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LM3647 Reference Design
User’s Manual

GENERAL DESCRIPTION

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.

Negative delta voltage (−

V)

Maximum voltage

Optional: Delta temperature/delta time (

T/

t)

Optional: Maximum temperature

Backup: Maximum time

The

LM3647

is

user

configurable

for

three

battery

chemistries: Ni-Cd, Ni-MH or Li-Ion.

In Ni-Cd/Ni-MH mode, four different charging phases are
used:

Softstart charge

Fast charge

Topping charge

Maintenance charge

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

KEY FEATURES

Auto-adaptive fast charge

High-resolution, accurate voltage monitoring prevents
Li-Ion under-charge or overcharge

Fast charge, pre-charge and maintenance currents are
provided. Different currents are selectable via external
resistors

Fast-charge termination by temperature/time, maximum
voltage, maximum temperature and maximum time

Dynamically detects battery insertion, removal, short
circuit and bad battery without additional hardware

Supports charging of battery packs with 2-8 cells of
Ni-Cd, Ni-MH or 1-4 cells of Li-Ion

Three LED indicators and one Buzzer output indicate
operational modes

Ni-MH/Ni-Cd charge mode, Li-Ion charge mode or
discharge mode can be selected manually

PWM switching controller

DOCUMENTATION INFORMATION

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

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).

JUMPER SETTINGS

J5

Type Select

V

CC

Ni-MH

GND

Ni-Cd

Hi-Z

Li-Ion

J2

Charge Mode

V

CC

No discharge

GND

Maintenance charge only

Hi-Z

Discharge before charge

J2

Maintenance Mode

V

CC

Charge indefinitely

GND

No charge and restart fast-charge if battery
becomes discharged

Hi-Z

Charge indifinitely and restart fast-charge if
battery becomes discharged

J5

J6

J7

Regulation Method / Cell

Voltage

V

CC

V

CC

GND

Fast

Slow

LM3647 controls charge current
External (LM317) charge control

GND

V

CC

GND

Fast

Slow

LM3647 controls charge current
External (LM317) charge control

Hi-Z

V

CC

GND

Fast
Fast

4.2V/Cell Li-Ion
4.1V/Cell Li-Ion

Timeout

Timeout settings J18 (set according to charge-rate C), See
Section 3.0 for more information.

Temperature Input

The optional Temperature input is connected to J3 and if not
used Short J8.

Voltage Regulation Range

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.

Voltage Measurement

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-Cells

on J11 and J12:

National Semiconductor
Application Note 1164
March 2001

LM3647

Reference

Design

User’s

Manual

AN-1

164

© 2001 National Semiconductor Corporation

AN101315

www.national.com

Содержание LM3647

Страница 1: ...N INFORMATION 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 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 r...

Страница 2: ...in range to start charging If it is then it applies a small current of 0 2C for approximately 5 minutes If the battery voltage exceeds the maximum battery voltage CEL pin 3 017V the LM3647 stops charging and stays in error mode until the battery is removed If the battery voltage has not risen above the bad battery threshold CEL pin 1 2V then the battery is considered to be defective and the charge...

Страница 3: ...output and have a high PSRR PowerSup 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 The regulator IC2 criteria is that it has to be able to handle the input DC voltage and deliver enough current to drive the circ...

Страница 4: ...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 1 2 2 5 Setting Maximum Battery Voltage The resistor network see the figure below scales the battery voltage to a suitable level for the LM...

Страница 5: ...EL3 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...

Страница 6: ...1 1 Ni Cd Ni MH Set To SEL1 SEL2 SEL3 VCC No Discharge before Charge Ni MH Fast PWM LM3647 has current feedback Hi Z Discharge before Charge NA NA GND Maintenance Charge Only Ni Cd Slow PWM external current control AN101315 8 AN 1164 www national com 6 ...

Страница 7: ...f 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 Cell...

Страница 8: ...gnal The jumper with the battery voltage ranges are shown below The I jumper J10 is used to select between different current sense resistors The values mounted are 0 047Ω and 0 100Ω 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 The upper values correspond to a current sense resistor of 0 047...

Страница 9: ...n be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness National Semiconductor Corporation Americas Tel 1 800 272 9959 Fax 1 800 737 7018 Email support nsc com National Semiconductor Europe Fax 49 0 180 530 85 86 Email europe support nsc com Deutsch Tel 49 0 69 9508 6208 English Tel 44 0 870 24 0 2171 Français Tel 33 0 1 41 91 879...

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