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| Fig.1 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831 |
The MCP73831 device is advanced linear charge management controllers for use in space-lim-ited, cost-sensitive applications.
Along with their small physical size, the low number of external components required make the MCP73831 ideally suited for por-table applications.
For applications charging from a USB port, the MCP73831 adhere to all the specifications governing the USB power bus.
The MCP73831 employ a constant-current and constant-voltage charge algorithm with selectable precondition-ing and charge termination.
The constant voltage regulation is fixed with four available options: 4.20V, 4.35V, 4.40V or 4.50V, to accommodate new, emerging battery charging requirements. The constant current value is set with one external resistor.
The MCP73831 device limit the charge current based on die temperature during high power or high ambient conditions.
This thermal regulation optimizes the charge cycle time while maintaining device reliability. Several options are available for the preconditioning threshold, preconditioning current value, charge termination value and automatic recharge threshold.
The preconditioning value and charge termination value are set as a ratio, or percentage, of the programmed constant current value.
The MCP73831 device is fully specified over the ambient temperature range of -40°C to +85°C.
The Circuit
The circuit is very simple and uses few external components which facilitates the assembly and reduces the assembly cost, the standard charging voltage regulation is normally set at 4.2V, but there are variations in the nomenclature of the last digit of the IC that differentiate them from the standard charging voltage such as:
- MCP73831-2 = 4.2V
- MCP73831-3 = 4.3V
- MCP73831-4 = 4.4V
- MCP73831-5 = 4.5V
The constant current charging value, is adjusted through resistor 2.2K ohms R3, which in our circuit is programmed for a ~450mA charge. Using a simple formula, we can vary this constant charging current:
Rc = charging resistor
CC = charging current in mA
Formula:
Cc = 1000/Rc
Being our 2.2K resistor, we have:
Cc = 1000/2.2
Cc = ~ 450mA
Remembering that the minimum charging current for this device is 15mA and the maximum current is 500mA.
Lithium Ion Batteries have become popular in large scale in portable electronic devices, due to them having higher energy density compared to other batteries on the market.
Benefits include thousands of recharges and none of the old, well-known "memory effect" problems we had in the first rechargeable NiCd battery cells.
However, lithium ion batteries must be charged following a carefully controlled constant current (CC) and constant voltage (CV) pattern that is unique to this type of cell.
Overloading and careless handling of a Li-Ion cell can cause permanent damage or instability and a potential danger of explosion.
In Figure 2 below, we have the 3.7V Li-Ion Battery Charger Circuit schematic diagram, with the MCP73831 IC and we can follow and analyze the entire circuit, which is a simple and easy-to-assemble circuit, with few external components.
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| Fig. 2 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831 |
Features
- Linear load management controller:
- Integrated pass-through transistor
- Integrated current direction
- Reverse Discharge Protection
- High precision preset voltage regulation: +0.75%
- Four voltage regulation options: 4.20V, 4.35V, 4.40V, 4.50V
- Programmable load current: 15 mA to 500 mA
- Selectable preconditioning: 10%, 20%, 40% or Disable
- Selectable end of charge control: 5%, 7.5%, 10% or 20%
- Three-state status output - MCP73831
- automatic shutdown
- Thermal regulation
- Temperature range: -40°C to +85°C
- Packaging: 5 derivations, SOT-23
- applications
- Lithium Ion / Lithium Polymer Battery Chargers
- Personal Data Assistants
- Mobile phones
- Digital cameras
- MP3 Players
- Bluetooth Headphones
- USB chargers
Components List
- U1 ...................... Integrated Circuit MCP73831
- LED1 ................. Light Emitting Diode - Red
- LED2 ................. Light Emitting Diode - Green
- R1, R2 ............... 240 Ohm Resistors
- R3 ...................... 2.2K Ohms Charging Program
- Others ................ Wires, connectors, PCI, tin etc.
We are offering the PCI - Printed Circuit Board, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home, or if you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.
Files to Download, Direct Link:
Click on the link beside: GERBER, PDF and PNG files
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