Rainbow Electronics ATmega8HVD - Manual (Page 4)

4
8052B–AVR–09/08
ATmega4HVD/8HVD
2. Overview
The ATmega4HVD/8HVD is a monitoring and protection circuit for 1-cell Li-ion applications
with focus on high security/authentication, low cost and high utilization of the cell energy. The
device contains secure authentication features as well as autonomous battery protection dur-
ing charging and discharging. The External Protection Input can be used to implement other
battery protection mechanisms using external components, e.g. protection against chargers
with too high charge voltage can be easily implemented with a few low cost passive compo-
nents. The feature set makes the ATmega4HVD/8HVD a key component in any system
focusing on high security, battery protection, high system utilization and low cost.
Figure 2-1. Block Diagram
An integrated, low-dropout linear regulator that can handle input voltages as low as 2.1V,
ensures that the stored energy can be fully exploited. The regulator capabilities, combined
with a extremely low power consumption in the power saving modes, greatly enhances the cell
energy utilization compared to existing solutions.
The chip utilizes Atmel's Deep Under-voltage Recovery (DUVR) mode that supports pre-
charging of deeply discharged battery cells without using a separate Pre-charge FET. An
enhanced start-up scheme allows the chip to operate correctly even with only Discharge FET
connected. This makes it possible to further reduce system cost for applications that do not
require Charge Over-current protection.
The ATmega4HVD/8HVD contains a 10-bit ADC for cell voltage measurements. The ADC is
also used to monitor the on-chip temperature. Temperature is measured by the integrated
Voltage Reference, which contains a built-in temperature sensor. ATmega4HVD/8HVD con-
PORTC (2)
SRAM Flash
CPU
EEPROM GND
OC
OD FET
Control
Voltage
ADC
Voltage
Reference
GND
VCC
RESET/dW
Power
Supervision
POR &
RESET
Watchdog
Oscillator
Watchdog
Timer
Oscillator
Circuits /
Clock
Generation
PC1:0
8/16-bit T/C1
8/16-bit T/C0
PORTB (3)
PB2:0
SPI
Voltage
Regulator
Charger
Detect
VFET
VREG
BATT
PV1
DATA BUS
Battery
Protection
Security
Module
Voltage Regulator
Monitor Interface
PB2 (CKOUT)
Oscillator
Sampling
Interface
Program
Logic
debugWIRE
NI
PC1 (External Protection Input)
PB0 (ADC0)