LN2053

Rev.1.1 —Aug. 20, 2015

9

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TEMP pin voltage is within the battery NTC thermistor and a resistor divider network, and illustrated in Figure 2.

LN2053 the TEMP pin voltage with the chip and the two thresholds VLOW VHIGH compared to confirm whether the battery

temperature exceeds the normal range. In the LN2053, VLOW were fixed in 30% × VIN, VHIGH were fixed in 60% × VIN. If the

TEMP pin voltage VTEMP <VLOW or VTEMP> VHIGH, the battery temperature is too high or too low, charging will be

suspended; If the TEMP pin voltage VTEMP VLOW and VHIGH in between, the charge cycle will continue.

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Enable design

By controlling whether the ISET pin resistor connected, users can reach close LN2053 function. Figure 4:

Figure4. LN2053 Enable Design

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Open-drain output status indication

LN2053has two open-drain status indication sides, CHAG and DONE, the two status indicator LEDs client can drive or

microcontroller port. CHAG used to indicate charging status, charging time, CHAG is low; DONE to indicate the charging end of

the state, when the charging end, DONE is low. When the battery temperature is outside the normal temperature range more

than 0.15 seconds, CHAG and the DONE pin is high impedance output state.

When the battery charger not received, the charger will quickly charge the output capacitor to the constant voltage value, as the

battery voltage detection Kelvin FB pin input leakage current, FB pin and the BAT pin voltage will slowly down to recharge

threshold, so the FB pin and the BAT pin voltage is 150mv to form a ripple waveform, while CHAG output pulse signal that there

is no battery installed. When the battery BAT pin external connectors for the 4.7uF capacitor, the pulse period of about 2Hz. The

following table lists CHAG and the DONE pin status in each case:

State

Charge

Full

Without Battery

Error

CHAG

Always bright

Always off

Flashing

Always off

DONE

Always off

Always bright

Always bright

Always off

Note: 1. CHAG flicker frequency with external capacitor when not connect battery, generally recommended 4.7uF.The greater

the capacitance, the smaller frequency flicker.

2. The error situation: Beyond the operating temperature range (temperature too high or too low), Iset side vacant, Vin

<Vbat, Vin <3.8V and so on.