fully enhance the pass transistor. If

an overvoltage condition is detected, OVGATE is brought

rapidly to GND to prevent damage to downstream circuitry.

OVGATE works in conjunction with OVSENS to provide

this protection. If overvoltage protection is not desired,

leave OVGATE open.

CLPROG (Pin 3): USB Current Limit Program and Monitor

Pin. A 1% resistor from CLPROG to ground determines

the upper limit of the current drawn from the VBUS pin.

A precise fraction of the input current, hCLPROG, is sent

to the CLPROG pin when the high side switch is on. The

switching regulator delivers power until the CLPROG

pin reaches 1.188V. Therefore, the current drawn from

VBUS will be limited to an amount given by hCLPROG and

RCLPROG. There are several ratios for hCLPROG available,

two of which correspond to the 500mA and 100mA USB

specifications. A multilayer ceramic averaging capacitor

is also required at CLPROG for filtering.

NTCBIAS (Pin 4): NTC Thermistor Bias Output. If NTC

operation is desired, connect a bias resistor between

NTCBIAS and NTC, and an NTC thermistor between NTC

and GND. To disable NTC operation, connect NTC to GND

and leave NTCBIAS open.

NTC (Pin 5): Input to the NTC Thermistor Monitoring

Circuits. The NTC pin connects to a negative temperature

coefficient thermistor which is typically co-packaged with

the battery pack to determine if the battery is too hot or too

cold to charge. If the battery’s temperature is out of range,

charging is paused until the battery temperature re-enters

the valid range. A low drift bias resistor is required from

NTCBIAS to NTC and a thermistor is required from NTC

to ground. If the NTC function is not desired, the NTC pin

should be grounded.

BATSENS (Pin 6): Battery Voltage Sense Input. For proper

operation, this pin must always be connected to BAT. For

best performance, connect BATSENS to BAT physically

close to the LiFePO4 cell.

PROG (Pin 7): Charge Current Program and Charge Cur-

rent Monitor Pin. Connecting a 1% resistor from PROG

to ground programs the charge current. If sufficient input

power is available in constant-current mode, this pin servos

to 1V. The voltage on this pin always represents the actual

charge current by using the following formula:

IBAT

=

VPROG

RPROG

• 1030

CHRG (Pin 8): Open-Drain Charge Status Output. The

CHRG pin indicates the status of the battery charger. Four

possible states are represented by CHRG: charging, not

charging, unresponsive battery and battery temperature

out of range. CHRG is modulated at 35kHz and switches

between a low and a high duty cycle for easy recognition

by either humans or microprocessors. CHRG requires a

pull-up resistor and/or LED to provide indication.

GND (Pin 9, Exposed Pad Pin 21): The exposed pad and

pin must be soldered to the PCB to provide a low electrical

and thermal impedance connection to ground.

IDGATE (Pin 10): Ideal Diode Amplifier Output. This pin

controls the gate of an external P-channel MOSFET transis-

tor used to supplement the internal ideal diode. The source

of the P-channel MOSFET should be connected to VOUT

and the drain should be connected to BAT.

BAT (Pin 11): Single-Cell LiFePO4 Battery Pin. Depending

on available power and load, a LiFePO4 battery on BAT will

either deliver system power to VOUT through the ideal diode

or be charged from the battery charger. The LTC4098-3.6

will charge to a float voltage of 3.600V.

VOUT (Pin 12): Output Voltage of the Switching PowerPath

Controller and Input Voltage of the Battery Charger. The

409836f

9

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