Intersil ISL9212 Charging system safety circuit Datasheet

ISL9212
®
Data Sheet
June 30, 2008
FN9280.2
Charging System Safety Circuit
Features
The ISL9212 is an integrated circuit (IC) optimized to provide
a Li-ion battery redundant safety protection from failures of a
charging system. The IC monitors the input voltage, the
battery voltage, and the charge current. When any of the
three parameters exceeds its limit, the IC turns off an internal
P-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 P-Channel MOSFET when the die temperature exceeds
+140°C. Together with the battery charger IC and the
protection module in a battery pack, the charging system
using the ISL9212 has triple-level protection and is two-fault
tolerant.
• Fully Integrated Protection Circuit for Three Protection
Variables
- User Programmable Overcurrent Protection Threshold
- Input Overvoltage Protection in Less Than 1µs
- Battery Overvoltage Protection
The IC is designed to turn on the internal PFET slowly to
avoid in-rush current at power-up but will turn off the PFET
quickly when input overvoltage is detected, in order to
remove the power before any damage occurs. The ISL9212
has a logic warning output to indicate the fault and an enable
input to allow the system to remove the input power.
Ordering Information
212Z
• High Accuracy Protection Thresholds
• Warning Output to Indicate the Occurrence of Faults
• Enable Input
• Thermal Enhanced TDFN Package
• Pb-Free (RoHS Compliant)
Applications
• Cell Phones
• Digital Still Cameras
• PDAs and Smart Phones
• Portable Instruments
TEMP.
RANGE
PART NUMBER
PART
(°C)
(Note)
MARKING
ISL9212IRZ*
• High Immunity of False Triggering Under Transients
PACKAGE
(Pb-free)
-40 to +85 12 Ld 4x3 TDFN
(0.75mm)
PKG.
DWG. #
L12.4x3A
• Desktop Chargers
Related Literature
• Technical Brief TB363 “Guidelines for Handling and
Processing Moisture Sensitive Surface Mount Devices
(SMDs)”
ISL9212EVAL1Z Evaluation Board
*Add “-T” suffix for tape and reel.
NOTE: These Intersil Pb-free plastic packaged products employ special
Pb-free material sets; molding compounds/die attach materials and
100% matte tin plate PLUS ANNEAL - e3 termination finish, which is
RoHS compliant and compatible with both SnPb and Pb-free soldering
operations. Intersil Pb-free products are MSL classified at Pb-free peak
reflow temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
• Technical Brief TB379 “Thermal Characterization of
Packaged Semiconductor Devices”
• Technical Brief TB389 “PCB Land Pattern Design and
Surface Mount Guidelines for QFN Packages”
Pinout
ISL9212
(12 LD 4x3 TDFN)
TOP VIEW
Typical Application Circuit
INPUT
VIN
OUT
C1
ISL6292
BATTERY
CHARGER
ISL9212
VB
ILIM
RVB
EN
RILIM
WRN
GND
1
BATTERY
PACK
VIN
1
12 NC
VIN
2
11 OUT
GND
3
WRN
4
9
ILIM
NC
5
8
VB
NC
6
7
EN
EPAD
10 OUT
+
NOTE: EPAD must be electrically connected to the GND pin.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2006, 2008. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.
ISL9212
Absolute Maximum Ratings (Reference to GND)
Thermal Information
Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 30V
Output and VB Pin (OUT, VB) (Note 1) . . . . . . . . . . . . . . -0.3V to 7V
Other Pins (ILIM, WRN, EN) . . . . . . . . . . . . . . . . . . . . -0.3V to 5.5V
ESD Rating
Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3000V
Machine Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300V
Thermal Resistance (Notes 2, 3)
θJA (°C/W)
θJC (°C/W)
4x3 TDFN Package . . . . . . . . . . . . . . .
41
3.5
Maximum Junction Temperature (Plastic Package) . . . . . . . +150°C
Maximum Storage Temperature Range . . . . . . . . . .-65°C to +150°C
Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3V to 6.5V
Operating Current Range. . . . . . . . . . . . . . . . . . . . . . . . . 0A to 1.5A
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and
result in failures not covered by warranty.
NOTES:
1. The maximum voltage rating for the VB pin under continuous operating conditions is 5.5V. All other pins are allowed to operate continuously at
the absolute maximum ratings.
2. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379.
3. θJC, “case temperature” location is at the center of the exposed metal pad on the package underside. See Tech Brief TB379.
Electrical Specifications
Typical values are tested at VIN = 5V and TA = +25°C, maximum and minimum values are guaranteed over the
recommended operating conditions, unless otherwise noted.
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
2.4
2.58
2.7
V
-
100
-
mV
When enabled
0.75
0.9
1.05
mA
When disabled
30
60
100
µA
6.65
6.8
7.0
V
-
60
100
mV
Input OVP Falling Threshold
6.55
-
-
V
Input OVP Propagation Delay
-
-
1
µs
POWER-ON RESET
Rising VIN Threshold
VPOR
POR Hysteresis
VIN Bias Current
IVIN
VIN Bias Current
PROTECTIONS
Input Overvoltage Protection (OVP)
VOVP
Input OVP Hysteresis
Overcurrent Protection
IOCP
0.93
1.0
1.07
A
Overcurrent Protection Blanking Time
BtOCP
VVB = 3V, RILIM = 25kΩ
-
170
-
µs
Battery Overvoltage Protection Threshold
VBOVP
4.325
4.4
4.475
V
-
75
-
mV
4.225
-
-
V
-
180
-
µs
-
-
20
nA
Over-Temperature Protection Rising Threshold
-
140
-
°C
Over-Temperature Protection Falling Threshold
-
90
-
°C
1.5
-
-
V
Battery OVP Threshold Hysteresis
Battery OVP Falling Threshold
Battery OVP Blanking Time
BtBOVP
VB Pin Leakage Current
VVB = 4.4V
LOGIC
EN Input Logic HIGH
EN Input Logic LOW
EN Internal Pull-Down Resistor
WRN Output Logic Low
Sink 5mA current
WRN Output Logic High Leakage Current
-
-
0.4
V
100
200
400
kΩ
-
0.35
0.8
V
-
-
1
µA
-
170
280
mΩ
POWER MOSFET
ON-Resistance
rDS(ON)
2
4.6V < VIN < 6.5V
FN9280.2
June 30, 2008
ISL9212
Pin Descriptions
VB (Pin 8)
VIN (Pins 1, 2)
Battery voltage monitoring input. This pin is connected to the
battery pack positive terminal via an isolation resistor.
The input power source. The VIN can withstand 30V input.
ILIM (Pin 9)
GND (Pin 3)
System ground reference.
Overcurrent protection threshold setting pin. Connect a
resistor between this pin and GND to set the OCP threshold.
WRN (Pin 4)
OUT (Pins 10, 11)
WRN is an open-drain logic output that turns LOW when any
protection event occurs.
Output pin.
EPAD
NC (Pins 5, 6, 12)
The exposed pad at the bottom of the DFN package for
enhancing thermal performance. Must be electrically
connected to the GND pin.
No connection and must be left floating.
EN (Pin 7)
Enable input. Pull this pin to low or leave it floating to enable
the IC and force it to high to disable the IC.
Typical Applications
INPUT
VIN
OUT
C1
ISL6292
BATTERY
CHARGER
PART
ISL9212
VB
ILIM
RVB
RILIM
25kΩ
RVB
200kΩ to 1MΩ
1µF/16V X5R ceramic capacitor
BATTERY
PACK
WRN
GND
RILIM
C1
+
EN
DESCRIPTION
Block Diagram
INPUT
OUT
VIN
ISL6292
BATTERY
CHARGER
Q1
Q2
POR
PRE-REG
REF
Q3
ILIM
FET
DRIVER
RILIM
CP2
R1
EA
0.8V
CP1
CP3
LOGIC
VB
R VB
1.2V
R2
R3
Q4
R4
Q5
WRN
GND
BUF
+
R5
EN
FIGURE 1. BLOCK DIAGRAM
3
FN9280.2
June 30, 2008
ISL9212
Typical Operating Performance
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = +25°C,
RILIM = 25.5kΩ, RVB = 200kΩ, Unless Otherwise Noted.
VIN (2V/DIV)
VIN
(2V/div)
VIN
VIN(1V/DIV)
(1V/div)
OUT (1V/DIV)
OUT
(1V/div)
OUT
OUT(2V/DIV)
(2V/div)
Load
LOAD Current
CURRENT
(200mA/div)
200mA/DIV
WRN
(5V/div)
WRN (5V/DIV)
TIME:
Time:5ms/DIV
5ms/div
FIGURE 2. CAPTURED WAVEFORMS FOR POWER-UP. THE
OUTPUT IS LOADED WITH A 10Ω RESISTOR
TIME:
Time:2µs/DIV
2μs/div
FIGURE 3. CAPTURED WAVEFORMS WHEN THE INPUT
VOLTAGE STEPS FROM 6.5V TO 10.5V
Time:200ms/DIV
200ms/div
TIME:
VIN (2V/DIV)
VIN
(2V/div)
VIN (2V/DIV)
(2V/div)
VIN
OUT
(2V/div)
OUT (2V/DIV)
OUT
OUT(2V/DIV)
(2V/div)
WRN (5V/DIV)
WRN
(5V/div)
WRN
(5V/div)
WRN (5V/DIV)
TIME:
Time:5ms/DIV
5ms/div
FIGURE 4. CAPTURED WAVEFORMS WHEN THE INPUT
GRADUALLY RISES TO THE INPUT
OVERVOLTAGE THRESHOLD
VIN
(2V/div)
VIN (2V/DIV)
FIGURE 5. TRANSIENT WHEN THE INPUT VOLTAGE STEPS
FROM 7.5V TO 6.5V
Time:
20s/div
TIME: 20s/DIV
VIN (1V/DIV)
VIN
(1V/div)
VB(1V/DIV)
(1V/div)
VB
OUT(2V/DIV)
(2V/div)
OUT
ILIM
ILIM(1V/DIV)
(1V/div)
OUT
(1V/div)
OUT (1V/DIV)
WRN (5V/DIV)
WRN
(5V/div)
WRN (5V/DIV)
500µs/DIV
Time:
500μs/div
WRN
(5V/div) TIME:
FIGURE 6. TRANSIENT WAVEFORMS WHEN INPUT STEPS
FROM 0V TO 9V
4
FIGURE 7. BATTERY OVERVOLTAGE PROTECTION. THE IC
IS LATCHED OFF AFTER 16 COUNTS OF
PROTECTION. VB VOLTAGE VARIES BETWEEN
4.3V TO 4.5V
FN9280.2
June 30, 2008
ISL9212
Typical Operating Performance
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = +25°C,
RILIM = 25.5kΩ, RVB = 200kΩ, Unless Otherwise Noted. (Continued)
TIME: 200ms/DIV
Time:
200ms/div
Time:
10ms/div
TIME: 10ms/DIV
VIN(1V/DIV)
(1V/div)
VIN
VIN
(1V/div)
VIN (1V/DIV)
OUT
(1V/div)
OUT (1V/DIV)
Load
LOAD Current
CURRENT
500mA/DIV
(500mA/div)
LOAD
Load CURRENT
Current
500mA/DIV
(500mA/div)
OUT (1V/DIV)
OUT
(1V/div)
WRN (5V/DIV)
WRN
(5V/div)
WRN (5V/DIV)
WRN
(5V/div)
FIGURE 8. POWER-UP WAVEFORMS WHEN OUTPUT IS
SHORT-CIRCUITED
FIGURE 9. ZOOMED-IN VIEW OF FIGURE 8 (BLUE: LOAD
CURRENT; PINK: OUT PIN VOLTAGE)
1200
1000
6.5V/ENABLED
1000
800
800
CURRENT (µA)
INPUT BIAS CURRENT (µA)
900
ENABLED
600
400
DISABLED
700
30V/ENABLED
600
500
400
300
200
200
4.3V/ENABLED
5V/ENABLED
30V/DISABLED
6.5V/DISABLED
5V/DISABLED
4.3V/DISABLED
100
0
0
5
10
15
20
25
30
0
-50
35
-20
10
40
70
100
130
TEMPERATURE (°C)
INPUT VOLTAGE (V)
FIGURE 10. INPUT BIAS CURRENT vs INPUT VOLTAGE
WHEN ENABLED AND DISABLED
FIGURE 11. INPUT BIAS CURRENT AT DIFFERENT INPUT
VOLTAGES WHEN ENABLED AND DISABLED
6.95
2.60
2.58
6.90
RISING THRESHOLD
RISING THRESHOLD
6.85
VOVP (V)
VPOR (V)
2.56
2.54
2.52
6.80
6.75
2.50
FALLING THRESHOLD
2.46
-50
FALLING THRESHOLD
6.70
2.48
-20
10
40
70
100
TEMPERATURE (°C)
FIGURE 12. VPOR vs TEMPERATURE
5
130
6.65
-50
-20
10
40
70
100
130
TEMPERATURE (°C)
FIGURE 13. INPUT OVERVOLTAGE PROTECTION
THRESHOLDS vs TEMPERATURE
FN9280.2
June 30, 2008
ISL9212
Typical Operating Performance
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = +25°C,
RILIM = 25.5kΩ, RVB = 200kΩ, Unless Otherwise Noted. (Continued)
1050
1040
200
CURRENT
LIMIT = 1A
195
190
1030
185
1010
BtOCP (µs)
IOCP (mA)
1020
6.5V
5V
1000
990
175
170
165
980
160
3V
4.3V
970
960
-50
180
-20
155
10
40
70
100
150
-50
130
-20
TEMPERATURE (°C)
FIGURE 14. OVERCURRENT PROTECTION THRESHOLDS vs
TEMPERATURE AT VARIOUS INPUT VOLTAGES
130
4.42
510
4.41
4.3V
4.40
505
6.5V
RISING THRESHOLDS FOR
4.5V, 5V AND 6.5V INPUT
4.39
VBOVP (V)
500
IOCP (mA)
100
FIGURE 15. OVERCURRENT PROTECTION BLANKING TIME
vs TEMPERATURE
515
495
490
3V
485
4.38
4.37
4.36
FALLING THRESHOLDS FOR
4.5V, 5V AND 6.5V INPUT
4.35
480
4.34
475
4.33
5V
4.32
-50
470
-50
-20
10
40
70
100
130
-20
FIGURE 16. OVERCURRENT PROTECTION THRESHOLDS vs
TEMPERATURE AT VARIOUS INPUT VOLTAGES
40
70
100
130
FIGURE 17. BATTERY VOLTAGE OVP THRESHOLDS vs
TEMPERATURE AT VARIOUS INPUT VOLTAGES
3.0
200
VB PIN LEAKAGE CURRENT (nA)
195
190
185
180
175
170
165
160
155
150
-50
10
TEMPERATURE (°C)
TEMPERATURE (°C)
BtBOVP (µs)
10
40
70
TEMPERATURE (°C)
-20
10
40
70
100
TEMPERATURE (°C)
FIGURE 18. BATTERY OVP BLANKING TIME
6
130
TESTED AT 5V
2.5
2.0
1.5
1.0
0.5
0
-50
-20
10
40
70
100
130
TEMPERATURE (°C)
FIGURE 19. VB PIN LEAKAGE CURRENT vs TEMPERATURE
FN9280.2
June 30, 2008
ISL9212
Typical Operating Performance
The test conditions for the Typical Operating Performance are: VIN = 5V, TA = +25°C,
RILIM = 25.5kΩ, RVB = 200kΩ, Unless Otherwise Noted. (Continued)
250
EN PIN INTERNAL PULL-DOWN (kΩ)
2.0
1.8
EN THRESHOLD (V)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
-50
-20
10
40
70
100
240
230
220
210
200
190
180
170
160
150
130
-50
-20
10
40
70
100
130
TEMPERATURE (°C)
TEMPERATURE (°C)
FIGURE 20. EN INPUT THRESHOLD vs TEMPERATURE
FIGURE 21. EN PIN INTERNAL PULL-DOWN RESISTANCE
0.35
0.30
rDS(ON) (Ω)
0.25
0.20
0.15
0.10
0.05
FROM TOP TO BOTTOM VIN AND ILOAD ARE:
3V/1.5A, 3V/0.5A, 4.6V/1.5A, 4.6V/0.5A,
5V/1.5A, 5V/0.5A, 6.5V/1.5A, AND 6.5V/0.5A
0
-50
-20
10
40
70
TEMPERATURE (°C)
100
130
FIGURE 22. ON-RESISTANCE vs TEMPERATURE AT DIFFERENT INPUT VOLTAGES AND LOAD CURRENTS
Theory of Operation
Power-Up
The ISL9212 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
P-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
P-Channel MOSFET when the temperature exceeds +140°C.
Together with the battery charger IC and the protection
module in a battery pack, the charging system has triple-level
protection from over-charging the Li-ion battery and is
two-fault tolerant. The ISL9212 protects up to 30V input
voltage.
The ISL9212 has a power-on reset (POR) threshold of 2.6V
with a built-in hysteresis of 100mV. Before the input voltage
reaches the POR threshold, the internal power PFET 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
PFET to reduce the in-rush current as well as the input
voltage drop during the transition. The power-up behavior is
illustrated in Figure 2.
7
Input Overvoltage Protection (OVP)
The input voltage is monitored by the comparator CP1 in the
Block Diagram (Figure 1). CP1 has an accurate reference of
1.2V from the bandgap reference. The OVP threshold is set
by the resistive divider consisting of R1 and R2. The
protection threshold is set to 6.8V. When the input voltage
FN9280.2
June 30, 2008
ISL9212
exceeds the threshold, the CP1 outputs a logic signal to turn
off the power PFET within 1µs (see Figure 3) to prevent the
high input voltage from damaging the electronics in the
handheld system. The hysteresis for the input OVP
threshold is given in the “Electrical Specifications” table on
page 2. When the input overvoltage condition is removed,
the ISL9212 re-enables the output by running through the
soft-start, as shown in Figure 5. Because of the 10ms delay
before the soft-start, the output is never enabled if the input
rises above the OVP threshold quickly, as shown in Figure 6.
the enable pin is toggled. Figures 8 and 9 illustrate the
waveforms during the power-up when the output is
short-circuited to ground.
Battery Overvoltage Protection
External Enable Control
The battery voltage OVP is realized with the VB pin. The
comparator CP3, as shown in Figure 1, monitors the VB pin
and issues an overvoltage signal when the battery voltage
exceeds the 4.4V battery OVP threshold. The threshold has
75mV 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 PFET is turned off. The control
logic contains a 4-bit binary counter that if the battery
overvoltage event occurs 16 times, the power PFET is
turned off permanently, as shown in Figure 7. Recycling the
input power or toggling the enable (EN) input will reset the
counter and restart the ISL9212.
The ISL9212 offers an enable (EN) input. When the EN pin
is pulled to logic HIGH, the protection IC is shut down. The
internal control circuit as well as the power PFET are turned
off. Both 4-bit binary counters for the battery OVP and the
OCP are reset to zero when the IC is re-enabled. The EN pin
has an internal 200kΩ pull-down resistor. Leaving the EN pin
floating or driving it to below 0.4V enables the IC.
The resistor between the VB pin and the battery (RVB) as
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.
Applications Information
Overcurrent Protection (OCP)
The current in the power PFET 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 FET is
turned on. The reference of the OCP is generated using a
sensing FET (Q2), as shown in Figure 1. The current in the
sensing FET is forced to the value programmed by the ILIM
pin. The size of the power FET (Q1) is 31,250 times the size
of 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.
The OCP threshold can be calculated using Equation 1:
0.8V
25000
I LIM = --------------- ⋅ 31250 = ---------------R ILIM
R ILIM
(EQ. 1)
where the 0.8V is the regulated voltage at the ILIM pin. The
OCP comparator CP2 has a built-in 170µs 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 PFET is
turned off permanently unless the input power is recycled or
8
Internal Over-Temperature Protection
The ISL9212 monitors its own internal temperature to
prevent thermal failures. When the internal temperature
reaches +140°C, the IC turns off the P-Channel power
MOSFET. The IC does not resume operation until the
internal temperature drops below +90°C.
Warning Indication Output
The WRN pin is an open-drain output that indicates a LOW
signal when any of the three protection events happens. This
allows the microprocessor to give an indication to the user to
further enhance the safety of the charging system.
The ISL9212 is designed to meet the “Lithium-Safe” criteria
when operating together with the ISL6292 family Li-ion
battery chargers. The “Lithium-Safe” criteria requires the
charger output to fall within the green region shown in
Figure 23 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 have two
faults without creating hazardous conditions for the battery
cell. The output of any ISL6292 family chargers, 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 ISL9212 is to add an 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 ISL9212 and the ISL6292C chip set can easily
pass the “Lithium-Safe” criteria test procedures.
The ISL9212 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 RILIM is given in “Overcurrent Protection
(OCP)” on page 8.
FN9280.2
June 30, 2008
ISL9212
RVB Selection
The RVB prevents a large current from the VB pin to the
battery terminal, in case the ISL9212 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:
ISL9212
VIO
MCU
RPU
WRN
Q4
RWRN
( 30V – 4.2V ) ⁄ ( 200kΩ = 130μA )
(EQ. 2)
assuming the VB pin voltage is 30V 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 RVB value reduces the
worst case current, but at the same time increases the error
for the 4.4V 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 2 plus the voltage built across the RVB by the
VB pin leakage current. The VB pin leakage current is less
than 20nA, as given in the “Electrical Specifications” table.
With the 200kΩ resistor, the worst-case additional error is
4mV and with a 1MΩ resistor, the worst-case additional error
is 20mV.
1000
CHARGE CURRENT (mA)
ISL9212
LIMITS
ISL6292C
LIMITS
EN
Q5
REN
R5
FIGURE 24. DIGITAL SIGNAL INTERFACE BETWEEN ISL9212
AND MCU
Capacitor Selection
The input capacitor (C1 in the “Typical Application Circuit” on
page 1) is for decoupling. Higher value reduces the voltage
drop or the over shoot during transients.
Two scenarios can cause the input voltage over shoot. The
first one is when the AC adapter is inserted live (hot insertion)
and the second one is when the current in the power PFET of
the ISL9212 has a step-down change. Figure 25 shows an
equivalent circuit for the ISL9212 input. The cable between the
AC/DC converter output and the handheld system input has a
parasitic inductor. The parasitic resistor is the lumped sum of
various components, such as the cable, the adapter output
capacitor ESR, the connector contact resistance, and so on.
C1
L
R
AC/DC
0
1
2
3
4
5
ISL9212
6
BATTERY VOLTAGE (V)
FIGURE 23. LITHIUM-SAFE OPERATING REGIONS
Interfacing to MCU
The ISL9212 has the enable (EN) and the warning (WRN)
digital signals that can be interfaced to a microcontroller unit
(MCU). Both signals can be left floating if not used. When
interfacing to an MCU, it is highly recommended to insert a
resistor between the ISL9212 signal pin and the MCU GPIO
pin, as shown in Figure 24. The resistor creates an isolation
to limit the current, in case a high voltage shows up at the
ISL9212 pins under a failure mode. The recommended
resistance ranges from 10kΩ to 100kΩ. The selection of the
REN is dependent on the IO voltage (VIO) of the MCU. REN
should be selected so that the ISL9212 EN pin voltage is
above the disable threshold when the GPIO output of the
MCU is high.
9
C2
ADAPTER
CABLE
HANDHELD SYSTEM
FIGURE 25. EQUIVALENT CIRCUIT FOR THE ISL9212 INPUT
During the load current step-down transient, the energy
stored in the parasitic inductor is used to charge the input
decoupling capacitor C2. The ISL9212 is designed to turn off
the power PFET slowly during the OCP, the battery OVP
event, and when the device is disabled via the EN pin.
Because of such design, the input over shoot during those
events is not significant. During an input OVP, however, the
PFET is turned in less than 1µs and can lead to significant
over shoot. Higher capacitance reduces this type of over
shoot.
The over shoot caused by a hot insertion is not very
dependent on the decoupling capacitance value. Especially
when ceramic type capacitors are used for decoupling. In
theory, the over shoot can rise up to twice of the DC output
voltage of the AC adapter. The actual peak voltage is
FN9280.2
June 30, 2008
ISL9212
dependent on the damping factor that is mainly determined
by the parasitic resistance (R in Figure 25).
In practice, the input decoupling capacitor is recommended
to use a 16V X5R dielectric ceramic capacitor with a value
between 0.1µF to 1µF.
The output of the ISL9212 and the input of the charging
circuit typically share one decoupling capacitor. The
selection of that capacitor is mainly determined by the
requirement of the charging circuit. When using the ISL6292
family chargers, a 1µF, 6.3V, X5R capacitor is
recommended.
10
Layout Recommendation
The ISL9212 uses a thermally enhanced TDFN package.
The exposed pad under the package should be connected to
the ground plane electrically as well as thermally. A grid of
1.0mm to 1.2mm pitch thermal vias in two rows and 4 to 5
vias per row is recommended (refer to the ISL9212EVAL1Z
evaluation board layout). The vias should be about 0.3mm to
0.33mm in diameter. Use some copper on the component
layer if possible to further improve the thermal performance
but it is not mandatory.
Since the ISL9212 is a protection device, the layout should
also pay attention to the spacing between tracks. When the
distance between the edges of two tracks is less than
0.76mm, an FMEA (failure mechanism and effect analysis)
should be performed to ensure that a short between those
two tracks does not lead to the charger output exceeding the
“Lithium-Safe” region limits. Intersil will have the FMEA
document for the solution using the ISL9212 and the
ISL6292C chip set but the layout FMEA should be added as
part of the analysis.
FN9280.2
June 30, 2008
ISL9212
Thin Dual Flat No-Lead Plastic Package (TDFN)
L12.4x3A
2X
12 LEAD THIN DUAL FLAT NO-LEAD PLASTIC PACKAGE
(COMPLIANT TO JEDEC MO-229-WGED-4 ISSUE C)
0.15 C A
A
D
2X
MILLIMETERS
0.15 C B
SYMBOL
E
MIN
A
0.70
A1
-
A3
6
INDEX
AREA
b
D2
B
0.18
E2
A
SIDE VIEW
C
SEATING
PLANE
6
INDEX
AREA
C
0.08
C
A3
7
8
-
0.23
0.30
5,8
3.15
3.30
3.40
7,8
3.00 BSC
1.55
e
1.70
1.80
7,8
0.50 BSC
-
k
0.20
-
-
-
L
0.30
0.40
0.50
8
N
12
2
Nd
6
3
2. N is the number of terminals.
2
3. Nd refers to the number of terminals on D.
NX k
4. All dimensions are in millimeters. Angles are in degrees.
E2
5. Dimension b applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
E2/2
6. The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 identifier may be
either a mold or mark feature.
NX L
N
N-1
7. Dimensions D2 and E2 are for the exposed pads which provide
improved electrical and thermal performance.
NX b
e
5
(Nd-1)Xe
REF.
BOTTOM VIEW
NX (b)
0.05
1. Dimensioning and tolerancing conform to ASME Y14.5-1994.
(DATUM A)
8
-
NOTES:
D2/2
1
-
Rev. 0 1/06
D2
(DATUM B)
0.10
NOTES
0.80
4.00 BSC
E
//
MAX
0.75
0.20 REF
D
TOP VIEW
NOMINAL
0.10
8. Nominal dimensions are provided to assist with PCB Land
Pattern Design efforts, see Intersil Technical Brief TB389.
M C A B
CL
(A1)
L
5
e
SECTION "C-C" TERMINAL TIP
FOR EVEN TERMINAL/SIDE
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
11
FN9280.2
June 30, 2008