12.3 UNDER-VOLTAGE CUT-OFF

Two thresholds for cell under-voltage detection are used to prevent the cell from being discharged below levels that could cause

irreversible damage. The higher level, Primary Under-Voltage, is designated V

values are 2.350V and 1.98V respectively. When the V

below V

τ

with no time delay if the cell voltage drops below V

In sleep mode, all of the sequential logic is reset to a standby state. The safety shunt circuits are still powered up in order to

protect the chip and cell from an accidental path for high energy to the V

off).

Operating Current Parametric Specs

Unless otherwise noted, the following specifications apply over the Normal Temperature Range.

Specification

Test Conditions

Min

Typ

Max

Units

Quiescent Current w/no external power supply

“I

V

No Load at Radio B+, I

V

-20

30

µA

Quiescent Current w/no external power supply

“I

V

No Load at Radio B+, I

V

-

-

50

µA

Sleep Mode Current “I

Sleep mode AND V

No Load at Radio B+

V

-

9.0

15

µA

Sleep Mode Current “I

Temperature Range

Sleep mode AND V

No Load at Radio B+

V

-

-

20

µA

Primary Under Voltage “V

Time delay entry into sleep mode =

τ

PUV

2.275

2.350

2.425

V

Hibernation Delay “

τ

223264

ms

Primary Under Voltage Delay “

τ

446484

ms

Secondary Under Voltage “V

No delay entry into sleep mode

1.90

1.98

2.06

V

“V

∆

100

200

300

mV

12.4 POWER CUT OPERATION

A power cut is defined as momentary loss of contact between the battery/cell and the phone circuitry, typically caused by contact

bounce. During a power cut, the connection between the cell’s positive terminal and the IC’s CELL pin may be lost as well as the

ground connection between the cell’s negative terminal and the IC’s ground pins. During Power Cut the IC will go into the sleep

mode. Once the connection is re-established and the cell voltage is greater than V

up its internal circuitry and allow the operations (charging and discharging) to continue. A power cut is differentiated from an

under-voltage condition by monitoring the cell voltage level.

12.5 HIBERNATION MODE

battery. This is generally desired except when the phone is stored for a long time without use and without being charged. When

hibernation mode is enabled, then M4 is opened so that the battery cell will discharge only due to the consumption of this IC and

not because of any Radio B+ current consumption. When Hibernation is enabled, the IC will be put into ‘sleep’ which allows the

IC to have a smaller quiescent current when compared to ‘normal’ mode.

Hibernation mode is entered when HIB_EN is held high for a debounce period of 32 ms.

Hibernation mode is exited and M4 subsequently closed when a charger is connected to LM3655 or when the HIB_DISB input

pin goes low.

13.0 Safety Functions

13.1 INPUT OVER-VOLTAGE PROTECTION

13.1.1 Normal Operation (Q1 Control)

Under normal conditions, the Q1 pass device prevents excessively high voltages from reaching RADIO_B+. In the case of

full-rate charging, the external supply voltage will normally collapse to a level just above the cell voltage as the supply current limit

is reached. As charge current is reduced, the supply voltage may increase, but the voltage difference is dropped across Q1 as

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