UCS2112 datasheet(24/64 Pages) MICROCHIP

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UCS2112

DS20005424B-page 24

 2015 Microchip Technology Inc.

5.4

Discrete Output Pins

5.4.1

ALERT#1 AND ALERT#2 OUTPUT

PINS

The UCS2112 has two independent ALERT# out pins.

ALERT#1 is tied to the status of the VBUS1 pin.

ALERT#2 is tied to the status of the VBUS2 pin.

The ALERT# pin is an active-low open-drain interrupt

to the host controller. The ALERT# pin is asserted

when an error occurs. The ALERT# pin can also be

asserted when the LOW_CUR (portable device is pull-

ing less current and may be finished charging) or

TREG (thermal regulation temperature exceeded) bits

are set and linked. As well, when charge rationing is

enabled, the ALERT# pin is asserted by default when

the current rationing threshold is reached (as deter-

mined by RATION_BEH<1:0>). The ALERT# pin is

released when all error conditions that may assert the

ALERT# pin (such as an error condition, charge

rationing, and TREG and LOW_CUR if linked) have

been removed or reset as necessary.

5.4.2

BOOST# OUTPUT PIN

The UCS2112 provides a BOOST# output pin to com-

pensate for voltage drops during high loads. The

BOOST# pin is an active-low, open-drain output that

would be connected to a resistor in the DC-DC Con-

verter’s feedback error voltage loop (see Figure 5-3).

The

BOOST#

asserted

when

VBUS Current > IBOOST. IBOOST typical value is 1.9A.

The BOOST# is OR’ed for both VBUS1 and VBUS2 ports.

When the BOOST# pin is asserted, it will remain in this

state for at least tBOOST_MAT (minimum assertion time).

FIGURE 5-3:

Boost# Pin Usage.

5.5

Discrete Input Pins

5.5.1

COMM_ILIM INPUT

The COMM_ILIM input determines the communica-

tions mode, as shown in Table 7-1. This is also the

hardware strap for MAX Current Limit.

5.5.2

SMCLK

When operated in Stand-Alone mode, this pin should be

tied to ground. When the UCS2112 is configured for

SMBus communications, the SMCLK is the clock input.

5.5.3

SMDATA

When used in Stand-Alone, this pin should be tied to

ground.

When the UCS2112 is configured for SMBus commu-

nications, the SMDATA is the data input/output.

DC-DC

Converter Block

5.0VOUT

FeedBack

GND

VFB

A_DET#1

PWR_EN1

BOOST#

PWR_EN2

A_DET#2

VBUS1

COMM_ILIM

GND FLAG

UCS2112

20-QFN 4x4 mm

VBUS1

VBUS2

OUT

 V



--------------------------------------------------------

OUT



 R



--------------------------------------------------------

OUT



OUT

--------------------

------

–





 R1 VFB



------------------------



If R1 R3



OUT



OUT



---------------------------------



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