UC2906
UC3906
Sealed Lead-Acid Battery Charger
FEATURES
Optimum Control for Maximum
Battery Capacity and Life
Internal State Logic Provides
Three Charge States
Precision Reference Tracks
Battery Requirements Over
Temperature
Controls Both Voltage and
Current at Charger Output
System Interface Functions
Typical Standby Supply
Current of only 1.6mA
DESCRIPTION
The UC2906 series of battery charger controllers contains all of the necessary
circuitry to optimally control the charge and hold cycle for sealed lead-acid batter-
ies. These integrated circuits monitor and control both the output voltage and cur-
rent of the charger through three separate charge states; a high current
bulk-charge state, a controlled over-charge, and a precision float-charge, or
standby, state.
Optimum charging conditions are maintained over an extended temperature
range with an internal reference that tracks the nominal temperature charac-
teristics of the lead-acid cell. A typical standby supply current requirement of only
1.6mA allows these ICs to predictably monitor ambient temperatures.
Separate voltage loop and current limit amplifiers regulate the output voltage and
current levels in the charger by controlling the onboard driver. The driver will sup-
ply up to 25mA of base drive to an external pass device. Voltage and current
sense comparators are used to sense the battery condition and respond with
logic inputs to the charge state logic. A charge enable comparator with a trickle
bias output can be used to implement a low current turn-on mode of the charger,
preventing high current charging during abnormal conditions such as a shorted
battery cell.
Other features include a supply under-voltage sense circuit with a logic output to
indicate when input power is present. In addition the over-charge state of the
charger can be externally monitored and terminated using the over-charge indi-
cate output and over-charge terminate input.
BLOCK DIAGRAM
SLUS186 - SEPTEMBER 1996
CONNECTION DIAGRAMS
UC2906
UC3906
Supply Voltage (+V
IN
). . . . . . . . . . . . . . . . . . . . . . . . . . . 40V
Open Collector Output Voltages. . . . . . . . . . . . . . . . . . . 40V
Amplifier and Comparator Input Voltages . . . -0.3V to +40V
Over-Charge Terminate Input Voltage . . . . . . -0.3V to +40V
Current Sense Amplifier Output Current . . . . . . . . . . 80mA
Other Open Collector Output Currents. . . . . . . . . . . . 20mA
Trickle Bias Voltage Differential with respect to V
IN
. . . -32V
Trickle Bias Output Current . . . . . . . . . . . . . . . . . . . . -40mA
Driver Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80mA
Power Dissipation at T
A
= 25C(Note 2) . . . . . . . . 1000mW
Power Dissipation at T
C
= 25C (Note 2) . . . . . . . . 2000mW
Operating Junction Temperature . . . . . . . . -55C to +150C
Storage Temperature . . . . . . . . . . . . . . . . . -65C to +150C
Lead Temperature (Soldering, 10 Seconds) . . . . . . . 300C
Note 1: Voltages are referenced to ground (Pin 6). Currents
are positive into, negative out of, the specified terminals.
Note 2: Consult Packaging section of Databook for thermal
limitations and considerations of packages.
DIL-16, SOIC-16 (TOP VIEW)
J or N Package, DW Package
PACKAGE PIN FUNCTION
FUNCTION
PIN
N/C
1
C/S OUT
2
C/S-
3
C/S+
4
C/L
5
N/C
6
+V
IN
7
GROUND
8
POWER INDICATE
9
OVER CHARGE
TERMINATE
10
N/C
11
OVER CHARGE
INDICATE
12
STATE LEVEL
CONTROL
13
TRICKLE BIAS
14
CHARGE ENABLE
15
N/C
16
VOLTAGE SENSE
17
COMPENSATION
18
DRIVER SOURCE
19
DRIVER SINK
20
PLCC-20, LCC-20
(TOP VIEW)
Q, L Packages
ABSOLUTE MAXIMUM RATINGS (Note 1)
PARAMETER
TEST CONDITIONS
UC2906
UC3906
UNITS
MIN
TYP
MAX
MIN
TYP
MAX
Input Supply
Supply Current
+V
IN
= 10V
1.6
2.5
1.6
2.5
mA
+V
IN
= 40V
1.8
2.7
1.8
2.7
mA
Supply Under-Voltage Threshold +V
IN
= Low to High
4.2
4.5
4.8
4.2
4.5
4.8
V
Supply Under-Voltage Hysteresis
0.20
0.30
0.20
0.30
V
Internal Reference (V
REF
)
Voltage Level (Note 3)
Measured as Regulating Level at
Pin 13 w/ Driver Current = 1mA,
T
J
= 25C
2.275
2.3
2.325
2.270
2.3
2.330
V
Line Regulation
+V
IN
= 5 to 40V
3
8
3
8
mV
Temperature Coefficient
-3.9
-3.9
mV/C
Voltage Amplifier
Input Bias Current
Total Input Bias at Regulating Level
-0.5
-0.2
-0.5
-0.2
A
Maximum Output Current
Source
-45
-30
-15
-45
-30
-15
A
Sink
30
60
90
30
60
90
A
Open Loop Gain
Driver current = 1mA
50
65
50
65
dB
Output Voltage Swing
Volts above GND or below +V
IN
0.2
0.2
V
Unless otherwise stated, these specifications apply for T
A
= -40C to +70C for the
UC2906 and 0C to +70C for the UC3906, +V
IN
= 10V, T
A
= T
J.
ELECTRICAL CHARACTERISTICS:
Note 3. The reference voltage will change as a function of power dissipation on the die according to the temperature coefficient of
the reference and the thermal resistance, junction-to-ambient.
2
PARAMETER
TEST CONDITIONS
UC2906
UC3906
UNITS
MIN
TYP
MAX
MIN
TYP
MAX
Driver
Minimum Supply to Source
Differential
Pin 16 = +V
IN
, I
O
= 10mA
2.0
2.2
2.0
2.2
V
Maximum Output Current
Pin 16 to Pin 15 = 2V
25
40
25
40
mA
Saturation Voltage
0.2
0.45
0.2
0.45
V
Current Limit Amplifier
Input Bias Current
0.2
1.0
0.2
1.0
A
Threshold Voltage
Offset below +V
IN
225
250
275
225
250
275
mV
Threshold Supply Sensitivity
+V
IN
= 5 to 40V
0.03
0.25
0.03
0.25
%/V
Voltage Sense Comparator
Threshold Voltage
As a function of V
REF
, L
1
= RESET
0.945
0.95
0.955
0.945
0.95
0.955
V/V
As a function of V
REF
, L
1
= SET
0.895
0.90
0.905
0.895
0.90
0.905
V/V
Input Bias Current
Total Input Bias at Thresholds
-0.5
-0.2
-0.5
-0.2
A
Current Sense Comparator
Input Bias Current
0.1
0.5
0.1
0.5
A
Input Offset Current
0.01
0.2
0.01
0.2
A
Input Offset Voltage
Referenced to Pin 2, I
OUT
= 1mA
20
25
30
20
25
30
mV
Offset Supply Sensitivity
+V
IN
= 5 to 40V
0.05
0.35
0.05
0.35
%/V
Offset Common Mode Sensitivity CMV = 2V to +V
IN
0.05
0.35
0.05
0.35
%/V
Maximum Output Current
V
OUT
= 2V
25
40
25
40
mA
Output Saturation Voltage
I
OUT
= 10mA
0.2
0.45
0.2
0.45
V
Enable Comparator
Threshold Voltage
As a function of V
REF
0.99
1.0
1.01
0.99
1.0
1.01
V/V
Input Bias Current
-0.5
-0.2
-0.5
-0.2
A
Trickle Bias Maximum Output
Current
V
OUT
= +V
IN
-
3V
25
40
25
40
mA
Trickle Bias Maximum Output
Voltage
Volts below +V
IN,
I
OUT
= 10mA
2.0
2.6
2.0
2.6
V
Trickle Bias Reverse Hold-Off
Voltage
+V
IN
= 0V, I
OUT
= -10
A
6.3
7.0
6.3
7.0
V
Over-Charge Terminate Input
Threshold Voltage
0.7
1.0
1.3
0.7
1.0
1.3
V
Internal Pull-Up Current
At Threshold
10
10
A
Open Collector Outputs (Pins 7, 9, and 10)
Maximum Output Current
V
OUT
= 2V
2.5
5
2.5
5
mA
Saturation Voltage
I
OUT
= 1.6mA
0.25
0.45
0.25
0.45
V
I
OUT
= 50
A
0.03
0.05
0.03
0.05
V
Leakage Current
V
OUT
= 40V
1
3
1
3
A
ELECTRICAL CHARACTERISTICS:
Unless otherwise stated, these specifications apply for T
A
= -40C to +70C for the
UC2906 and 0C to +70C for the UC3906, +V
IN
= 10V, T
A
= T
J.
UC2906
UC3906
3
Dual Level Float Charger Operations
The UC2906 is shown configured as a dual level float
charger in Figure 1. All high currents are handled by the
external PNP pass transistor with the driver supplying
base drive to this device. This scheme uses the TRICKLE
BIAS output and the charge enable comparator to give
the charger a low current turn on mode. The output cur-
rent of the charger is limited to a low-level until the battery
reaches a specified voltage, preventing a high current
charging if a battery cell is shorted. Figure 2 shows the
state diagram of the charger. Upon turn on the UV sense
circuitry puts the charger in state 1, the high rate bulk-
charge state. In this state, once the enable threshold has
been exceeded, the charger will supply a peak current
that is determined by the 250mV offset in the C/L ampli-
fier and the sensing resistor R
S.
To guarantee full re-charge of the battery, the charger's
voltage loop has an elevated regulating level, V
OC
, during
state 1 and state 2. When the battery voltage reaches
95% of V
OC
, the charger enters the over-charge state,
state 2. The charger stays in this state until the OVER-
CHARGE TERMINATE pin goes high. In Figure 1, the
charger uses the current sense amplifier to generate this
signal by sensing when the charge current has tapered to
a specified level, I
OCT
. Alternatively the over-charge could
have been controlled by an external source, such as a
timer, by using the OVER-CHARGE INDICATE signal at
Pin 9. If a load is applied to the battery and begins to dis-
charge it, the charger will contribute its full output to the
load. If the battery drops 10% below the float level, the
charger will reset itself to state 1. When the load is re-
moved a full charge cycle will follow. A graphical repre-
sentation of a charge, and discharge, cycle of the dual
lever float charger is shown in Figure 3.
UC2906
UC3906
Figure 1.
The UC2906 in a Dual Level Float Charger
OPERATION AND APPLICATION INFORMATION
Internal Reference Temperature Characteristic and
Tolerance
4
Design procedure
1.) Pick divider current, I
D
. Recommended value is
50
A to 100
A.
2.)
R
C
=
2.3
V
/
I
D
3.)
R
A
+
R
B
=
R
SUM
=
(
V
F
-
2.3
V
)
/
I
D
4.)
R
D
=
2.3
VR
SUM
/
(
V
OC
-
V
F
)
5.)
R
A
=
(
R
SUM
+
R
X
)
(
1
-
2.3
V
/
V
T
)
where:
R
X
=
R
C
R
D
/
(
R
C
+
R
D
)
6.)
R
B
=
R
SUM
-
R
A
7.)
R
S
=
0.25
V
/
I
MAX
8.)
R
T
=
(
V
IN
-
V
T
-
2.5V
)
/
I
T
Note:V
12
=
0.95
V
OC
V
31
=
0.90
V
F
I
OCT
=
I
MAX
10
For further design and application information see
UICC Application Note U-104
Explanation: Dual Level Float Charger
A. Input power turns on, battery charges at trickle current rate.
B. Battery voltage reaches V
T
enabling the driver and turning
off the trickle bias output, battery charges at l
MAX
rate.
C. Transition voltage V
12
is reached and the charger indicates
that it is now in the over-charge state, state 2.
D. Battery voltage approaches the over-charge level V
OC
and
the charge current begins to taper.
E. Charge current tapers to l
OCT
. The current sense amplifier
output, in this case tied to the OC TERMINATE input,
goes high. The charger changes to the float state and
holds the battery voltage at V
F
.
F.
Here a load (>l
MAX
) begins to discharge the battery.
G. The load discharges the battery such that the battery
voltage falls below V
31
. The charger is now in state 1,
again.
UC2906
UC3906
OPERATION AND APPLICATION INFORMATION (continued)
Figure 2.
State Diagram and Design Equations for the Dual Level Float Charger
Figure 3.
Typical Charge Cycle: UC2906 Dual Level Float Charger
5
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