Datasheet

Installation and Operation
© 2009 Microchip Technology Inc. DS51798A-page 13
2.3.1.5 MCP1631 PROGRAMMABLE CURRENT SOURCE AS BATTERY
CHARGER
The MCP1631HV Digitally Controlled Programmable Current Source Reference
Design reference board is provided with the LED driver firmware programmed into the
U2 microcontroller.
The reference board package also has compiled firmware
*.hex files included for
Li-Ion and NiMH/NiCd battery packs. There are two versions of charger firmware. One
is for Li-Ion cells (
00234R1-LiIon_Charger.hex) and the other is for NiCd/NIMH cells
(
00234R1-NiMH_NiCd_Charger.hex).
2.3.1.5.1 How to Connect and Charge a Battery with the MCP1631HV Digitally
Controlled Programmable Current Source Reference Design
To charge a battery pack with the MCP1631HV Digitally Controlled Programmable
Current Source Reference Design, the positive connector of the battery should be
connected to J2-1 (+). The negative terminal of the battery should be connected to
J2-5 (-).
A thermistor referenced to J2-5 (-) should be used for thermal shutdown if the battery
chemistry is NiMH/NiCd. To evaluate a NiMH/NiCd battery charger pack that does not
have an internal thermistor, it is recommended to attach an EPCOS Inc.
P/N: B57500M0103A005 thermistor onto one of the cells of the battery pack. This
thermistor should be connected to J2-4 (+) and J2-5 (-).
For evaluation, all charge parameters can be modified in source code. See the header
file
00234R1.h for the pre-processor definitions.
2.3.1.5.2 Charge Profiles
The pre-programmed parameters for the battery charge profiles are:
•Li-Ion
- Qualification: Precharge at 200 mA for V
CELL
< 3.0V
- Constant Current: 1A for 1 Cell, 0.5A for 2 Cells
- Constant Voltage: 4.20V (this value should be calibrated for better accuracy,
see Section 2.3.1.5.4 “Calibrating the Output Voltage for the Li-Ion
Chemistry Profile”)
- Charge Termination: 70 mA for 1 Cell and 2 Cells
- Overvoltage Detection: Once detected, attempts to restart the charge cycle 5
times. If overvoltage is still present, the charge cycle is aborted and the RED
LED is flashed.
• NiMH/NiCd
- Qualification: Precharge at 140 mA for V
CELL
< 0.9V
- Constant Current: 700 mA for 1 Cell to 4 Cell
- Terminate Fast Charge for -dV/dT or +dT/dt
- Top off Charge Current: 35 mA
Top off Charge Time: 1 hour
- Overvoltage Detection: Once detected, attempts to restart the charge cycle 5
times. If overvoltage is still present, the charge cycle is aborted and the RED
LED is flashed.
Note: The maximum charge current for the Li-Ion chemistry is programmed and
limited at 1A for a single cell (4.2V) or 500 mA for two cells in series
topology. The pre-programmed maximum charge current for NiMH/NiCd
chemistry is 700 mA.