ADP3500

REV.PrP 2/6/02

- 15 -

Reset sequence runs

A

Baseband sets Charge Voltage

Baseband sets MVBAT gain

Baseband Enables

Full charge current?

(CHI=1?)

N

Y

Low Current Charge: OFF

SetFullcurrent charge

(150mV on Rsense)

Baseband

CHEN=0?

N

Y

Charging Terminated

CHI=0: Full current charge OFF

CHI=1: Full current charge ON

Figure 7. Charger flow chart B

1.2.3.

Charger Detect function

The ADP3500 will detect that a charging adapter has been applied when the voltage at the ADAPTER pin exceeds the voltage at

BATSNS. The ADAPTER pin voltage must exceed the BVS voltage by a small positive offset. This offset has hysteresis to prevent

jitter at the detection threshold. The charger detection comparator will set the Charger_Detect flag in the 20h register and generate an

interrupt to the system. If the ADAPTER input voltage drops below the detection threshold, charging will stop automatically and the

Charger_Detect flag will be cleared and generate an interrupt also.

1.2.4.

DDLO function and operation

The ADP3500 contains a comparator that will lock out system operation if the battery voltage drops to the point of deep discharge.

When the battery voltage exceeds 2.675 V, the reference will start as will the sub-LDO 3b. If the battery voltage drops below the

hysteresis level, the reference and LDO's will be shut down, if for some reason they are still active. Since LDO1 will be in deep

dropout and well below the voltage detector threshold at this point, the reset generator will have already shut down the rest of the

system via RESET+, RESETOUT-, and RSTDELAY-.

If a charging adapter has been applied to the system, the DDLO comparator will force the charging current to trickle charge if the

battery is below the DDLO threshold. During this time, the charging current is limited to 5 mA. When the battery voltage exceeds

the upper threshold, the low current charging is enabled, which allows 55 mV (typical) across the external charge current sense

resistor. See also Figure 6, the Battery Charger Flowchart.

1.3 MVBAT

The ADP3500 provides a scaled buffered output voltage for use in reading the battery voltage with an A/D converter. The battery

voltage is divided down to be nominally 2.600 V at full scale battery of 4.35 V. To assist with calibrating out system errors in the

PRELIMINARY TECHNICAL DATA