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- Voltage detector IC
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CN3781
4A, Standalone Li-ion Battery Charger IC
With Automatic Charge Current Adjustment
Product Profile
    Application Note
General Description
The CN3781 is a PWM switch-mode lithium ion battery charger controller for 1 cell li-ion battery in a small
package using few external components.
The CN3781 is specially designed for charging lithium ion batteries with constant current and constant
voltage mode. In constant voltage mode,the regulation voltage can be fixed at 4.2V with 1% accuracy,also
can be adjusted upward with an external resistor. The constant charge current is programmable with a single
current sense resistor.
An on-chip circuit block can automatically adjust charge current based on the output capability of input
supply, so CN3781 is ideally suited for the applications powered by the supply with limited output
capability, such as USB port, etc.
Deeply discharged batteries are automatically trickle charged at 17.5% of the full-scale current until the
cell voltage exceeds 66.5% of constant voltage. The charge cycle is terminated once the charge current
drops to 16% of full-scale current,and a new charge cycle automatically restarts if the battery voltage
falls below 95.5% of regulation voltage. CN3781 will automatically enter sleep mode when input voltage is
lower than battery voltage.
Other features include under voltage lockout,battery over voltage protection, status indication.
CN3781 is available in a space-saving 10-pin SSOP package.
Applications
Power Bank Portable Industrial and Medical Equipment
Hand-held Equipment Standalone Battery Chargers
Battery-Backup Systems
Features
On-chip circuit block can automatically adjust charge current based on the output capability of input
supply
Suited for the applications powered by the supply with limited output capability,such as USB port, etc.
Wide Input Voltage: 4.83V to 28V
Complete Charge Controller for single cell Lithium-ion Battery
Charge Current Up to 4A
High PWM Switching Frequency:300KHz
Regulation Voltage can be adjusted upward
Constant Voltage Accuracy: 1%
Charging Current is programmed with a current sense resistor
Automatic Conditioning of Deeply Discharged Batteries
Automatic Recharge
Charging Status Indication
Soft Start
Battery Overvoltage Protection
Operating Ambient Temperature 40 to 85
Available in 10 Pin SSOP Package
Pb-free, Rohs-Compliant, Halogen Free
Application Note
 Quick Start of CN376X Demo Board
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