MIC79110 datasheet(10/10 Pages) MICREL

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MIC79110

Micrel

M9999-072004

July 2004

Simple Charger - External Trigger to Reset Charge

Cycle reset

200Ω

2kΩ

VIN

RSET

VSENSE

VBAT

VIN

GND

REOC

DEOC

ACHG

1MΩ

CDELAY

0.1µF

Reset charge cycle.

The V

IN 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 I

BAT slowly increases as VIN rises above VBAT. DEOC is

pulled low when the Ibat current is above the Ieoc current set

by R

EOC. When the DEOC is low, the shutdown pin is also

forced low and helps discharge C

SD. When the VBAT reaches

the set voltage, the Ibat begins to slowly drop. When the Ibat

is less than the I

EOC threshold, the DEOC output goes high

impedance, indicating end-of-charge. When an external sig-

nal is applied to the gate, the external N

CH pulls the SD and

DEOC pins to ground. This restarts the charging process.

External Trigger to Reset Charge Cycle Reset

1 - V

IN steps up to a voltage greater than VBAT.

2 - SD held low by C

SD until active high DEOC pulls

shutdown low.

3 - Deoc releases SD, resistor pull-up from SD pin'vo

IN pulls VSD to VIN.

4 - An external signal applied to the gate of the

external N

CH pulls SD pin-to-ground.

5 - Ibattery is near zero (2 to 4µA) because VIN is

below V

BAT and the reverse shutoff circuit is turn-

ing the charge to the battery off.

6 - I

BAT is decreased as VBAT approaches VBAT set

voltage. I

BAT decreases below the DEOC threshold

and D

EOC is released high allowing VSD to go high

7 - External N

CH turns part on, after a small delay IBAT

turns on.

8 - Active high DEOC pin goes high because of

reverse shutoff. D

EOC remains high until IBAT ex-

ceeds D

EOC threshold, then goes low.

9 - I

BAT decreases below (see #5) DEOC threshold.

10 - Active low D

EOC is high because VIN is below

BAT and reverse shutoff holds DEOC comparator

off. As V

IN increases above VBAT, the reverse

voltage shutoff turns off, D

EOC comparator be-

comes active. While I

BAT is below DEOC threshold

EOC active low goes low, when IBAT exceeds

EOC threshold IBAT goes high.

11 - Legitimate Activation of active low D

EOC until SD

shuts down part and D

EOC AL (active low) goes

high.

Vin

VSD

Vbat set voltage

Vbat

SD threshold

Vgate

Ibattery

Active high DEOC pin

Active low DEOC pin

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