ISL9211AIRU48XZ-T Intersil, ISL9211AIRU48XZ-T Datasheet - Page 8

• 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

Typical Operating Performance
V
Theory of Operation
The ISL9211A is an integrated circuit (IC) optimized to
provide a redundant safety protection to a Li-ion battery
from charging system failures. The IC monitors the input
voltage, the battery voltage, and the charge current.
When any of the above three parameters exceeds its
limit, the IC turns off an internal N-channel MOSFET to
remove the power from the charging system. In addition
to the above protected parameters, the IC also monitors
its own internal temperature and turns off the N-channel
MOSFET when the temperature exceeds +150°C.
Together with the battery charger IC and the protection
module in a battery pack, the charging system has
triple-level protection from overcharging the Li-ion
battery and is two-fault tolerant. The ISL9211A protects
up to 26V input voltage.
Power-Up
The ISL9211A has a power-on reset (POR) threshold of
2.47V (max). Before the input voltage reaches the POR
threshold, the internal power NFET is off. Approximately
10ms after the input voltage exceeds the POR threshold,
the IC resets itself and begins the soft-start. The 10ms
delay allows any transients at the input during a hot
insertion of the power supply to settle down before the IC
starts to operate. The soft-start slowly turns on the
power NFET to reduce the inrush current as well as the
input voltage drop during the transition. The power-up
sequence is illustrated in Figure 1.
Input Overvoltage Protection (OVP)
The input voltage is monitored by the comparator CP1 in
the “Block Diagram” on page 2. CP1 has an accurate
reference of 1.2V from the bandgap reference. The OVP
threshold is set by the resistive divider consisting of R
and R
the CP1 outputs a logic signal to turn off the power NFET
within 1µs (see Figure 2) to prevent the high input
voltage from damaging the electronics in the handheld
IN
= 5V, T
2
. When the input voltage exceeds the threshold,
A
= +25°C, R
FIGURE 13. ON-RESISTANCE vs TEMPERATURE AT DIFFERENT INPUT VOLTAGES
ILIM
8
= 24.9kΩ, R
VB
= 200kΩ, Unless Otherwise Noted. (Continued)
350
300
250
200
150
100
50
0
-50 -30 -10
ISL9211A
1
TEMPERATURE (°C)
10
The test conditions for the Typical Operating Performance are:
30
system. The hysteresis for the input OVP threshold is
given in the “Electrical Specifications” table on page 4.
When the input overvoltage condition is removed, the
ISL9211A re-enables the output by running through the
soft-start, as shown in Figure 4. Because of the 10ms
second delay before the soft-start, the output is never
enabled if the input rises above the OVP threshold
quickly, as shown in Figure 5.
Battery Overvoltage Protection
The battery voltage OVP is realized with the VB pin. The
comparator CP3, as shown in the “Block Diagram” on
page 2, monitors the VB pin and issues an overvoltage
signal when the battery voltage exceeds the 4.34V
battery OVP threshold. The threshold has 30mV built-in
hysteresis. The comparator CP3 has a built-in 180µs
blanking time to prevent any transient voltage from
triggering the OVP. If the OVP situation still exists after
the blanking time, the power NFET is turned off. The
control logic contains a 4-bit binary counter that if the
battery overvoltage event occurs 16 times, the power
NFET is turned off permanently, as shown in Figure 6.
Recycling the input power will reset the counter and
restart the ISL9211A.
The resistor between the VB pin and the battery, R
shown in the “Typical Application Circuit” on page 1, is an
important component. This resistor provides a current
limit in case the VB pin is shorted to the input voltage
under a failure mode. The VB pin leakage current under
normal operation is negligible to allow a resistance of
200kΩ to 1MΩ be used.
Overcurrent Protection (OCP)
The current in the power NFET is limited to prevent
charging the battery with an excessive current. The
current is sensed using the voltage drop across the
power FET after the it is turned on. The reference of the
OCP is generated using a sensing FET Q
as shown in the “Block Diagram” on page 2. The current
4.3V
50
5.0V
3.0V
70
90
110 130
2
(Mirror to Q
August 25, 2010
FN6702.1
VB
, as
1
),