34675 datasheet(12/24 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34675

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

The 34675 is a fully-integrated Li-Ion and Li-Polymer

battery charger, with a 4.85V/10mA linear regulator in a tiny

package. It uses current, voltage, and temperature control

loops to regulate the charge current. It has up to a 28V input

voltage rating, which makes the handheld device safe even

when connected to a wrong AC adapter. In addition, it

provides a 4.85V/10mA linear regulator.

The 34675 requires only two external capacitors and one

resistor to build a fully functional charger for space-limited

applications such as cell phones, Bluetooth accessories and

MP3 players. Its ultra high accuracy voltage (

±0.7%) and

temperature limited charging current, offer additional battery

safety during charging.

The CC current can be programmed with an external

resistor (RISET). The voltage across this resistor is

proportional to the charge current, so the system can monitor

the charge current during the whole charge cycle. The EOC

threshold is preset to 10% of the CC mode current. For a

deeply discharged battery with a voltage lower than 2.7V, the

34675 charges the battery with a trickle-mode current, which

is 20% of the CC mode current.

The linear regulator provides 4.85V with 10mA capability.

The output is turned on when the input voltage is above the

POR threshold, but lower than the OVP threshold. The Linear

regulator is independent. It is not related to any signals of the

charger, including the enable input pin.

Two indication outputs make it easy to report the input

power status and the charge status to MCUs, or users via

LEDs.

FUNCTIONAL PIN DESCRIPTION

INPUT SUPPLY (VIN)

The supply input. This pin should be bypassed to ground

with a 1.0

μF capacitor.

POWER PRESENT INDICATOR (PPR)

Open-drain logic output to indicate the status of the

supply input voltage. The PPR pin output is singularly

determined by the input voltage.The output is pulled

low if VIN is higher than VPOR. This pin is capable of

sinking at least 9.0mA of current to drive an LED

indicator.

CHARGE INDICATOR (CHG)

Open-drain logic output to indicate the charge status. The

output is low when the 34675 is charging, until the EOC

conditions are reached. This pin is capable of sinking at least

9.0mA of current to drive a LED indicator.

ENABLE (EN)

Active low enable logic Input. This pin is internally pulled to

ground by a weak current source. When left floating, the

charger is enabled. Pulling this pin to a high voltage

externally disables the charger.

GROUND (GND)

Ground.

LINEAR REGULATOR OUTPUT (DET)

The linear regulator output. The output voltage is typically

4.85V. The output current capability is 10mA. Bypass this pin

to ground with a ceramic capacitor between 0.1

μF and 1.0μF.

CC MODE CURRENT SETTING AND CHARGE

CURRENT MONITOR (ISET)

The CC mode current, ICHG, is programmed by connecting

a resistor, RISET, between this pin and ground. When

charging in the CC mode, the voltage at this pin is 1.0V. The

voltage reduces proportionally as the charge current reduces

in the CV mode. During the whole charge cycle, the voltage

at this pin can be used to monitor the charge current, using

the following equation:

where IBAT is the actual charge current, ICHG is the

programmed CC mode current, and VISET is the voltage of the

ISET pin during the whole charge cycle.

CHARGER OUTPUT (BAT)

Charger output pin. Connect this pin to the battery being

charged. Bypass to ground with a 2.2

μF or higher capacitor.

EXPOSED PAD (EPAD)

Exposed pad. This must be soldered to the large ground

plane on the PCB to enhance the thermal conductivity. The

pad must be connected to GND electrically.

BAT

ISET

1.0V

-------------- I

CHG

⋅

34675 Datasheet(PDF) 12 Page - Freescale Semiconductor, Inc

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