LTC4098EPDC-PBF(RevB) 데이터 시트보기 (PDF) - Linear Technology

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LTC4098EPDC-PBF
(Rev.:RevB)

USB Compatible Switching Power Managers/Li-Ion Chargers with Overvoltage Protection

Linear Technology 

LTC4098/LTC4098-1

APPLICATIONS INFORMATION

exceeds 6V plus VF(SCHOTTKY), OVGATE will be pulled to

GND and both the WALL and USB inputs will be protected.

Each input is protected up to the drain-source breakdown,

BVDSS, of MN1 and MN2. R1 must also be rated for the

power dissipated during maximum overvoltage. See the

Operations section for an explanation of this calculation.

Table 4 shows some N-channel MOSFETs that may be

suitable for overvoltage protection.

Table 4. Recommended OVP FETs

N-CHANNEL

MOSFET

Si2302ADS

BVDSS

20V

RON

70mΩ

IRLML2502

20V

35mΩ

Si1472DH

30V

65mΩ

NTLJS4114N

30V

20mΩ

FDN372S

30V

45mΩ

PACKAGE

SOT-23

SOT-23

SC70-6

2mm × 2mm DFN

SOT-23

Reverse Voltage Protection

The LTC4098/LTC4098-1 can also be easily protected

against the application of reverse voltage, as shown in

Figure 8. D1 and R1 are necessary to limit the maximum

VGS seen by MP1 during positive overvoltage events.

D1’s breakdown voltage must be safely below MP1’s

BVGS. The circuit shown in Figure 8 offers forward volt-

age protection up to MN1’s BVDSS and reverse voltage

protection up to MP1’s BVDSS.

USB/WALL

ADAPTER

MP1

MN1

D1

R1

R2

VBUS

C1

LTC4098/

LTC4098-1

OVGATE

OVSENS

VBUS POSITIVE PROTECTION UP TO BVDSS OF MN1

VBUS NEGATIVE PROTECTION UP TO BVDSS OF MP1

40981 F08

Figure 8. Dual-Polarity Voltage Protection

Alternate NTC Thermistors and Biasing

The LTC4098/LTC4098-1 provide temperature-qualified

charging if a grounded thermistor and a bias resistor are

connected to NTC and NTCBIAS. By using a bias resistor

whose value is equal to the room temperature resistance

of the thermistor (R25) the upper and lower temperatures

are preprogrammed to approximately 40°C and 0°C, re-

spectively (assuming a Vishay curve 1 thermistor).

The upper and lower temperature thresholds can be ad-

justed by either a modification of the bias resistor value

or by adding a second adjustment resistor to the circuit.

If only the bias resistor is adjusted, then either the upper

or the lower threshold can be modified but not both. The

other trip point will be determined by the characteristics

of the thermistor. Using the bias resistor in addition to an

40981fb

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