LTC4120 datasheet(8/24 Pages) AD

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LTC4126-ADJ

Rev. 0

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CHRG (Pin 6): Open-Drain Charge Status Output Pin. This

pin can be pulled up through a resistor and/or an LED to

indicate the status of the battery charger. This pin has

four possible states: slow blink to indicate charging, fast

blink to indicate a fault, pulled down to indicate charging

done, and high impedance to indicate no input power. To

conserve power, the pull-down current is limited to 300µA.

ACIN (Pin 7): AC Input Voltage Pin. Connect the external

LC tank, which includes the receive coil, to this pin. Con-

nect this pin to GND when not used.

BAT (Pin 8): Battery Connection Pin. Connect a single-cell

Li-Ion battery to this pin. Whenever enough input power

(AC or DC) is available, the battery will be charged via this

pin. Additionally, the DC/DC Converter is powered from

the battery via this pin. To minimize the effect of switching

noise from the DC/DC converter on charger performance,

this pin should be decoupled with a 1µF capacitor to GND

if the DC/DC converter is enabled while charging.

STAT2 (Pin 9), STAT1 (Pin 10): Digital CMOS Logic Status

Output Pins. The low level of these pins is referenced to

GNDandthehighlevelisreferencedtoVOUT.Consequently,

PIN FUNCTIONS

these indicators are not available if the DC/DC is disabled.

These two pins together with ACPR indicate the various

charging states and fault conditions. However, when no

inputpowerisavailableandtheDC/DCconverterisenabled,

these pins instead indicate the voltage level of the battery.

VCC (Pin 11): DC Input Voltage Pin. An internal diode is

connected from the ACIN pin (anode) to this pin (cathode).

When an AC voltage is present at the ACIN pin, the voltage

on this pin is the rectified AC voltage. When the ACIN pin

is not used (or shorted to GND), connect this pin to a DC

voltage source to provide power to the LTC4126-ADJ and

charge the battery.

OUT (Pin 12): DC/DC Converter Output Pin. This pin pro-

vides 1.2V to power hearing aid ASICs. A low ESR ceramic

capacitor of at least 2.2μF should be placed close to this

pin to stabilize the converter.

GND (Exposed Pad Pin 13): Ground Pin. The exposed pad

on the backside of the package must be soldered to the

PCB ground for a low-resistance electrical connection as

well as for optimum thermal performance.

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