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LTC4160/LTC4160-1

41601f

APPLICATIONS INFORMATION

There are MLCCs available with several types of dielectrics

each having considerably different characteristics. For

example, X7R MLCCs have the best voltage and tempera-

ture stability. X5R MLCCs have apparently higher packing

density but poorer performance over their rated voltage

and temperature ranges. Y5V MLCCs have the highest

packing density, but must be used with caution, because

of their extreme nonlinear characteristic of capacitance

versus voltage. The actual in-circuit capacitance of a

ceramic capacitor should be measured with a small AC

signal and DC bias as is expected in-circuit. Many vendors

specify the capacitance versus voltage with a 1VRMS AC

test signal and, as a result, over state the capacitance that

the capacitor will present in the application. Using similar

operating conditions as the application, the user must

measure or request from the vendor the actual capacitance

to determine if the selected capacitor meets the minimum

capacitance that the application requires.

Overvoltage Protection

VBUS can be protected from overvoltage damage with two

additional components, a resistor R1 and an N-channel

MOSFET MN1, as shown in Figure 5. Suitable choices for

MN1 are listed in Table 4.

Table 4. Recommended N-Channel MOSFETs for the Overvoltage

Protection Circuit

PART #

BVDSS

RON

PACKAGE

Si1472DH

30V

57mΩ

SC70-6

Si2302ADS

20V

60mΩ

SOT-23

Si2306BDS

30V

47mΩ

SOT-23

Si2316DS

30V

50mΩ

SOT-23

IRLML2502

20V

50mΩ

SOT-23

FDN372S

30V

50mΩ

SOT-23

NTLJS4114N

30V

35mΩ

WDFN6

R1 is a 6.2k resistor and must be rated for the power dis-

sipated during maximum overvoltage. In an overvoltage

condition the OVSENS pin will be clamped at 6V. R1 must

be sized appropriately to dissipate the resultant power.

For example, a 1/10W 6.2k resistor can have at most

√(PMAX • 6.2kΩ) = 25V applied across its terminals. With

the 6V at OVSENS, the maximum overvoltage magnitude

that this resistor can withstand is 31V. A 1/4W 6.2k resis-

tor raises this value to 45V. OVSENS’s absolute maximum

current rating of 10mA imposes an upper limit of 68V

protection.

Reverse Voltage Protection

The LTC4160/LTC4160-1 can also be easily protected

against the application of reverse voltages, as shown in

Figure 6. 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 6 offers forward voltage protection

up to MN1’s BVDSS and reverse voltage protection up to

MP1’s BVDSS.

Figure 5. Overvoltage Protection

Figure 6. Dual Polarity Voltage Protection

USB/WALL

ADAPTER

41601 F05

MN1

VBUS

OVSENS

OVGATE

LTC4160/

LTC4160-1

Battery Charger Over Programming

The USB high power speciﬁcation allows for up to 2.5W

to be drawn from the USB port. The LTC4160/LTC4160-1’s

bidirectional switching regulator in step-down mode con-

verts the voltage at VBUS to a voltage just above BAT on

VOUT, while limiting power to less than the amount pro-

grammed at CLPROG. The charger should be programmed

(with the PROG pin) to deliver the maximum safe charging

current without regard to the USB speciﬁcations. If there

is insufﬁcient current available to charge the battery at the

programmed rate, the charge current will be reduced until

the system load on VOUT is satisﬁed and the VBUS cur-

rent limit is satisﬁed. Programming the charger for more

USB/WALL

ADAPTER

41601 F06

MN1

MP1

VBUS POSITIVE PROTECTION UP TO BVDSS OF MN1

VBUS NEGATIVE PROTECTION UP TO BVDSS OF MP1

VBUS

OVSENS

OVGATE

LTC4160/

LTC4160-1

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