ISL94208 Datasheet, PDF (3/37 Pages) Intersil Corporation – 4- to 6-Cell Li-ion Battery Management Analog Front-End

ISL94208
Pin Descriptions (Continued)
PIN NUMBER
16
17
18
19
20
21
22
23
25
24
26
27
28
29
PIN NAME
VSS
ISREF
DSENSE
CSENSE
DFET
CFET
VMON
AO
TEMP3V
TEMPI
RGO
RGC
WKUP
SDA
DESCRIPTION
Ground. This pin connects to the most negative terminal in the battery string.
Current sense reference. This input provides a separate reference point for the charge and discharge current
monitoring circuits. WIth a separate reference connection, it is possible to minimize errors that result from
voltage drops on the ground lead when the load is drawing large currents. If a separate reference is not
necessary, connect this pin to VSS.
Discharge current sense monitor. This input monitors the discharge current by monitoring a voltage across a
sense resistor, or across the discharge path FET, or by using a FET with a current sense pin. The voltage on this
pin is measured with reference to ISREF.
Charge current sense monitor. This input monitors the charge current by monitoring a voltage across a sense
resistor, or the voltage across the charge path FET, or by using a FET with a current sense pin. The voltage on
this pin is measured with reference to ISREF.
Discharge FET control. The ISL94208 controls the gate of a discharge path FET through this pin. The power FET
is an N-Channel device. The FET is turned on only by the microcontroller. The FET can be turned off by the
microcontroller, but the ISL94208 also turns off the FET in the event of an overcurrent or short circuit condition.
If the microcontroller detects an undervoltage condition on any of the battery cells, it can turn off the discharge
FET by controlling this output with a control bit.
Charge FET control. The ISL94208 controls the gate of a charge path FET through this pin. The power FET is an
N-Channel device. The FET is turned on only by the microcontroller. The FET can be turned off by the
microcontroller, but the ISL94208 also turns off the FET in the event of an overcurrent condition. If the
microcontroller detects an overvoltage condition on any of the battery cells, it can turn off the FET by controlling
this output with a control bit.
Discharge load monitoring. In the event of an overcurrent or short circuit condition, the microcontroller can
enable an internal resistor that connects between the VMON pin and VSS. When the FETs open because of an
overcurrent or short circuit condition and the load remains, the voltage at VMON will be near the VCC voltage.
When the load is released, the voltage at VMON drops below a threshold indicating that the overcurrent or short
circuit condition is resolved. At this point, the LDFAIL flag is cleared and operation can resume.
Analog multiplexer output. The analog output pin is used to monitor the cell voltages and temperature sensor
voltages. An external microcontroller selects the specific voltage being applied to the output by writing to a
control register.
Temperature monitor output control. This pin outputs a voltage to be used in a divider that consists of a fixed
resistor and a thermistor. The thermistor is located in close proximity to the battery cells. The TEMP3V output is
connected internally to the RGO voltage through a PMOS switch only during a measurement of the temperature,
otherwise the TEMP3V output is off. The TEMP3V output can be turned on continuously with a special control bit.
Microcontroller wake up control. The TEMP3V pin is also turned on when any of the DSC, DOC, or COC bits are
set. This can be used to wake up a sleeping microcontroller to respond to overcurrent conditions with its own
control mechanism.
Temperature monitor input. The voltage across a thermistor is monitored at this pin to determine the
temperature of the battery cells. When this input drops below TEMP3V/13, an external over-temperature
condition is reported. The TEMPI voltage can be fed to the AO output pin through an analog multiplexer to be
monitored by the microcontroller.
Regulated output voltage. This pin connects to the emitter of an external NPN transistor and works in
conjunction with the RGC pin to provide a regulated 3.3V. The voltage at this pin provides feedback for the
regulator and power for many of the ISL94208 internal circuits as well as providing the 3.3V output voltage for
the microcontroller and other external circuits.
Regulated output control. This pin connects to the base of an external NPN transistor and works in conjunction
with the RGO pin to provide a regulated 3.3V. The RGC output provides the control signal for the external
transistor to provide the 3.3V regulated voltage on the RGO pin.
Wake up voltage. This input wakes up the part when the voltage crosses a turn-on threshold (wake up is edge
triggered). The condition of the pin is reflected in the WKUP bit (the WKUP bit is level sensitive).
WKPOL bit = “1”: the device wakes up on the rising edge of the WKUP pin. Also, the WKUP bit is HIGH only when
the WKUP pin voltage > threshold.
WKPOL bit = “0”, the device wakes up on the falling edge of the WKUP pin. Also, the WKUP bit is HIGH only when
the WKUP pin voltage < threshold.
Serial Data. This is the bidirectional data line for an I²C interface. This pin should be pulled up to 3.3V using a
resistor.
3
FN8306.0
November 26, 2012