LTC4156IUFD View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC4156IUFD

Dual-Input Power Manager/3.5A LiFePO4 Battery Charger with I2C Control and USB OTG

Linear Technology 

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LTC4156

PIN FUNCTIONS

SDA (Pin 1): Data Input/Output for the I2C Serial Port.

The I2C input levels are scaled with respect to DVCC for

I2C compliance.

DVCC (Pin 2): Logic Supply for the I2C Serial Port. DVCC

sets the reference level of the SDA and SCL pins for I2C

compliance. It should be connected to the same power

supply used to power the I2C pull-up resistors.

IRQ (Pin 3): Open-Drain Interrupt Output. The IRQ pin

can be used to generate an interrupt due to a variety of

maskable status change events within the LTC4156.

ID (Pin 4): USB A-Device Detection Pin. When wired to a

mini- or micro-USB connector, the ID pin detects when

the “A” side of a mini or micro-USB cable is connected

to the product. If the ID pin is pulled down, and the

LOCKOUT_ID_PIN bit is not set in the I2C port, the switch-

ing PowerPath operates in reverse providing USB power

to the VBUS pin from the battery. USB On-The-Go power

can only be delivered from the USB multiplexer path.

CLPROG1 (Pin 5): Primary VBUS Current Limit Program-

ming Pin. A resistor from CLPROG1 to ground determines

the upper limit of the current drawn from the VBUS pin when

CLPROG1 is selected. A precise measure of VBUS current,

hCLPROG1–1, is sent to the CLPROG1 pin. The switching

regulator increases power delivery until CLPROG1 reaches

1.2V. Therefore, the current drawn from VBUS will be

limited to an amount given by the 1.2V reference voltage,

hCLPROG1 and RCLPROG1.

Typically CLPROG1 is used to override the USB compliant

input current control pin, CLPROG2, in applications where

USB compliance is not a requirement. This would be use-

ful for applications that use a dedicated wall adapter and

would rather not be limited to the 500mW start-up value

required by USB specifications. If USB compliance is a

requirement at start-up, CLPROG1 should be connected

to CLPROG2 and a single resistor should be used. See

the CLPROG2 pin description.

In USB noncompliant designs, the user is encouraged to

use an RCLPROG1 value that best suits their application

for start-up current limit. See the Operation section for

more details.

CLPROG2 (Pin 6): Secondary VBUS Current Limit Pro-

gram Pin. CLPROG2 controls the VBUS current limit when

either selected via I2C command or when CLPROG1 and

CLPROG2 are shorted together. When selected, a resistor

from CLPROG2 to ground determines the upper limit of

the current drawn from the VBUS pin. Like CLPROG1, a

precise fraction of VBUS current, hCLPROG2–1, is sent to the

CLPROG2 pin. The switching regulator increases power

delivery until CLPROG2 reaches 1.2V. Therefore, the cur-

rent drawn from VBUS will be limited to an amount given

by the 1.2V reference voltage, hCLPROG2 and RCLPROG2.

There are a multitude of ratios for hCLPROG2 available by I2C

control, three of which correspond to the 100mA, 500mA

and 900mA USB specifications. CLPROG2 is also used to

regulate maximum input current in the USB suspend mode

and maximum output current in USB On-The-Go mode.

If CLPROG1 and CLPROG2 are shorted together at the onset

of available input power, the LTC4156 selects CLPROG2 in

the 100mA USB mode to limit input current. This ensures

USB compliance if so desired. For USB compliance in all

modes, the user is encouraged to make RCLPROG2 equal

to the value declared in the Electrical Characteristics.

WALLSNS (Pin 7): Highest Priority Multiplexer Input and

Overvoltage Protection Sense Input. WALLSNS should be

connected through a 3.6k resistor to a high priority input

power connector and one drain of two source-connected

N-channel MOSFET pass transistors. When voltage is

detected on WALLSNS, it draws a small amount of current

to power a charge pump which then provides gate drive to

WALLGT to energize the external transistors. If the input

voltage exceeds VOVLO, WALLGT will be pulled to GND

to disable the pass transistors and protect the LTC4156

from high voltage.

USBSNS (Pin 8): Lowest Priority Multiplexer Input and

Overvoltage Protection Sense Input. USBSNS should be

connected through a 3.6k resistor to a low priority input

power connector and one drain of two source-connected

N-channel MOSFET pass transistors. When voltage is

detected on USBSNS, and no voltage is detected on

WALLSNS, USBSNS draws a small amount of current to

power a charge pump which then provides gate drive to

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