LTC1325
Microprocessor-Controlled
Battery Management System
FEATURES
s
s
DESCRIPTION
The LTC
®
1325 provides the core of a flexible, cost-effec-
tive solution for an integrated battery management sys-
tem. The monolithic CMOS chip controls the fast charging
of nickel-cadmium, nickel-metal-hydride, lead-acid or
lithium batteries under microprocessor control. The de-
vice features a programmable 111kHz PWM constant
current source controller with built-in FET driver, 10-bit
ADC, internal voltage regulator, discharge-before-charge
controller, programmable battery voltage attenuator and
an easy-to-use serial interface.
The chip may operate in one of five modes: power shut-
down, idle, discharge, charge or gas gauge. In power
shutdown the supply current drops to 30µA and in the idle
mode, an ADC reading may be made without any switching
noise affecting the accuracy of the measurement. In the
discharge mode, the battery is discharged by an external
transistor while the battery is being monitored by the
LTC1325 for fault conditions. The charge mode is termi-
nated by the
µP
while monitoring any combination of
battery voltage and temperature, ambient temperature
and charge time. The LTC1325 also monitors the battery
for fault conditions before and during charging. In the gas
gauge mode the LTC1325 allows the total charge leaving
the battery to be calculated.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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s
s
s
s
s
s
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Fast Charge Nickel-Cadmium, Nickel-Metal-Hydride,
Lithium Ion or Lead-Acid Batteries under
µ
P Control
Flexible Current Regulation:
– Programmable 111kHz PWM Current Regulator
with Built-In PFET Driver
– PFET Current Gating for Use with External Current
Regulator or Current Limited Transformer
Discharge Mode
Measures Battery Voltage, Battery Temperature and
Ambient Temperature with Internal 10-Bit ADC
Battery Voltage, Temperature and Charge Time
Fault Protection
Built-In Voltage Regulator and Programmable
Battery Attenuator
Easy-to-Use 3- or 4-Wire Serial
µ
P Interface
Accurate Gas Gauge Function
Wide Supply Range: V
DD
= 4.5V to 16V
Can Charge Batteries with Voltages Greater Than V
DD
Can Charge Batteries from Charging Supplies Greater
Than V
DD
Digital Input Pins Are High Impedance in
Shutdown Mode
APPLICATIONS
s
System Integrated Battery Charger
TYPICAL APPLICATION
Battery Charger for up to 8 NiCd or NiMH Cells
+
C2
10µF
P1
IRF9730
D1
1N6818
LTC1325
MPU
(e.g. 8051)
p1.4
p1.3
p1.2
R1
+
C
REG
4.7µF
1
2
3
4
5
6
7
REG
D
OUT
D
IN
CS
CLK
LTF
MCV
HTF
GND
V
DD
PGATE
DIS
V
BAT
T
BAT
T
AMB
V
IN
SENSE
FILTER
18
17
16
15
14
13
12
11
10
C
F
1µF
100Ω
R13
R5
+
C1
0.1µF
C
REG
22µF
THERM 2
THERM 1
R2
8
9
R3
R4
U
U
U
V
DD
4.5V TO 16V
L1
62µH
R
TRK
R
DIS
BAT
N1
IRFZ34
R
SENSE
LTC1325 • TA01
1
LTC1325
ABSOLUTE
MAXIMUM
RATINGS
(Notes 1, 2)
PACKAGE/ORDER INFORMATION
TOP VIEW
REG 1
D
OUT
2
D
IN
3
CS 4
CLK 5
LTF 6
MCV 7
HTF 8
GND 9
N PACKAGE
18-LEAD PDIP
18 V
DD
17 PGATE
16 DIS
15 V
BAT
14 T
BAT
13 T
AMB
12 V
IN
11 SENSE
10 FILTER
SW PACKAGE
18-LEAD PLASTIC SO WIDE
V
DD
to GND ............................................................. 17V
All Other Pins ................................ – 0.3V to V
DD
+ 0.3V
Operating Temperature Range ..................... 0°C to 70°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1325CN
LTC1325CSW
T
JMAX
= 125°C,
θ
JA
= 75°C/ W (N)
T
JMAX
= 125°C,
θ
JA
= 100°C/ W (SW)
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
DD
I
DD
I
PD
V
REG
LD
REG
LI
REG
TC
REG
V
DAC
PARAMETER
V
DD
Supply Voltage
V
DD
Supply Current
V
DD
Supply Current
Regulator Output Voltage
Regulator Load Regulation
Regulator Line Regulation
Regulator Output Tempco
DAC Output Voltage
CONDITIONS
V
DD
= 12V
±5%,
T
A
= 25°C, unless otherwise noted.
q
MIN
4.5
TYP
1200
30
3.072
–1
– 60
50
160
55
34
18
±20
±10
±50
100
V
HYST
V
OS
V
BATR
V
BATP
V
EDV
V
LTF
, V
MCV
V
HTF
A
GG
V
OS(GG)
R
F
TOL
BATD
V
IL
V
IH
I
IL
I
IH
Fault Comparator Hysteresis
Fault Comparator Offset
V
BAT
for BATR = 1
V
BAT
for BATP = 1
Internal EDV Voltage
LTF, MCV Voltage Range
HTF Voltage Range
Gas Gauge Gain
Gas Gauge Offset
Internal Filter Resistor
Battery Divider Tolerance
Input Low Voltage
Input High Voltage
Low Level Input Current
High Level Input Current
All TTL Inputs = 0V or 5V, No Load on REG
Power-Down Mode, All TTL Inputs = 0V or 5V
No Load
Sourcing Only, I
REG
= 0mA to 2mA
No Load, V
DD
= 4.5V to 16V
No Load, 0°C < T
A
< 70°C
VR1 = 1, VR0 = 1, 100% Duty Ratio, I
CHRG
= I (Note 7)
VR1 = 1, VR0 = 0, 100% Duty Ratio, I
CHRG
= I/3
VR1 = 0, VR0 = 1, 100% Duty Ratio, I
CHRG
= I/5
VR1 = 0, VR0 = 0, 100% Duty Ratio, I
CHRG
= I/10
V
HTF
= 1V, V
EDV
= 0.9V, V
BATR
= 100mV
V
MCV
= V
LTF
= 2V
V
HTF
= 1V, V
EDV
= 0.9V, V
BATR
= 100mV
V
MCV
= V
LTF
= 2V
q
q
q
3.047
MAX
16
2000
50
3.097
–5
– 100
180
62
38
21
140
48
30
16
UNITS
V
µA
µA
V
mV/mA
µV/V
ppm/°C
mV
mV
mV
mV
mV
mV
mV
mV
V
mV
V
V
LSB
Ω
%
V
V
µA
µA
q
q
V
DD
– 1.8
860
1.6
0.5
900
945
2.8
1.3
– 0.4V < V
SENSE
< 0V
– 0.4V < V
SENSE
< 0V (Note 6)
All Division Ratios
CLK, CS, D
IN
CLK, CS, D
IN
V
CLK
, V
CS
or V
DIN
= 0V
V
CLK
, V
CS
or V
DIN
= 5V
q
q
q
q
q
–4
±1
1000
–2
0.8
– 2.5
– 2.5
2
1.3
1.7
2.4
2.5
2.5
2
U
W
U
U
W W
W
LTC1325
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
V
OL
Output Low Voltage
V
OH
Output High Voltage
I
OZ
Hi-Z Output Leakage
V
OHFET
DIS or PGATE Output High
V
OLFET
DIS or PGATE Output Low
t
dDO
Delay Time, CLK↓ to D
OUT
Valid
t
dis
Delay Time, CS↑ to D
OUT
Hi-Z
t
en
Delay Time, CLK↓ to D
OUT
Enabled
t
hDO
Time D
OUT
Remains Valid After CLK↓
t
rDOUT
D
OUT
Rise Time
t
fDOUT
D
OUT
Fall Time
f
CLK
Serial I/O Clock Frequency
t
rPGATE
PGATE Rise Time
t
fPGATE
PGATE Fall Time
f
OSC
Internal Oscillator Frequency
A/D Converter
Offset Error
Linearity Error
Full-Scale Error
On-Channel Leakage
Off-Channel Leakage
V
DD
= 12V
±5%,
T
A
= 25°C, unless otherwise noted.
MIN
q
q
q
q
q
q
q
q
q
q
q
q
q
q
CONDITIONS
D
OUT
, I
OUT
= 1.6mA
D
OUT
, I
OUT
= – 1.6mA
V
CS
= 5V
V
DD
= 4.5V to 16V
V
DD
= 4.5V to 16V
See Test Circuits
See Test Circuits
See Test Circuits
See Test Circuits
See Test Circuits
See Test Circuits
CLK Pin
C
LOAD
= 1500pF
C
LOAD
= 1500pF
Charge Mode, Fail-Safes Disabled
V
IN
Channel (Note 3)
V
IN
Channel (Notes 3, 4)
V
IN
Channel (Note 3)
V
IN
Channel ON Only (Notes 3, 5)
V
IN
Channel OFF (Notes 3, 5)
TYP
MAX
0.4
±10
2.4
V
DD
– 0.05
0.05
650
510
400
30
250
100
500
150
150
130
±2
±0.5
±1
±10
±10
25
90
q
q
q
q
q
111
UNITS
V
V
µA
V
V
ns
ns
ns
ns
ns
ns
kHz
ns
ns
kHz
LSB
LSB
LSB
µA
µA
RECO
SYMBOL
t
hDI
t
dsuCS
t
dsuDI
t
WHCLK
t
WLCLK
t
WHCS
t
WLCS
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All voltage values are with respect to the GND pin.
Note 3:
V
REG
within specified min and max limits, CLK (Pin 5) = 500kHz,
unless otherwise stated. ADC clock is the serial CLK.
U WW
E DED CHARACTERISTICS
CONDITIONS
MIN
150
1
400
0.8
1
1
43
52
TYP
MAX
UNITS
ns
µs
ns
µs
µs
µs
CLK Cycles
CLK Cycles
PARAMETER
Hold Time, D
IN
After CLK↑
Setup Time, CS Before First CLK↑
Setup Time, D
IN
Stable Before First CLK↑
CLK High Time
CLK Low Time
CS High Time Between Data Transfers
CS Low Time During Data Transfer
MSBF = 1
MSBF = 0
Note 4:
Linearity error is specified between the actual end points of the
A/D transfer curve.
Note 5:
Channel leakage is measured after channel selection.
Note 6:
Gas gauge offset excludes A/D offset error.
Note 7:
I = V
DAC
(Duty Ratio)/R
SENSE
, where V
DAC
is the DAC output
voltage with control bits VR1 = VR0 = 1, duty ratio = 1 and R
SENSE
is
determined by the user.
3
LTC1325
TYPICAL PERFORMANCE CHARACTERISTICS
Regulator Output Voltage vs
Load Current
3.077
T
A
= 27°C
REGULATOR OUTPUT VOLTAGE (V)
3.076
3.075
3.074
V
DD
= 12V
V
DD
= 4.5V
3.079
3.078
3.077
3.076
3.075
3.074
3.073
3.072
0
10
V
DD
= 16V
V
DD
= 12V
VDD SUPPLY CURRENT (µA)
V
DD
= 16V
REGULATOR OUTPUT VOLTAGE (V)
3.073
3.072
3.071
3.070
0
0.5
1.0
3.0 3.5
LOAD CURRENT (mA)
1.5
2.0
2.5
4.0
Charge Current vs Battery Voltage
160
VR1 = 1, VR0 = 1
140
DAC OUTPUT VOLTAGE (mV)
CHARGE CURRENT (mA)
120
100
80
60
40
20
0
0
V
DD
= 12V, R
SENSE
= 1Ω,
L = 100µH, P1: IRF9531
120
100
80
60
40
20
0
VR1 = 1, VR0 = 0
VR1 = 0, VR0 = 1
VR1 = 0, VR0 = 0
0
10
40
30
50
20
TEMPERATURE (°C)
60
70
V
DD
= 12V
SHUTDOWN CURRENT (µA)
VR1 = 1, VR0 = 0
VR1 = 0, VR0 = 1
VR1 = 0, VR0 = 0
2
4
6
8
BATTERY VOLTAGE (V)
10
12
1325 G04
Fault Comparator Threshold vs
Temperature
1.0
FAULT COMPARATOR THRESHOLD (V)
FAULT COMPARATOR THRESHOLD (V)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
10
V
CELL
FOR EDV = HIGH
10
9
8
7
6
5
4
3
2
1
0
V
BAT
FOR BATP = HIGH, V
DD
= 12V
GAS GAUGE GAIN AND OFFSET (COUNTS)
V
TBAT
FOR HTF = HIGH, V
HTF
= 0.4V
V
CELL
FOR BATR = HIGH
20
30 40 50 60
TEMPERATURE (°C)
4
U W
70
1325 G07
Regulator Output Voltage vs
Temperature
3.082
3.081
3.080
I
REG
= 0
1000
900
800
700
600
500
400
300
200
100
20
30 40 50 60 70
TEMPERATURE (°C)
80
90
0
V
DD
Supply Current vs
Temperature
V
DD
= 16V
V
DD
= 4.5V
V
DD
= 12V
V
DD
= 4.5V
0
10
20
30 40 50 60 70
TEMPERATURE (°C)
80
90
1325 G01
1325 G02
1325 G03
DAC Output Voltage vs
Temperature
180
160
140
VR1 = 1, VR0 = 1
20
25
Shutdown Current vs Temperature
V
DD
= 16V
15
V
DD
= 12V
10
5
V
DD
= 4.5V
0
0
10
20
30 40 50 60 70
TEMPERATURE (°C)
80
90
1325 G05
1325 G06
Fault Comparator Threshold vs
Temperature
11
Gas Gauge Gain and Offset vs
Temperature
0
– 0.5
–1.0
–1.5
–2.0
–2.5
–3.0
– 3.5
GAS GAUGE GAIN
–4.0
–4.5
0
10
20
30 40 50 60
TEMPERATURE (°C)
70
80
GAS GAUGE OFFSET
V
SENSE
= –0.2V AND – 0.4V
INCLUDES CHANGES IN V
REG
WITH TEMPERATURE
V
CELL
FOR MCV = HIGH, V
MCV
= 2.8V AND
V
TBAT
FOR LTF = HIGH, V
LTF
= 2.8V
V
CELL
FOR MCV = HIGH, V
MCV
= 1.6V
V
TBAT
FOR LTF = HIGH, V
LTF
= 1.6V
V
TBAT
FOR HTF = HIGH, V
HTF
= 1.35V
70
80
10
20
30 40 50 60
TEMPERATURE (°C)
80
1325 G08
1325 G09
LTC1325
TYPICAL PERFORMANCE CHARACTERISTICS
PGATE Rise Time vs
Load Capacitance
1200
1000
1000
DIFFERENTIAL NONLINEARITY (LSB)
PGATE RISE TIME (ns)
800
600
400
200
0
0
2
4
T
A
= 27°C
T
A
= 70°C
PGATE FALL TIME (ns)
T
A
= 0°C
6 8 10 12 14 16 18 20
LOAD CAPACITANCE (nF)
1325 G10
Discharge Rise and Fall Time
vs Load Capacitance
14
DISCHARGE RISE AND FALL TIME (µs)
MINIMUM CHARGE VOLTAGE (V)
RISE TIME
10
8
6
FALL TIME
4
2
0
0
2
4
6
8 10 12 14 16 18 20
LOAD CAPACITANCE (nF)
1325 G13
12
10
8
6
4
2
0
1
2
3
4
5
6
7
8
1325 G14
INTEGRAL NONLINEARITY (LSB)
12
T
A
= 70°C
T
A
= 27°C
T
A
= 0°C
Oscillator Frequency vs
Temperature
118
500
CLK TO D
OUT
ENABLE DELAY TIME (ns)
CLK TO D
OUT
VALID DELAY TIME (ns)
117
OSCILLATOR FREQUENCY (kHz)
116
115
114
113
112
111
110
109
108
–40 –20
40
20
0
60
TEMPERATURE (°C)
80
100
U W
1325 G16
PGATE Fall Time vs
Load Capacitance
1.0
Differential Nonlinearity
V
DD
= 12V
f
CLK
= 500kHz
0.5
900
800
700
600
500
400
300
200
100
0
0
2
4
6 8 10 12 14 16 18 20
LOAD CAPACITANCE (nF)
LTC1325 G11
T
A
= 27°C
T
A
= 70°C
0
T
A
= 0°C
–0.5
–1.0
0
128 256 384 512 640 768 896 1024
CODE
1325 G12
Minimum Charging Supply vs
Number of Cells
16
14
R
SENSE
= 0.15, VR1 = 1,VR0 = 1
L = 10µH TO 100µH
IRF9Z30PFET, 1N5819 DIODE
Integral Nonlinearity
1.0
V
DD
= 12V
f
CLK
= 500kHz
0.5
0
R
SENSE
= 1, VR1 = 1, VR0 = 1
L = 25µH TO 100µH
IRF9Z30PFET, 1N5819 DIODE
T
A
= 27°C, NiCd BATTERIES
V
CELL
= 1.4V NOMINAL
–0.5
–1.0
0
NUMBER OF CELLS
128 256 384 512 640 768 896 1024
CODE
1325 G15
CLK to D
OUT
Enable Delay Time
vs Temperature
700
600
500
400
300
200
100
0
0
10
20
30 40 50 60
TEMPERATURE (°C)
70
80
450
400
350
300
250
200
150
100
50
0
CLK to D
OUT
Valid Delay Time
vs Temperature
D
OUT
GOING HIGH
D
OUT
GOING LOW
0
10
20
30
40
50
60
70
80
TEMPERATURE (°C)
1325 G17
1325 G18
5
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