UCS1001 datasheet(35/59 Pages) MICROCHIP

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USB Port Power Controller with Charger Emulation

Datasheet

SMSC UCS1001

Revision 1.2 (05-21-12)

DATASHEET

Chapter 6 USB Port Power Switch

6.1

USB Port Power Switch

To assure compliance to various charging specifications, the UCS1001 contains a USB port power

switch that supports two current limiting modes: trip and constant current (variable slope). The current

limit (ILIM) is pin selectable. The switch also includes soft start circuitry and a separate short circuit

current limit.

The port power switch is on in the Active state (except when VBUS is discharging).

6.2

Current Limiting

6.2.1

Current Limit Setting

The UCS1001 hardware set current limit, ILIM, can be one of eight values (see Table 6.1). This resistor

value is read once upon UCS1001 power-up. Unless connected to VDD, the resistors in Table 6.1 are

pull-down resistors.

APPLICATION NOTE: If it is necessary to connect the ILIM pin to VDD via a pull-up resistor, it is recommended

that this resistor value not exceed 100 k

.

APPLICATION NOTE: ILIM pin pull-down resistors with values less than 33 k

 will cause unexpected behavior.

6.2.2

Short Circuit Output Current Limiting

Short circuit current limiting occurs when the output current is above the selectable current limit (ILIMx).

This event will be detected and the current will immediately be limited (within tSHORT_LIM time). If the

condition remains, the port power switch will flag an Error condition and enter the Error state (see

Section 4.1.5, "Error State Operation").

Table 6.1 UCS1001 ILIM Selection

ILIM RESISTOR (±5%)

ILIM SETTING

47 k



500 mA

56 k



900 mA

68 k



1000 mA

82 k



1200 mA

100 k



1500 mA

120 k



1800 mA

150 k



2000 mA

VDD

2500 mA

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