13892 datasheet(49/75 Pages) FREESCALE

49 / 75 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

13892

FUNCTIONAL DEVICE OPERATION

Because of an order from the United States International Trade Commission, BGA-packaged product lines and part numbers indicated here currently are not

available from Freescale for import or sale in the United States prior to September 2010: MC13892VK and MC13892VL in 139, 186 MAPBGA packages.

COIN CELL BATTERY BACKUP

The LICELL pin provides a connection for a coin cell

backup battery or supercap. If the main battery is deeply

discharged, removed, or contact-bounced (i.e., during a

power cut), the RTC system and coin cell maintained logic

will switch over to the LICELL for backup power. A small

capacitor should be placed from LICELL to ground under all

circumstances.

Coin cells can get damaged and their lifetime reduced

when deeply discharged. In order to avoid this, the internal

circuitry supplied from LICELL is disconnected for voltages

below the coin cell disconnect threshold. This will also cause

the ADC reading of the coin cell voltage to yield zero.

The coin cell charger circuit will function as a current-

limited voltage source, resulting in the CC/CV taper

characteristic typically used for rechargeable Lithium-Ion

batteries. The coin cell voltage is programmable from 2.5 to

3.3 V in 0.1 V steps, excepting 2.6 V. The coin cell charger

voltage is programmable in the ON state where the charge

current is fixed at ICOINHI. When the device is working in any

of the low Power Off modes, the coin cell charger will also go

into a low power mode in which the current it supplies to the

coin cell will be reduced in order to save power.

CONTROL INTERFACE SPI/I2C

The IC contains a number of programmable registers for

control and communication. The majority of registers are

accessed through an SPI interface in a typical application.

The same register set may be alternatively accessed with an

I2C interface that is muxed on SPI pins. The following table

describes the muxed pin options for the SPI and I2C

interfaces.

Table 12. 13892 Coin Cell Battery Electrical Characteristics

PARAMETER

TYP

UNITS

Voltage Accuracy

100

Coin Cell Charge Current in On and Watchdog modes ICOINHI

µA

Coin Cell Charge Current in Off and Low Power Off modes (User Off/Memory Hold) ICOINLO

µA

Current Accuracy

LICELL Bypass Capacitor

100

LICELL Bypass Capacitor as coin cell

4.7

µF

Table 13. 13892 Muxed Pin Options for SPI and I2C Interfaces (SPI Functions)

PIN NAME

SPI MODE FUNCTIONALITY

Configuration (52)

Chip Select

CLK

SPI Clock

MISO

Master In, Slave Out (data input)

MOSI

Master Out, Slave In (data input)

Notes

52.

CS held low at Cold Start configures the interface for SPI mode; once activated,

CS functions as the SPI Chip Select.

13892 Datasheet(PDF) 49 Page - Freescale Semiconductor, Inc

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