RT9728CHGE datasheet(9/13 Pages) RICHTEK

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RT9728C

DS9728C-00 October 2015

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Applications Information

The RT9728C is a single P-MOSFET high-side power

switch with active-high/low enable input, optimized for self-

powered and bus-powered Universal Serial Bus (USB)

applications. The switch's low RDS(ON) meets USB voltage

drop requirements and a flag output is available to indicate

fault conditions to the local USB controller.

Current Limiting and Short Circuit Protection

When a heavy load or short circuit situation occurs while

the switch is enabled, large transient current may flow

through the device. The RT9728C includes a current-limit

circuitry to prevent these large currents from damaging

the MOSFET switch and the hub downstream ports. The

RT9728C provides an adjustable current limit threshold

between 120mA and 1.3A (typ) via an external resistor,

RILIM, between 19.1k

Ω and 232kΩ. However, if the ILIM

pin is connected to VIN, the current limit threshold will be

75mA (typ). Once the current limit threshold is exceeded,

Figure 1. Current Limit Threshold vs RILIM

Current Limit Threshold vs. RILIM

200

400

600

800

1000

1200

1400

1600

110

140

170

200

230

RILIM (k )

the device enters constant-current mode until either

thermal shutdown occurs or the fault is removed. The

table1 shows a recommended current limit value vs. RILIM

resistor.

Table 1. Recommended RILIM Resistor Selections

Desired Nominal

Current Limit

(mA)

Ideal Resistor

)

Closet 1%

Resistor (k

)

Actual Limits (Include R Tolerance)

IOS Min (mA)

IOS Nom (mA)

IOS Max (mA)

Short ILIM to VIN

50.0

75.0

100.0

120

226.1

226.0

101.3

120.0

142.1

200

134.0

133.0

173.7

201.5

233.9

300

88.5

88.7

262.1

299.4

342.3

400

65.9

66.5

351.1

396.7

448.7

500

52.5

52.3

443.9

501.6

562.4

600

43.5

43.2

535.1

604.6

674.1

700

37.2

37.4

616.0

696.0

776.0

800

32.4

708.7

800.8

892.9

900

28.7

797.8

901.5

1005.2

1000

25.8

26.1

875.4

989.1

1102.8

1100

23.4

23.2

982.1

1109.7

1237.3

1200

21.4

21.5

1057.9

1195.4

1332.9

1300

19.7

19.6

1178.0

1308.5

1439.0

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