ISL9216IRZ datasheet(23/34 Pages) RENESAS

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ISL9216, ISL9217

FN6488 Rev 1.00

Page 23 of 34

November 2, 2007

consumption. It must be activated by the external

microcontroller for it to operate. The circuit works by internally

connecting the VMON pin to VSS through a resistor. The circuit

operates as shown in Figure 4.

In a typical pack operation, when an overcurrent or short circuit

event happens, the DFET turns off, opening the battery circuit

to the load. At this time, the RL is small and the load monitor is

initially off. In this condition, the voltage at VMON could rise to

nearly the pack voltage. However, since in most configurations,

this voltage would exceed the maximum limits on the VMON

pin, a series zener diode is required.

Once the power FETs turn off, the microcontroller activates the

load monitor by setting the LDMONEN bit. This turns on an

internal FET that adds a pull-down resistor to the load monitor

circuit. While still in the overload condition the combination of

the load resistor, an external adjustment resistor (R1), the

zener diode, and the internal load monitor resistor form a

voltage divider. R1 is chosen so that when the load is released

to a sufficient level, the LDFAIL condition is reset.

OVER-TEMPERATURE SAFETY FUNCTIONS

External Temperature Control

The external temperature is monitored by using a voltage

divider consisting of a fixed resistor and a thermistor. This

divider is powered by the ISL9216 TEMP3V output. This output

is normally controlled so it is on for only short periods to

minimize current consumption.

Without microcontroller intervention, the ISL9216 continuously

turns on TEMP3V output (and the external temperature

monitor) for 5ms every 640ms. In this way, the external

temperature is monitored even if the microcontroller is asleep.

If the ATMPOFF bit is set, this automatic temperature scan is

turned off.

When the TEMP3V output turns on, the ISL9216 waits 1ms for

the temperature reading to stabilize, then compares the

external temperature voltage with an internal voltage divider

that is set to TEMP3V/13. When the thermistor voltage is

below the reference threshold after the delay, an external

temperature fail condition exists. To set the external over-

temperature limit, set the value of RX resistor to the 12 times

the resistance of the thermistor at the over-temperature

threshold.

The TEMP3V output pin also turns on when the microcontroller

sets the AO3:AO0 bits to select that the external temperature

voltage. This causes the TEMPI voltage to be placed on AO and

activates (after 1ms) the over-temperature detection. As long as

the AO3:AO0 bits point to the external temperature, the

TEMP3V output remains on.

Because of the manual scan of the temperature, it may be

desired to turn off the automatic scan, although they can be

used at the same time without interference. To turn off the

automatic scan, set the ATMPOFF bit.

The microcontroller can over-ride both the automatic

temperature scan and the microcontroller controlled

temperature scan by setting the TEMP3ON configuration bit.

This turns on the TEMP3V output to keep the temperature

control voltage on all the time, for a continuous monitoring of

an over-temperature condition. This likely will consume a

significant amount of current, so this feature is usually used for

special or test purposes.

Protection

As a default, when the ISL9216 detects an internal or external

over-temperature condition, the FETs are turned off, the cell

balancing function is disabled, and the IOT bit or XOT bit

(respectively) is set.

Turning off the FETs in the event of an over-temperature

condition prevents continued discharge or charge of the cells

when they are over heated. Turning off the cell balancing in the

event of an over-temperature condition prevents damage to

the IC in the event too many cells are being balanced, causing

too much power dissipation in the ISL9216.

In the event of an automatic over-temperature condition, cell

balancing is prevented and FETs are held off until the

temperature drops back below the temperature recovery

threshold. During this temperature shutdown period, the

635ms

5ms

FIGURE 5. EXTERNAL TEMPERATURE MONITORING AND

CONTROL (ISL9216 ONLY)

RGO

TEMP3V

TEMPI

VSS

I2C

MUX

I2C

TEMP

MONITOR

TEMP FAIL

INDICATOR

VSS (ON)

TMP3ON

AO3:AO0

DECODE

OSC

ATMPOFF

µC

XOT

1ms

DELAY

EXTERNAL

EXT TEMP

ISL9216

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