Product Preview
MC33345
LITHIUM BATTERY
PROTECTION CIRCUIT
FOR
ONE TO FOUR CELL
SMART BATTERY PACKS
SEMICONDUCTOR
TECHNICAL DATA
Lithium Battery Protection
Circuit for One to Four Cell
Battery Packs
The MC33345 is a monolithic lithium battery protection circuit that is
designed to enhance the useful operating life of one to four cell rechargeable
battery packs. Cell protection features consist of independently
programmable charge and discharge limits for both voltage and current with
a delayed current shutdown, cell voltage balancing with on–chip balancing
resistors, and a virtually zero current sleepmode state when the cells are
discharged. Additional features include an on–chip charge pump for reduced
MOSFET losses while charging or discharging a low cell voltage battery
pack, and the programmability for a one to four cell battery pack. This
protection circuit requires a minimum number of external components and is
targeted for inclusion within the battery pack. The MC33345 is available in
standard and low profile 20 lead surface mount packages.
•
Independently Programmable Charge and Discharge Limits for Both
Voltage and Current
•
Charge and Discharge Current Limit Detection with Delayed Shutdown
20
1
DW SUFFIX
PLASTIC PACKAGE
CASE 751D
(SO–20L)
•
•
•
•
•
•
•
Cell Voltage Balancing
On–Chip Balancing Resistors
Virtually Zero Current Sleepmode State when Cells are Discharged
Charge Pump for Reduced Losses with a Low Cell Voltage Battery Pack
Programmable for One, Two, Three or Four Cell Applications
Minimum External Components for Inclusion within the Battery Pack
Available in Low Profile Surface Mount Packages
PIN CONNECTIONS
Typical Four Cell Smart Battery Pack
Cell Voltage Return 1
Cell 4/VCC/
Discharge
Current Limit
2
Cell 3
20
Cell 2
19
Cell 1/VC
18
Ground
16
Program 1
11
Program 2
10
Charge Pump
Output
14 Discharge 13
Gate Drive
Output
Charge 9
Gate Drive
Output
8
Cell Voltage
3
Discharge Voltage
Threshold
4
Charge Voltage
Threshold
5
Cell Voltage
Return
1
Test Input
15
Fault Output
17
Charge
Gate Drive
Common
Current Sense
Common
Charge
Current Limit
20
1
DTB SUFFIX
PLASTIC PACKAGE
CASE 948E
(TSSOP–20)
20 Cell 3
19 Cell 2
18 Cell 1/VC
17 Fault Output
16 Ground
15 Test Input
14 Charge Pump Output
13 Discharge
Gate Drive Output
12 No Connection
11 Program 1
(Top View)
6
7
Cell 4/VCC/ 2
Discharge Current Limit
Cell Voltage 3
Discharge Voltage
Threshold 4
Charge Voltage 5
Threshold
Current Sense 6
Common
Charge Current Limit 7
Charge 8
Gate Drive Common
Charge 9
Gate Drive Output
Program 2 10
MC33345
ORDERING INFORMATION
Device
MC33345DW
Operating
Temperature Range
TA = –25° to +85°C
Package
SO–20L
TSSOP–20
This device contains 1808 active transistors.
MC33345DTB
3–316
MOTOROLA ANALOG IC DEVICE DATA
MC33345
MAXIMUM RATINGS
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Input Voltage (Measured with Respect to Ground, Pin 16)
Cell Voltage Divider (Pins 1, 3, 4 and 5)
Cell 1/VC (Pin 18)
Cell 2 (Pin 19)
Cell 3 (Pin 20)
Cell 4/VCC/Discharge Current Limit (Pin 2)
Current Sense Common (Pin 6)
Charge Current Limit (Pin 7)
Charge Gate Drive Common (Pin 8)
Charge Gate Drive Output (Pin 9)
Program 1 (Pin 11)
Program 2 (Pin 10)
Discharge Gate Drive Output (Pin 13)
Charge Pump Output (Pin 14)
Test (Pin 15)
Fault Output (Pin 17)
Cell Voltage Divider Current
Source Current (Pin 4 to 6)
Sink Current (Pin 5 to 16)
VIR
V
18
7.5
10
18
20
30
30
±20
18 to –20
7.5
7.5
18
12
7.5
20
0.5
0.5
10
Idiv
mA
Fault Output Sink Current (Pin 17)
Iflt
mA
Thermal Resistance, Junction to Air
DTB Suffix, TSSOP–20 Plastic Package, Case 948E
DW Suffix, SO–20 Plastic Package, Case 751D
Operating Junction Temperature (Notes 1, 2 and 3)
Storage Temperature
R
θJA
°C/W
135
105
TJ
–40 to +150
–55 to +150
°C
°C
Tstg
NOTE:
ESD data available upon request.
Ratings
Symbol
Value
Unit
ELECTRICAL CHARACTERISTICS
(VCC (Pin 2) = 8.0 V, VC (Pin 18) = 4.0 V, TA = 25°C, for min/max values TA is the
operating junction temperature range that applies (Notes 2 and 3), unless otherwise noted.)
Characteristic
VOLTAGE SENSING
Charge or Discharge Voltage Inputs (Pin 4 or 5 to Pin 1)
Threshold Voltage
Input Bias Current
Input Hysteresis Source Current (Pin 5)
Vth
IIB
–
–
–
–
–
–
–
–
1.23
20
2.0
–
–
–
–
–
–
–
–
V
nA
Symbol
Min
Typ
Max
Unit
IH
µA
V
Cell Charge or Discharge Programmable Input Voltage Range (Pin 4 or 5)
Cell Selector Series Resistance
Cell Positive to Top of Divider (Pin 2, 20, 19, or 18 to Pin 3)
Cell Negative to Bottom of Divider (Pin 20, 19, 18 or 16 to Pin 1)
Cell Voltage Sampling Rate
VIR(pgm)
RS+
RS–
Vth
Vth to 7.5
100
100
1.0
Ω
t(smpl)
s
Test Input Threshold Voltage (Pin 15)
VCell 1/2.0
V
CELL VOLTAGE BALANCING
Internal Balancing Resistance (Pins 2, 20, 19 and 18)
Rbal
–
140
–
Ω
CURRENT SENSING
Charge Current Limit (Pin 7 to Pin 6)
Threshold Voltage
Input Bias Current
Delay
Vth(chg)
IIB(chg)
Idly(chg)
–
–
–
18
200
1.0
–
–
–
mV
nA
s
NOTES:
1. Maximum package power dissipation limits must be observed.
2. Low duty cycle pulse techniques are used during test to maintain the junction temperature as close to ambient as possible.
3. Tested ambient temperature range for the MC33345:
Tlow = –25°C
Thigh = +85°C
MOTOROLA ANALOG IC DEVICE DATA
3–317
MC33345
ELECTRICAL CHARACTERISTICS
(continued)
(VCC (Pin 2) = 8.0 V, VC (Pin 18) = 4.0 V, TA = 25°C, for min/max values TA is the
operating junction temperature range that applies (Notes 2 and 3), unless otherwise noted.)
Characteristic
CURRENT SENSING
Symbol
Min
Typ
Max
Unit
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Discharge Current Limit (Pin 2 to Pin 6)
Threshold Voltage
Input Bias Current
Delay
Output Voltage (Pin 14, RL
≥
1010
Ω)
Vth(dschg)
IIB(dschg)
Idly(dschg)
VO
–
–
–
50
200
3.0
–
–
–
mV
nA
ms
CHARGE PUMP
–
10.2
–
V
TOTAL DEVICE
Average Cell Current
Operating (VCC = 8.0 V)
Sleepmode (VCC = 5.0 V)
ICC
–
–
15
5.0
–
–
µA
nA
V
Minimum Operating Cell Voltage for Logic and Gate Drivers
Programmed for One Cell Operation
Cell 1 Voltage
Programmed for Two, Three, or Four Cell Operation
Cell 1 Voltage
Cell 2, Cell 3, or Cell 4 Voltage, Sum Voltage of Cells
VCC
–
–
–
2.2
1.5
0.7
–
–
–
NOTES:
1. Maximum package power dissipation limits must be observed.
2. Low duty cycle pulse techniques are used during test to maintain the junction temperature as close to ambient as possible.
3. Tested ambient temperature range for the MC33345:
Tlow = –25°C
Thigh = +85°C
3–318
MOTOROLA ANALOG IC DEVICE DATA
MC33345
PIN FUNCTION DESCRIPTION
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1
2
Cell Voltage Return
The bottom side of a three resistor divider string connects to this pin. The Cell Selector internally
switches this point to the negative terminal of the cell that is to be monitored.
Cell 4/VCC/
Discharge Current Limit
This is a multifunction pin that connects to a high impedance node of the Cell Selector where it is used to
monitor the positive terminal of Cell 4 and to provide positive supply voltage for the protection IC. This pin
is also used to monitor the voltage drop across the discharge current limit resistor and it provides a
discharge path for the internal balancing of Cell 4.
The top side of a three resistor divider string connects to this pin. The Cell Selector internally switches
this point to the positive terminal of the cell that is to be monitored.
3
4
Cell Voltage
Discharge Voltage
Threshold
The upper tap of a three resistor divider string connects to this pin. The Cell Voltage Detector compares
the divided down cell voltage to an internal reference. If the comparator detects that the cell voltage has
fallen below the programmed level, discharge switch Q2 is disabled, and the protection circuit enters into
a low current sleepmode state. This prevents further discharging of the battery pack.
The lower tap of a three resistor divider string connects to this pin. The Cell Voltage Detector compares
the divided down cell voltage to an internal reference. If the comparator detects that the cell voltage has
risen above the programmed level, charge switch Q1 is disabled, preventing further charging of the
battery pack. A 2.0
µA
current source pull–up is internally applied to this pin creating input hysteresis.
This pin is a common point that is used to monitor the voltage drop across the charge and discharge
current limit resistors.
This pin is used to monitor the voltage drop across the charge current limit resistor.
5
Charge Voltage
Threshold
6
7
8
9
Current Sense Common
Charge Current Limit
Charge Gate Drive
Common
Charge Gate Drive
Output
Program 2
Program 1
This pin provides a gate turn–off path for charge switch Q1. The charge switch source and the battery
pack negative terminal connect to this point.
This output connects to the gate of charge switch Q1 allowing it to enable or disable battery pack
charging.
This pin is used in conjunction with Pin 11 to program the number of cells.
10
11
This pin is used in conjunction with Pin 10 to program the number of cells.
This pin is not internally connected.
12
13
14
15
16
17
18
No Connection
Discharge Gate Drive
Output
Charge Pump Output
Test Input
Ground
This output connects to the gate of discharge switch Q2 allowing it to enable or disable battery pack
discharging.
This is the charge pump output. A reservoir capacitor is connected from this pin to ground.
This input is used to facilitate circuit testing and is normally not connected. It has an internal 2.0 k pull–up
resistor.
This is the protection IC ground and all voltage ratings are with respect to this pin.
Fault Output
Cell 1/VC
This is on open drain output that is active low when a charging fault limit has been exceeded. The limits
sensed are both charge voltage and current.
This is a multifunction pin that connects to a high impedance node of the Cell Selector where it is used to
monitor the positive terminal of Cell 1 and the negative terminal of Cell 2. This pin also provides logic
biasing and a discharge path for the internal balancing of Cell 1.
This pin connects to a high impedance node of the Cell Selector where it is used to monitor the positive
terminal of Cell 2 and the negative terminal of Cell 3. This pin also provides a discharge path for the
internal balancing of Cell 2.
This pin connects to a high impedance node of the Cell Selector where it is used to monitor the positive
terminal of Cell 3 and the negative terminal of Cell 4. This pin also provides a discharge path for the
internal balancing of Cell 3.
19
Cell 2
20
Cell 3
Pin
Symbol
Description
MOTOROLA ANALOG IC DEVICE DATA
3–319
MC33345
INTRODUCTION
The insatiable demand for smaller lightweight portable
electronic equipment has dramatically increased the
requirements of battery performance. Batteries are expected
to have higher energy densities, superior cycle life, be safe in
operation and environmentally friendly. To address these high
expectations, battery manufacturers have invested heavily in
developing rechargeable lithium–based cells. Today’s most
attractive chemistries include lithium–polymer, lithium–ion,
and lithium–metal. Each of these chemistries require
electronic protection in order to constrain cell operation to
within the manufacturers limits.
Rechargeable lithium–based cells require precise charge
and discharge termination limits for both voltage and current
in order to maximize cell capacity, cycle life, and to protect
the end user from a catastrophic event. The termination limits
are not as well defined as with older non–lithium chemistries.
These limits are dependent upon a manufacturer’s particular
lithium chemistry, construction technique, and intended
application. Battery pack assemblers may also choose to
enhance cell capacity at the expense of cycle life. In order to
address these requirements the MC33345 was developed.
This device features programmable voltage and current
limits, cell voltage balancing, low operating current, a virtually
zero current sleepmode state, and requires few external
components to implement a complete one to four cell smart
battery pack.
This configuration allows the protection circuit to interrupt
the appropriate charge or discharge path FET in the event
that a programmed voltage or current limit for any cell has
been exceeded.
A functional description of the protection circuit blocks
follows. Refer to the detailed block diagram shown in
Figure 6.
Voltage Sensing
Individual cell voltage sensing is accomplished by the use
of the Cell Selector in conjunction with the Floating
Over/Under Voltage Detector and Reference block. The Cell
Selector applies the voltage of each cell across an external
resistor divider string that connects from Pins 3 to 1. The
voltage at each of the tap points is sequentially polled and
compared to an internal reference. If a limit has been
exceeded, the result is stored in the Over/Under Data Latch
and Control Logic block. The Cell Selector is gated on for an
8.0 ms period at a one second repetition rate. This low duty
cycle sampling technique reduces the average load current
that the divider presents across each cell, thus extending the
useful battery pack capacity. The cells are sensed in the
following sequence:
Figure 2. Cell Sensing Sequence
Polling
Sequence
1
2
3
4
5
6
7
8
Time
(ms)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Cell
Sensed
Cell 4
Cell 3
Cell 2
Cell 1
Cell 4
Cell 3
Cell 2
Cell 1
Tested
Limit
Overvoltage
Overvoltage
Overvoltage
Overvoltage
OPERATING DESCRIPTION
The MC33345 is specifically designed to be placed in the
battery pack where it is continuously powered from either one,
two, three, or four lithium cells. In order to maintain cell
operation within specified limits, the protection circuit senses
both cell voltage and current, and correspondingly controls the
state of two N–channel MOSFET switches. These switches,
Q1 and Q2, are placed in series with the negative terminal of
Cell 1 and the negative terminal of the battery pack.
Figure 1. Simplified Four Cell Smart Battery Pack
RLim(dschg)
6
Cell 4
RLim(chg)
7
2
3
Cell 3
20
4
R1
R2
Cell 2
19
MC33345
18
5
R3
Cell 1
1
16
11
10
17
14
13
9
8
15
Discharge
MOSFET Q2
Charge
MOSFET Q1
3–320
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Undervoltage
Undervoltage
Undervoltage
Undervoltage
By incorporating this polling technique with a single
floating comparator and voltage divider, a significant
reduction of circuitry and trim elements is achieved. This
results in a smaller die size, lower cost, and reduced
operating current.
Figure 3. Cell Voltage Limit Programming
From
Cell
Selector
Floating
Over/Under
Cell Voltage
Detector
&
Reference
To
Cell
Selector
Cell Voltage
3
Discharge Voltage
Threshold
4
Charge Voltage
Threshold
5
Cell Voltage
Return
1
R1
+
Cell
Voltage
R2
–
R3
The cell charge and discharge voltage limits are controlled
by the values selected for the resistor divider string and the
1.23 V input threshold of Pins 4 and 5. As the battery pack
reaches full charge, the Cell Voltage Detector will sense an
overvoltage fault condition on the first cell that exceeds the
programmed overvoltage limit. The fault information is stored
MOTOROLA ANALOG IC DEVICE DATA
Embedded System
京公网安备 11010802033920号
EEWORLD
