ISL9211AIRU48XZ-T Intersil, ISL9211AIRU48XZ-T Datasheet - Page 9

• Manufacturer Part Number: ISL9211AIRU48XZ-T
• Description: IC SAFETY CIRCUIT CHARGE 8UTDFN
• Manufacturer: Intersil

Specifications of ISL9211AIRU48XZ-T

• Function: Battery Monitor
• Battery Chemistry: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.3 V ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-UFDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

in the sensing FET is forced to match the value
programmed by I
with the resistor R
The size of the power FET Q
the sensing FET. Therefore, when the current in the
power FET is 31,250 times the current in the sensing FET,
the drain voltage of the power FET falls below that of the
sensing FET. The comparator CP2 then outputs a signal
to turn off the power FET. where the 0.8V is the regulated
reference voltage at the ILIM pin. The OCP comparator
CP2 has a built-in 180µs delay to prevent false triggering
by transient signals. The OCP function also has a 4-bit
binary counter that accumulates during an OCP event.
When the total count reaches 16, the power NFET is
turned off permanently until the input power is recycled
or the enable pin is toggled. Figures 7 and 8 illustrate the
waveforms during the power-up when the output is
shorted to ground.
Internal Over-Temperature Protection
The ISL9211A monitors its own internal temperature to
prevent thermal failures. When the internal temperature
reaches +150°C, the IC turns off the N-channel power
MOSFET. The IC does not resume operation until the
internal temperature drops below +110°C.
Fault Indication Output
The FAULT pin is an open-drain output that indicates a
LOW signal when any of the three fault events happens.
This provides a signal to the microprocessor to take
further action to enhance the safety of the charging
system.
Applications Information
The ISL9211A is designed to meet the “Lithium-Safe”
criteria when operating together with a qualified Li-ion
battery charger. The “Lithium-Safe” criteria requires the
charger output to fall within the green region shown in
Figure 14 under normal operating conditions and NOT to
fall in the red region when there is a single fault in the
charging system. Taking into account the safety circuit in
a Li-ion battery pack, the charging system is allowed to
R
(kΩ)
82.5
61.9
49.9
41.2
35.7
31.6
24.9
22.6
28
LIM
LIM
LIM
(mA)
1000
1100
OCP
300
400
500
600
700
800
900
pin. The OCP threshold can be set
as shown in Table 2.
TABLE 2.
9
1
is 31,250 times the size of
R
(kΩ)
19.1
16.5
15.4
12.4
11.3
10.5
9.53
LIM
21
14
(mA)
1200
1300
1400
1500
1600
1700
1800
1900
2000
OCP
ISL9211A
have two faults without creating hazardous conditions for
the battery cell. The output of the Li-ion charger, such as
the ISL6292C, has a typical I-V curve shown with the
blue lines under normal operation, which is within the
green region. The function of the ISL9211A is to add a
redundant protection layer such that, under any single
fault condition, the charging system output does not
exceed the I-V limits shown with the red lines. As a
result, the charging system adopting the ISL9211A and
the ISL6292C chip set can easily pass the “Lithium-Safe”
criteria test procedures.
The ISL9211A is a simple device that requires only three
external components, in addition to the ISL6292 charger
circuit, to meet the “Lithium-Safe” criteria, as shown in
the “Typical Application Circuit” on page 1. The selection
of the current limit resistor R
Protection (OCP)” on page 8.
R
The R
battery terminal, in case the ISL9211A fails. The
recommended value should be between 200kΩ to 1MΩ.
With 200kΩ resistance, the worst case current flowing
from the VB pin to the charger output is shown in
Equation 1, assuming the VB pin voltage is 24V under a
failure mode and the battery voltage is 4.2V.
(
Such a small current can be easily absorbed by the bias
current of other components in the handheld system.
Increasing the R
but at the same time increases the error for the 4.34V
battery OVP threshold.
The error of the battery OVP threshold is the original
accuracy at the VB pin given in the “Electrical
Specifications” table on page 4 plus the voltage built
across the R
leakage current is less than 20nA, as given in the
“Electrical Specifications” table on page 4. With the
200kΩ resistor, the worst-case additional error is 4mV
and with a 1MΩ resistor, the worst-case additional error
is 20mV.
24V 4.2V
1000
VB
FIGURE 14. LITHIUM-SAFE OPERATING REGIONS
–
0
Selection
VB
prevents a large current from the VB pin to the
)
⁄
(
VB
200kΩ
1
ISL9211A
LIMITS
ISL6292C
LIMITS
by the VB pin leakage current. The VB pin
VB
)
value reduces the worst case current,
=
2
99μA
BATTERY VOLTAGE (V)
ILIM
3
is given in “Overcurrent
4
August 25, 2010
5
FN6702.1
(EQ. 1)
6