General Description

LM3647 Reference Design User's Manual

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
J5	J6	J7	Voltage
			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

AN101315