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 (− DV)

·Maximum voltage

·Optional: Delta temperature/delta time (DT/Dt)

·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

National Semiconductor

Application Note 1164

March 2001

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

 

 

VCC

Ni-MH

GND

Ni-Cd

 

 

Hi-Z

Li-Ion

 

 

J2

Charge Mode

 

 

VCC

No discharge

GND

Maintenance charge only

 

 

Hi-Z

Discharge before charge

 

 

J2

Maintenance Mode

 

 

VCC

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

 

 

 

 

 

 

 

VCC

VCC

Fast

LM3647 controls charge current

 

GND

Slow

External (LM317) charge control

 

 

 

 

GND

VCC

Fast

LM3647 controls charge current

 

GND

Slow

External (LM317) charge control

 

 

 

 

Hi-Z

VCC

Fast

4.2V/Cell Li-Ion

 

GND

Fast

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 ²Ni 6-Cells² on J11 and J12:

LM3647 Reference Design User's Manual

AN-1164

© 2001 National Semiconductor Corporation

AN101315

www.national.com

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National Instruments LM3647 user manual General Description, KEY Features, Documentation Information, Jumper Settings

LM3647 specifications

The National Instruments LM3647 is a versatile and advanced power management integrated circuit designed specifically for applications in mobile and portable devices. This device provides an efficient power supply solution that caters to the demands of today's sophisticated electronics.

One of the main features of the LM3647 is its ability to deliver a highly accurate output voltage. With a low output voltage ripple, it ensures that sensitive components receive stable power, thereby enhancing the performance and reliability of the system. The device typically uses a constant on-time control scheme, which allows for rapid transient response and improves overall efficiency, especially during dynamic load changes common in portable devices.

The LM3647 offers an impressive input voltage range, typically from 2.5V to 5.5V, making it compatible with a wide range of power sources, including lithium-ion batteries and USB power. Additionally, the device is highly efficient, boasting peak efficiencies of over 95%. This efficiency translates to extended battery life, a crucial factor for portable electronics.

Another significant characteristic of the LM3647 is its integrated power path management capability. This feature allows it to intelligently manage power distribution between the battery and the load, ensuring seamless transitions between battery and wall power, and providing system protection from overloads and short circuits.

The LM3647 also supports a flexible output configuration, featuring multiple outputs that can be independently programmed. This flexibility is particularly beneficial in applications such as smartphones, tablets, and wearables that require multiple voltage rails for various components, including processors, displays, and sensors.

Moreover, the LM3647 incorporates advanced thermal management techniques. With a package designed to dissipate heat efficiently, it helps maintain operational stability and longevity of the device even under heavy load conditions.

In summary, the National Instruments LM3647 stands out as a high-performance power management IC leveraging cutting-edge technologies to provide efficient power solutions for mobile and portable devices. Its features, including high efficiency, accurate output voltage, integrated power path management, and flexible output configurations, combined with robust thermal characteristics, make it an excellent choice for designers aiming for optimal power management in their electronic devices.