UCS2113 datasheet(22/62 Pages) MICROCHIP

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UCS2113

DS20005680B-page 22

 2016-2021 Microchip Technology Inc. and its subsidiaries

6.0

USB PORT POWER SWITCH

assure

compliance

various

charging

specifications, the UCS2113 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 (and may be updated via

the register set). 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).

6.1

Current Limiting

6.1.1

CURRENT LIMIT SETTING

The UCS2113 hardware set current limit, ILIM, can be

one of eight values. This resistor value is read once

upon UCS2113 power-up. The current limit can be

changed via the SMBus/I2C after power-up; however,

the programmed current limit cannot exceed the hard-

ware set current limit. Unless connected to VDD, the

resistors in Table 6-1 are pull-down resistors.

At power-up, the communication mode (Stand-Alone

or SMBus/I2C) and hardware current limit (ILIM) are

determined via the pull-down resistor (or pull-up

resistor if connected to VDD) on the COMM_ILIM pin,

as shown in Table 6-1.

6.1.2

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.

6.1.3

SOFT START

When the PWR_EN control changes states to enable the

port power switch, the UCS2113 invokes a soft start

routine for the duration of the VBUS rise time (tR_BUS).

This soft start routine will limit current flow from VS into

VBUS while it is active. This circuitry will prevent current

spikes due to a step in the portable device current draw.

In the case when a portable device is attached while the

PWR_EN pin is already enabled, if the bus current

exceeds ILIM, the UCS2113 current limiter will respond

within a specified time (tSHORT_LIM) and will operate

normally at this point. The CBUS capacitor will deliver the

extra current, if any, as required by the load change.

6.1.4

CURRENT LIMITING MODES

The UCS2113 current limiting has two modes: Trip and

Constant Current (variable slope). Either mode

functions at all times when the port power switch is

closed.

6.1.4.1

Trip Mode

When using Trip current limiting, the UCS2113 USB

port power switch functions as a low-resistance switch

and rapidly turns off if the current limit is exceeded.

While operating using Trip current limiting, the VBUS

output voltage will be held relatively constant (equal to

the VS voltage minus the RON xIBUS current) for all

current values up to the ILIM.

If the current drawn by a portable device exceeds ILIM,

the following occurs:

The port power switch will be turned off (Trip

action).

The UCS2113 will enter the Error state and

assert the ALERT# pin.

The fault handling circuitry will then determine

subsequent actions.

TABLE 6-1:

ILIM DECODE

COMM_ILIM

Pulldown

Resistor

(±1%)

PWR_EN1

and

PWR_EN2

Polarity

ILIM (A)

Total ILIM

(A)

(Note 1)

GND

Active-High

0.53

0.53+0.53

10 kΩ

Active-High

0.96

0.96+0.96

12 kΩ

Active-High

1.07

1.07+1.07

15 kΩ

Active-High

1.28

1.28+1.28

18 kΩ

Active-High

1.6

1.6+1.6

22 kΩ

Active-High

2.13

2.13+2.13

27 kΩ

Active-High

2.67

2.67+2.67

33 kΩ

Active-High

3.2

3.2+3.2

47 kΩ

Active-Low

0.53

0.53+0.53

56 kΩ

Active-Low

0.96

0.96+0.96

68 kΩ

Active-Low

1.07

1.07+1.07

82 kΩ

Active-Low

1.28

1.28+1.28

100 kΩ

Active-Low

1.6

1.6+1.6

120 kΩ

Active-Low

2.13

2.13+2.13

150 kΩ

Active-Low

2.67

2.67+2.67

VDD

Active-Low

3.2

3.2+3.2

Note 1: The total maximum current depends on

power dissipation characteristics of the

design (see Table 1-1).

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