ISL9216IRZ datasheet(21/34 Pages) RENESAS

21 / 34 page

ISL9216, ISL9217

FN6488 Rev 1.00

Page 21 of 34

November 2, 2007

Device Description

Design Theory

Instructed by the microcontroller, the ISL9216 and ISL9217

chip set performs cell voltage monitoring and cell balancing

operations. The ISL9216 has automatic overcurrent and short

circuit monitoring, and shut-down with built-in selectable time

delays. The ISL9216 also provides automatic turn off of the

power FETs and cell balancing FETs in an over-temperature

condition. All automatic functions of the ISL9216 can be turned

off and the microcontroller can manage the operations through

software.

Battery Connection

The ISL9216 and ISL9217 support packs of 8 to 12 series

connected Li-ion cells. Connection guidelines for each cell

combination are shown in Figure 1.

System Power-Up/Power-Down

The ISL9216 and ISL9217 power-up when the voltages on

their VCELL1, VCELL2, VCELL3, and VCC pins all exceed

their POR threshold. At this time, the devices each wake-up

and turn on their RGO output.

The regulator circuit provides 3.3VDC at pin RGO. It does this

by using a control voltage on the RGC pin to drive an external

NPN transistor (See Figure 2). For the ISL9216, the transistor

should have a beta of at least 70 to provide ample current to

the device and external circuits and should have a VCE of

greater than 60V (preferably higher) for a 12 cell pack. For the

ISL9217, the transistor selection is not as critical because it will

likely not drive any external circuits, however, it should be rated

with a VCE greater than 50V.

The voltage at the emitter of the NPN transistor is monitored

and regulated to 3.3V by the control signal RGC. RGO also

powers most of the ISL9216 and ISL9217 internal circuits. A

500

 resistor is recommended in the collector of each NPN

transistor to minimize initial current surge when the regulator

turns on.

Once powered up, the devices remain in a wake-up state until

put to sleep by the microcontroller (typically when the cells

drop too low in voltage) or until the VCELL1, VCELL2,

VCELL3, or VCC voltages drop below their POR threshold.

WKUP Pin Operation

There are two ways to design a wake-up of the ISL9216. In an

active LOW connection (WKPOL = ’0’ - default), the device

wakes up when a charger is connected to the pack. This pulls

the WKUP pin low when compared to a reference based on the

VCELL1 voltage. In an active HIGH connection (WKPOL = ‘1’)

the device wakes up when then WKUP pin is pulled high by a

connection through an external switch. See Figure 3.

Once the ISL9216 wakes up, the RGO powers up the

microcontroller. The microcontroller then wakes up the

ISL9217 by setting the WKUPR bit in the ISL9216. The

WKUPR pin of the ISL9216 connects to the ISL9217 WKUP

pin. When the ISL9216 WKUPR bit is set to “1”, the ISL9217

WKUP pin pulls low and the ISL9217 wakes up. Because of

this operation, it is important that the WKPOL bit of the

ISL9217 remain in the default state (ISL9217 WKPOL = 0).

Protection Functions

In the default, recommended condition, the ISL9216

automatically responds to discharge overcurrent, discharge

short circuit, charge overcurrent, internal over-temperature,

and external over-temperature. The designer can set optional

over-ride conditions that allow the response to be dictated by

the microcontroller. These are discussed in the following

section.

RGC

RGO

VSS

VCC

FIGURE 2. VOLTAGE REGULATOR CIRCUITS

RGC

RGO

VSS

VCC

3.3V

GND

500

ISL9216

FIGURE 3. WAKE-UP CONTROL CIRCUITS

VSS

330k*

* INTERNAL RESISTOR

ONLY CONNECTED WHEN

WKPOL = 1.

WKUP

WKPOL

WKUP

(STATUS)

(CONTROL)

WAKE-UP

CIRCUITS

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