UCS3205 datasheet(14/30 Pages) MICROCHIP

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UCS3205

DS20006433A-page 14

 2020 Microchip Technology Inc.

4.0

FUNCTIONAL DESCRIPTION

The UCS3205 is a single-channel load switch with highly

integrated load protection for applications up to 22V.

The device protects the power supply with its configurable

current limit feature. The current limit threshold is set with

an external resistor. The same pin can be connected to

external measurement or detection circuitry, such as an

ADC, comparator or MCU, eliminating the need for a

shunt in the power path.

The UCS3205 protects the load from being supplied by

voltages higher than intended (overvoltage lockout). It

also has a thermal shutdown circuit, which will shut the

switch off when junction temperature exceeds the limit.

The device implements Fast Role Swap (FRS) capability

and reverse current blocking that can be disabled via the

DIR pin, allowing it to work as a bidirectional switch

depending on the application requirements. The

device’s DIR pin is normally grounded for Fast Role

Swap applications. The FRS pin is normally

grounded for bidirectional current flow applications.

This device can be programmed to either latch off or

retry in the event of a Fault.

4.1

Mode Control

Figure 4-1 shows the UCS3205 state diagram.

4.1.1

RESET MODE

When the UCS3205 is in the Reset state, the device is

in its lowest current consumption state. The port power

switch is off. The FAULT# pin is not asserted. If the

FAULT# pin is asserted prior to entering Reset state, it

will be released. When in Reset mode, a low-to-high

transition on the EN pin will start the transition of the

UCS3205 to its next state. If there are no Faults

detected and t > t STRT_CLD has elapsed, the UCS3205

will transition into the Operating state. If there is an

Overvoltage, Back-Voltage, Short-Circuit, Overcurrent,

or Thermal Shutdown Fault, the device will transition

into the Fault state.

4.1.2

OPERATING MODE

In order for the UCS3205 to enter Operating mode,

VIN/VOUT must be above VIN_STRT/VOUT_STRT for

tSTRT_EN, before the low-to-high transition on EN,

before turning on the switch can take place. Once the

switch is on, the VIN voltage can be decreased to

2.85V. Whenever the UCS3205 is in Operating mode,

the port power switch will be on. In this case, the

FAULT# pin is not asserted. If the FAULT# pin is

asserted prior to entering Reset state, it will be

released. The UCS3205 cannot be in the Operating

state if any of the following conditions exist:

• Overvoltage, Short-Circuit, Overcurrent, Thermal

Shutdown or Back-Voltage Fault

•VIN < VUV_HIGH

•EN < VIH

When in Operating mode, a high-to-low transition on

the EN pin will make the UCS3205 transition into the

Reset state. If any Fault conditions occur while in the

Operating state, the UCS3205 will automatically

transition into the Fault state.

4.1.3

FAULT MODE

The UCS3205 automatically enters the Fault state from

the Operating and Retry states when any of the

following events are detected:

• An Overvoltage (OV) condition on the VIN pin

(see Section 4.4 “VIN Overvoltage Detection”).

• A Short-Circuit (SC) condition (see Section 4.3

“Short-Circuit Detection”).

• An Overcurrent (OC) condition (see Section 4.2

“Overcurrent Detection”).

• Maximum allowable internal die temperature is

exceeded – Thermal Shutdown (TSD) (see

Section 4.8 “Thermal Shutdown”).

• A Back-Voltage (BV) condition (see Section 4.7

“Back-Voltage Detection”).

The UCS3205 enters the Fault state from the Reset

state when there is a low-to-high transition on the EN

pin and any of the following events are detected:

• Maximum allowable internal die temperature is

exceeded

• Back-Voltage condition,

• Short-Circuit condition on the VOUT pin

• Overcurrent condition on the VOUT pin

• Overvoltage condition on the VIN pin

When the UCS3205 is in Fault mode, the port power

switch will be off and the FAULT# pin is asserted.

4.1.4

RETRY MODE

The only way for the UCS3205 to enter the Retry state

is from the Fault state and the LATCH pin must be low.

When the UCS3205 is in Retry mode, the port power

switch will be on and the FAULT# pin is asserted (see

Figure 4-5).

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