National Instruments Network Card LM3647 User Manual

National Semiconductor  
Application Note 1164  
March 2001  
LM3647 Reference Design  
User’s Manual  
GENERAL DESCRIPTION  
application. The demo-board has extra components to  
make it simple for the user to try out different batteries and  
configurations. There are actually two different charge  
current regulation methods and these are referred to as fast  
and slow (LM317).  
The LM3647 is a charge controller for Nickel-Cadmium  
(Ni-Cd), Nickel-Metal Hydride (Ni-MH) or Lithium-Ion (Li-Ion)  
batteries. The device uses a pulsed-current charging or a  
constant-current charging technique. The device can also be  
configured to discharge before charging. Throughout the  
charging sequence the LM3647 monitors voltage and/or  
temperature and time in order to terminate charging.  
JUMPER SETTINGS  
J5  
VCC  
Type Select  
Negative delta voltage (−V)  
Maximum voltage  
Ni-MH  
Ni-Cd  
Li-Ion  
GND  
Hi-Z  
Optional: Delta temperature/delta time (T/t)  
Optional: Maximum temperature  
Backup: Maximum time  
J2  
VCC  
GND  
Hi-Z  
Charge Mode  
No discharge  
The LM3647 is user configurable for three battery  
chemistries: Ni-Cd, Ni-MH or Li-Ion.  
Maintenance charge only  
Discharge before charge  
In Ni-Cd/Ni-MH mode, four different charging phases are  
used:  
J2  
VCC  
GND  
Maintenance Mode  
Softstart charge  
Fast charge  
Charge indefinitely  
No charge and restart fast-charge if battery  
becomes discharged  
Topping charge  
Maintenance charge  
Hi-Z  
Charge indifinitely and restart fast-charge if  
battery becomes discharged  
In Li-Ion mode, four different charging stages are used:  
Qualification  
Fast Charge Phase 1, Constant Current  
Fast Charge phase 2, Constant Voltage  
Maintenance charge  
Regulation Method / Cell  
J5  
J6  
J7  
Voltage  
VCC  
VCC Fast LM3647 controls charge current  
GND Slow External (LM317) charge control  
KEY FEATURES  
GND VCC Fast LM3647 controls charge current  
GND Slow External (LM317) charge control  
Auto-adaptive fast charge  
High-resolution, accurate voltage monitoring prevents  
Li-Ion under-charge or overcharge  
Hi-Z VCC Fast 4.2V/Cell Li-Ion  
GND Fast 4.1V/Cell Li-Ion  
Fast charge, pre-charge and maintenance currents are  
provided. Different currents are selectable via external  
resistors  
Timeout  
Timeout settings J18 (set according to charge-rate C), See  
Section 3.0 for more information.  
Fast-charge termination by temperature/time, maximum  
voltage, maximum temperature and maximum time  
Temperature Input  
Dynamically detects battery insertion, removal, short  
circuit and bad battery without additional hardware  
The optional Temperature input is connected to J3 and if not  
used Short J8.  
Supports charging of battery packs with 2-8 cells of  
Ni-Cd, Ni-MH or 1-4 cells of Li-Ion  
Voltage Regulation Range  
Three LED indicators and one Buzzer output indicate  
operational modes  
Voltage regulation loop setting J14 (not used with external  
LM317 regulation I.e. J7 = slow), defines maximum voltage  
output. See also Section 3.0 LM3647 REFERENCE  
DESIGN DEMO-BOARD.  
Ni-MH/Ni-Cd charge mode, Li-Ion charge mode or  
discharge mode can be selected manually  
PWM switching controller  
Voltage Measurement  
DOCUMENTATION INFORMATION  
The battery voltage is selected with the Voltage jumpers J11  
& J12 depending on number of cells/chemistry. For instance,  
a 9V Ni-Cd block battery has 6 cells in it and therefore needs  
the jumper at Ni 6-Cellson J11 and J12:  
The following documentation describes how to use the  
LM3647 demo-board and also gives a few tips on design  
calculations. Please note that not all components on the  
demo-board are used when designing  
a
charger  
© 2001 National Semiconductor Corporation  
AN101315  
 
and the charge process will restart. This occurs only with  
batteries that are already fully charged, and consequently  
should not be recharged. If the battery voltage has not  
plyRejectionRatio), because they are both powered  
directly from the unregulated DC-input. U1 must also  
have enough current drive to control the transistor Q3. U2  
should preferably have a low input offset, since this error  
will be amplified.  
>
reached the Li-Ion battery qualification voltage (CEL-pin  
1.2V) within 1 minute of the Qualification Phase, the battery  
is considered to be defective, and the charger goes into error  
The regulator IC2 criteria is that it has to be able to  
handle the input DC-voltage, and deliver enough current  
to drive the circuitry (all LED’s, buzzer, LM3647).  
<
mode. It stays there until the battery is removed (CEL-pin  
1.0V).  
The next phase is Fast Charge Constant Current. During this  
phase the current is constant, and the battery voltage will  
slowly rise (due to the charging). When the battery has  
reached its maximum battery voltage (CEL at 2.675V or  
2.74V, depending on SEL3, it will go to the next phase which  
is Fast Charge Constant Voltage.  
The transistor Q3 must be able to handle the charge  
current and (depending on charge current) must be  
provided with an adequate heatsink.  
The transistor Q2 must be able to handle the maximum  
discharge current.  
The Diode D1 must be able to handle the maximum  
charge current.  
During this phase, the charger will keep the voltage constant  
and stay in this phase until the current has decreased to a  
threshold value (CS at 2.3V).  
1.2.2.2 Clarifications Regarding Circuit Schematics  
The battery is now fully charged, and the charger can  
behave in different modes, depending on SEL1. It can either  
maintenance charge the battery and restart the charge  
process if the battery voltage drops below the maintenance  
The circuitry with Q4, R26 and R27 (see section below) is  
used to protect the battery from excessive charge current.  
When the current flows through the current sense resistor  
R9, and is amplified by U2, the voltage at U2’s output drops  
from 2.5V until Q4 starts conducting. It discharges the  
RC-network that generates the DC-voltage from the  
PWM-output of the LM3647.  
<
restart threshold value (CEL 2.153V), or just maintenance  
charge the battery and don’t restart the charge process if the  
battery becomes discharged. The last mode is no  
maintenance charge, and restarts the charge process if the  
battery voltage drops below the maintenance restart  
1.2.2.3 Setting The Charge Timeout  
<
threshold value (CEL 2.153V).  
The LM3647 uses the charge timeout value as a backup  
termination method if the normal termination methods fail.  
The charge timeout also controls the length of some of the  
phases like the Topping Charge phase (Ni-Cd/Ni-MH). The  
timeout is selectable from a charge rate of 3.2C to 0.4C. The  
table below shows which values will result in a certain  
timeout.  
1.2.2.1 Components Critical to Total Charger  
Performance  
The capacitance C2 connected to CEXT must be of a  
type that has low internal resistance, low loss, high  
stability and low dielectric absorption. The capacitance  
mounted on the Demo Board is a metallized polyester  
type from WIMA, 2220 series.  
The operational amplifiers U1 and U2 must be capable of  
rail-to-rail output, and have a high PSRR (PowerSup-  
TABLE 1. Charge Timeouts  
Ni-Cd/Ni-MH  
Ni-Cd/Ni-MH  
Li-lon CC  
(minutes)  
Li-lon CV  
(minutes)  
Appropriate  
R Value  
C Value  
Fast Charge  
(minutes)  
75  
Topping (minutes)  
Charge Rates  
100 kΩ  
100 kΩ  
100 kΩ  
100 kΩ  
100 kΩ  
100 kΩ  
100 kΩ  
100 kΩ  
0 nF  
10 nF  
15 nF  
22 nF  
33 nF  
47 nF  
68 nF  
100 nF  
20  
25  
50  
75  
3.2C  
2.4C  
1.4C  
1.2C  
0.9C  
0.7C  
0.5C  
0.4C  
100  
70  
100  
160  
190  
260  
330  
450  
540  
160  
40  
110  
130  
170  
220  
300  
360  
190  
50  
260  
65  
330  
80  
450  
115  
135  
540  
EXAMPLE 1:  
AN101315-18  
3
 
@
The actual timeouts (with RCIN 2.5 MHz) is:  
Phase  
Timeout  
330 Minutes  
80 Minutes  
Fast Charge  
Topping Charge  
EXAMPLE 2:  
AN101315-19  
@
The actual timeouts (with RCIN 2.5 MHz) is:  
Phase  
Timeout  
Fast Charge Constant Current  
− 130 Minutes  
− 190 Minutes  
Topping Charge Constant Voltage  
1.2.2.4 Setting The Charge Current  
1.2.2.5 Setting Maximum Battery Voltage  
The charge-current is selected by setting the current sensing  
resistor and the gain of the differential amplification stage.  
The current sensing resistor (R5) should be dimensioned  
such that the voltage drop over it is not too small, since the  
signal will be more susceptible to noise and offsets in the  
amplification-stage. The resistance should not be too large  
either (especially in high-current applications), because this  
will only generate more heat from the component. A suitable  
value is one where 50 mV dropped across the resistor when  
maximum current flows through it. The differential signal is  
then amplified, inverted and centered around the 2.5V  
reference by the operational amplifier and fed to the CS pin  
on the LM3647. The gain must be dimensioned by setting  
the appropriate ratio between R1 (R2) and R3 (R4). The  
figure below is dimensioned for a maximum current of about  
1.1A. This was dimensioned using the following formula:  
The resistor network (see the figure below) scales the  
battery voltage to a suitable level for the LM3647. For  
Ni-Cd/Ni-MH batteries the network is less critical, but limits  
the maximum battery voltage, it is only used as a backup  
termination method. For Li-Ion batteries the network must be  
more accurate, requiring precision resistors with low  
tolerances.  
For Ni-Cd/Ni-MH:  
The dimensioning is accomplished in the following manner:  
First calculate the maximum battery voltage for the specific  
battery pack. See example below.  
BatteryVoltage/Cell = 1.2V NumberOfCells = 5  
PackVoltage = 1.2x5 = 6V  
Battery-  
MaximumBatteryVoltage/Cell = 1.85V  
MaximumBattery-  
Voltage = 1.85x5 = 9.25V  
When the Maximum Battery Voltage has been determined,  
the voltage divider network has to be dimensioned using the  
following formula:  
AN101315-3  
AN101315-2  
AN101315-4  
4
 
For Li-Ion:  
Charge Phase:  
Soft Start  
Duty Cycle:  
10%  
The voltage divider network for Li-Ion is very important. If the  
battery voltage is scaled too low, the battery will not attain its  
full capacity when charged, and if scaled too high, the  
battery may become damaged. Never exceed the  
recommended maximum voltage or current for a Li-Ion  
battery!  
Fast Charge  
100%  
10%  
Topping Charge  
Maintenance Charge  
5%  
The dimensioning is done in the following manner.  
First calculate the maximum battery voltage for the specific  
battery pack. See example below.  
BatteryVoltage/Cell = 3.6V NumberOfCells = 2  
PackVoltage = 3.6x2 = 7.2V  
Battery-  
MaximumBatteryVoltage/Cell = 4.1V  
MaximumBattery-  
Voltage = 4.1x2 = 8.2V  
When the maximum battery voltage has been determined,  
the voltage divider network has to be dimensioned using the  
following formula:  
The LM3647 has two different regulation voltages, which the  
user can select. These are 2.675V (SEL3 tied to GND) and  
2.740V (SEL3 tied to VCC). This selection pin can be used to  
configure the charger to regulate for different input voltages  
so that the charger can handle both 3.6V- and 3.7V-cells,  
without changing the resistor values in the divider network.  
SEL3 can also be used if there is problem in finding the right  
values in the resistor network. The recommended tolerance  
of the resistors are 0.1%, but 1% may be used with a  
marginal loss of battery capacity by subtracting the tolerance  
of the divider network from the maximum battery voltage.  
Using the LM3647 without current feedback, for  
Ni-Cd/Ni-MH only (slow PWM mode):  
This mode uses an external constant-current power-source,  
which is switched on and off according to the charge-phase  
of the LM3647. The frequency is approximately 0.1 Hz. The  
advantage of this charge method is that operational  
amplifiers and the current feedback circuitry are not needed,  
which provides a low-cost solution. The dimensioning of the  
voltage divider network is performed the same way. The  
constant current source is dimensioned in the following  
manner:  
AN101315-7  
The LM3647 regulates the constant current source by  
turning the transistor Q1 on and off.  
When the transistor is off, the LM317T regulator feeds a  
constant current to the battery (at V_OUT).  
When the transistor is on, the output from the LM317 is  
limited to 1.25V (which should be greater than the battery  
voltage).  
5
 
2.0 APPLICATION INFORMATION  
2.1 Typical Example  
2.1.1 Ni-Cd/Ni-MH  
AN101315-8  
Set To:  
VCC  
SEL1  
SEL2  
Ni-MH  
SEL3  
No Discharge before Charge  
Discharge before Charge  
Maintenance Charge Only  
Fast-PWM (LM3647 has current feedback)  
NA  
Hi-Z  
NA  
GND  
Ni-Cd  
Slow-PWM (external current control)  
6
 
2.1.2 Li-Ion  
AN101315-9  
Set To:  
VCC  
SEL1  
SEL2  
SEL3  
After charging, maintenance charging until battery removal.  
NA  
4.2V/Cell  
Hi-Z  
After charging, maintenance charging until battery removal. If battery  
voltage drops below a predefined value, the charger restarts the  
charge-process.  
Li-Ion  
NA  
GND  
After charging, no maintenance charging is applied. If battery voltage  
drops below a predefined value, the charger restarts the charge-process.  
NA  
4.1V/Cell  
Note: When a three chemistry charger is designed, special considerations must be taken into account regarding configuration pin SEL3. this pin has differnet  
meanings when switching between Ni-Cd/Ni-MH and Li-Ion. To ensure correct operation, the SEL3-pin MUST be tied to VCC. If Li-Ion cells of 4.1V/Cells is  
used, then minor adjustments have to be done to the voltage measurement resistor divider.  
7
 
3.0 LM3647 REFERENCE DESIGN DEMO-BOARD  
The demo-board provides combined multi-chemistry  
a
The upper values correspond to a current sense resistor of  
0.047while the lower correspond to 0.100(see previous  
figure).  
solution with hardware for both external constant current  
source and LM3647 controlled charge current. Located near  
the top-left corner of the board is the power supply connector  
(next to the heatsink). When using the external constant  
current source, a power resistor needs to be connected at  
the connector marked 317-resistor. The values of the resistor  
can be calculated using the equation 4 mentioned earlier.  
At the bottom-right corner of the board are two connectors  
that lead to the battery and discharge resistor. The value of  
the discharge resistor depends on the battery pack voltage  
and the maximum discharge rate. The demo-board has  
different jumpers that are assigned to different setups. Some  
of the components are not populated, providing support for  
user-specific values.  
AN101315-13  
The battery voltage is selected with the Voltage jumpers J11  
and J12 (see below for settings).  
The timeout jumper J18 is used to select different timeouts  
from 2.4C to 0.4C. The values mounted on the demo-board  
result in timeouts corresponding to the charge-rates shown  
below:  
AN101315-14  
The jumper J3 is used to connect to an optional  
NTC-resistor. If no temperature sensor is used, the jumper  
J8 must be shorted. The Demo-board was designed for an  
NTC thermistor from Siemens (B57861S302F40) with the  
AN101315-10  
The PWM jumper J7 is used to connect the PWM-signal to  
either the external constant current source (marked slow) or  
the RC-filter that is connected to the operational amplifier  
(marked fast).  
@
following specifications: 3kΩ  
25˚C, β = 3988. If an NTC  
with different characteristics is used, then the resistor R28  
may need to be changed. The charger uses voltage levels to  
trigger under/over temperature conditions. The voltage at the  
temperature-input must be between 2.2V or 0.5V for the  
charger to start. During charging the voltage must stay  
between 3.0V for Li-Ion, or 3.15V for Ni-Cd/Ni-MH, and 0.5V  
or the charger will register a temperature fault and abort the  
charge.  
The PWM-FB jumper J14 is used to select different  
amplification levels of the PWM signal. The jumper with the  
battery voltage ranges are shown below:  
AN101315-11  
AN101315-15  
The I jumper J10 is used to select between different current  
sense resistors. The values mounted are 0.047and  
0.100.  
AN101315-12  
The different current sense voltage amplification level is  
selected via CURRENT jumpers J9 and J13 (both jumpers  
must be changed in pairs, see figure below).  
AN101315-16  
The three jumpers J2, J5 and J6 are connected to the three  
selection-pins SEL1, SEL2 and SEL3. These jumpers are  
used to select how the charger should behave (see Charger  
Modes table).  
8
 
AN101315-17  
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