Datasheet

124
8024A–AVR–04/08
ATmega8HVA/16HVA
23. Battery Protection
23.1 Features
• Short-circuit Protection
• Discharge Over-current Protection
• Charge Over-current Protection
• Discharge High-current Protection
• Charge High-current Protection
• Programmable and Lockable Detection Levels and Reaction Times
• Autonomous Operation Independent of CPU
23.2 Overview
The Current Battery Protection circuitry (CBP) monitors the charge and discharge current and
disables C-FET and D-FET if a Short-circuit, Over-current or High-current condition is detected.
There are five different programmable detection levels: Short-circuit Detection Level, Discharge
Over-current Detection Level, Charge Over-current Detection Level, Discharge High-current
Detection Level, Charge High-current Detection Level. There are three different programmable
delays for activating Current Battery Protection: Short-circuit Reaction Time, Over-current Reac-
tion Time and High-current Reaction Time. After Current Battery Protection has been activated,
the application software must re-enable the FETs. The Battery Protection hardware provides a
hold-off time of 1 second before software can re-enable the discharge FET. This provides safety
in case the application software should unintentionally re-enable the discharge FET too early.
The activation of a protection also issues an interrupt to the CPU. The battery protection inter-
rupts can be individually enabled and disabled by the CPU.
The effect of the various battery protection types is given in Table 23-1.
In order to reduce power consumption, Short-circuit, Discharge High-current and Discharge
Over-current Protection are automatically deactivated when the D-FET is disabled. The Charge
Over-current and Charge High-current Protection are disabled when the C-FET is disabled. Note
however that Charge Over-current Protection and Charge High-current Protection are never
automatically disabled when the chip is operated in DUVR mode.
Table 23-1. Effect of Battery Protection Types
Battery Protection Type Interrupt Requests C-FET D-FET MCU
Short-circuit Protection Entry Disabled Disabled Operational
Discharge Over-current
Protection
Entry Disabled Disabled Operational
Charge Over-current
Protection
Entry Disabled Disabled Operational
Discharge High-current
Protection
Entry Disabled Disabled Operational
Charge High-current
Protection
Entry Disabled Disabled Operational