MMPF0100 datasheet(103/136 Pages) FREESCALE

103 / 136 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

103

PF0100

Functional Block Requirements and Behaviors

Power Generation

7.4.7.1

Coin Cell Battery Backup

The LICELL pin provides for a connection of a coin cell backup battery or a “super” capacitor. If the voltage at VIN goes below

the VIN threshold (VTL1 and VTL0), contact-bounced, or removed, the coin cell maintained logic will be powered by the voltage

applied to LICELL. A small capacitor should be placed from LICELL to ground under all circumstances.

Coin Cell Charger Control

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 charger is enabled via the COINCHEN bit while the coin cell voltage is

programmable through the VCOIN[2:0] bits on register COINCTL on Table 112. The coin cell charger voltage is programmable.

In the ON state, the charger current is fixed at ICOINHI. In Sleep and Standby modes, the charger current is fixed at ICOINLO

as indicated in Table 114 .In the OFF state, coin cell charging is not available as the main battery could be depleted

unnecessarily. The coin cell charging will be stopped when VIN is below UVDET.

External Components

Table 111. Coin Cell Charger Voltage

VCOIN[2:0]

VCOIN (V)(66)

000

2.50

001

2.70

010

2.80

011

2.90

100

3.00

101

3.10

110

3.20

111

3.30

Notes

66.

Coin cell voltages selected based on the

type of LICELL used on the system.

Table 112. Register COINCTL - ADDR 0x1A

Name

Bit #

R/W

Default

Description

VCOIN

2:0

R/W

0x00

Coin cell charger output voltage selection.

See Table 111 for all options selectable through

these bits.

COINCHEN

R/W

0x00

Enable or disable the Coin cell charger

UNUSED

7:4

–

0x00

UNUSED

Table 113. Coin Cell Charger External Components

Component

Value

Units

LICELL Bypass Capacitor

100

LICELL Bypass Capacitor as coin cell replacement

4.7

μF

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