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LM3647 Reference Design User’s Manual AN-1164
National Semiconductor
LM3647 Reference Design
Application Note 1164
March 2001
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
The LM3647 is a charge controller for Nickel-Cadmium
configurations. There are actually two different charge
(Ni-Cd), Nickel-Metal Hydride (Ni-MH) or Lithium-Ion (Li-Ion)
current regulation methods and these are referred to a
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The high speed PWM is filtered to a DC-level and fed into an operational amplifier that controls a power-NPN transistor. The LM3467 requires charge current feedback to control the charge current. 1.2 Modes of Operation 1.2.1 Charging Ni-Cd/Ni-MH Batteries AN101315-14 The charger detects that a battery is connected when the > CEL-pin 1.0V. The charger can also detect a battery that Charge Current has been deeply discharged and does not have any voltage The charge settings for LM3647 current contr
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AN-1164 and the charge process will restart. This occurs only with plyRejectionRatio), because they are both powered batteries that are already fully charged, and consequently directly from the unregulated DC-input. U1 must also should not be recharged. If the battery voltage has not have enough current drive to control the transistor Q3. U2 > reached the Li-Ion battery qualification voltage (CEL-pin should preferably have a low input offset, since this error 1.2V) within 1 minute of the Qualifi
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The actual timeouts (with RCIN @ 2.5 MHz) is: Phase Timeout Fast Charge ~ 330 Minutes Topping Charge ~ 80 Minutes EXAMPLE 2: AN101315-19 The actual timeouts (with RCIN @ 2.5 MHz) is: Phase Timeout Fast Charge Constant Current − 130 Minutes Topping Charge Constant Voltage − 190 Minutes 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 The resistor network (see the figure below) scales the resistor and the gain
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AN-1164 • For Li-Ion: Charge Phase: Duty Cycle: The voltage divider network for Li-Ion is very important. If the Soft Start 10% battery voltage is scaled too low, the battery will not attain its full capacity when charged, and if scaled too high, the Fast Charge 100% battery may become damaged. Never exceed the Topping Charge 10% recommended maximum voltage or current for a Li-Ion Maintenance Charge 5% battery! The dimensioning is done in the following manner. First calculate the maximum battery
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2.0 APPLICATION INFORMATION 2.1 Typical Example 2.1.1 Ni-Cd/Ni-MH AN101315-8 Set To: SEL1 SEL2 SEL3 V No Discharge before Charge Ni-MH Fast-PWM (LM3647 has current feedback) CC Hi-Z Discharge before Charge NA NA GND Maintenance Charge Only Ni-Cd Slow-PWM (external current control) www.national.com 6 AN-1164
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AN-1164 2.1.2 Li-Ion AN101315-9 Set To: SEL1 SEL2 SEL3 V After charging, maintenance charging until battery removal. NA 4.2V/Cell CC Hi-Z After charging, maintenance charging until battery removal. If battery Li-Ion NA voltage drops below a predefined value, the charger restarts the charge-process. GND After charging, no maintenance charging is applied. If battery voltage NA 4.1V/Cell drops below a predefined value, the charger restarts the charge-process. Note: When a three chemistry charger is
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3.0 LM3647 REFERENCE DESIGN DEMO-BOARD The demo-board provides a combined multi-chemistry The upper values correspond to a current sense resistor of solution with hardware for both external constant current 0.047Ω while the lower correspond to 0.100Ω (see previous source and LM3647 controlled charge current. Located near figure). 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 con
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LM3647 Reference Design User’s Manual AN-1164 AN101315-17 LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or 2. A critical component is any component of a life systems which, (a) are intended for surgical implant support device or system whose fai
