MIC79110_07 Datasheet, PDF(11/14 Page) Micrel Semiconductor – Simple 1.2A Linear Li-Ion Battery Charger

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MIC79110_07 Datasheet, PDF (11/14 Pages) Micrel Semiconductor – Simple 1.2A Linear Li-Ion Battery Charger

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Micrel, Inc.

Simple Charger - External Trigger to Reset Charge

Cycle reset

Reset charge cycle.

RSET

SNS

BAT

VIN

GND

Reoc

DEOC

AEOC

VIN

CDELAY

0.1ÂµF

The VIN voltage steps up to a voltage greater than VBAT.

When VIN is below VBAT, the IBAT current is near zero and

the reverse shutoff circuit is turning the charge to the

battery off. The IBAT slowly increases as VIN rises above

VBAT. DEOC is pulled low when the IBAT current is above

the Ieoc current set by REOC. When the DEOC is low, the

shutdown pin is also forced low and helps discharge

CSD. When the VBAT reaches the set voltage, the IBAT

begins to slowly drop. When the IBAT is less than the IEOC

threshold, the DEOC output goes high impedance,

indicating end-of-charge. When an external signal is

applied to the gate, the external NCH pulls the SD and

DEOC pins to ground. This restarts the charging process.

MIC79110

External Trigger to Reset Charger

1. VIN steps up to a voltage greater than VBAT.

2. SD held low by CSD until active high DEOC pulls

shutdown low.

3. DEOC releases SD, resistor pull-up from SD pin,

VIN pulls VSD to VIN.

4. An external signal applied to the gate of the

external NCH pulls SD pin-to-ground.

5. IBAT is near zero (2 to 4ÂµA) because VIN is below

VBAT and the reverse shutoff circuit is turning the

charge to the battery off.

6. IBAT is decreased as VBAT approaches VBAT set

volt-age. IBAT decreases below the DEOC

threshold and DEOC is released high allowing VSD

to go high.

7. External NCH turns part on, after a small delay

IBAT turns on.

8. Active high DEOC pin goes high because of

reverse shutoff. DEOC remains high until IBAT

exceeds DEOC threshold, then goes low.

9. IBAT decreases below (see #5) DEOC threshold.

10. Active low DEOC is high because VIN is below

VBAT and reverse shutoff holds DEOC comparator

off. As VIN increases above VBAT, the reverse

volt-age shutoff turns off, DEOC comparator

becomes active. While IBAT is below DEOC

threshold DEOC active low goes low, when IBAT

exceeds DEOC threshold IBAT goes high.

11. Legitimate Activation of active low DEOC until SD

shuts down part and DEOC AL (active low) goes

high.

October 2007

M9999-102507

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