ATMEGA8HVD-4MX Atmel, ATMEGA8HVD-4MX Datasheet - Page 101

• Manufacturer Part Number: ATMEGA8HVD-4MX
• Description: MCU AVR 8K FLASH 2.1-8V 4MHZ QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8HVD-4MX

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 4MHz
• Peripherals: POR, WDT
• Number Of I /o: 5
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 2.4 V
• Data Converters: A/D 1x10b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 18-MLF® Exposed Pad (Staggered Leads), DFN
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Connectivity: -

19.3
19.4
8052B–AVR–09/08
Battery Pack Short mode
Regulator Force mode
The Voltage Regulator has a separate Short-Circuit Detection mode (RSCD) that can be
enabled or disabled by SW. This mode should always be enabled except when operating at
VFET voltages below V
operation during short spikes on VFET that can occur for instance during a battery pack inser-
tion. The mode is entered when VFET drops below V
Detection is enabled. In the Battery Pack Short mode, VFET is temporarily disconnected from
VREG to avoid a quick drop in the voltage regulator output. The chip will be completely pow-
ered by the external reservoir capacitor (CREG). This allows the chip to operate a certain time
before entering BLOD reset (power-off) even if the VFET voltage is too low for the voltage reg-
ulator to operate.
The maximum time that the chip can operate in the Battery Pack Short mode is given by the
size of the external reservoir capacitor and the actual power drawn from VREG. The VREG
voltage must stay above V
short occurs when VREG = 2.2V and V
by:
where I
I
Regulator Short-circuit Detection.
The regulator Force mode is designed to be able to operate the chip even at very low cell volt-
ages. This mode is automatically entered when the VFET voltage drops below V
provided that the Regulator Short-circuit Detection is disabled. To ensure operation down to
minimum VFET level, Regulator Short-circuit Detection should always be disabled before
VFET reaches V
An example of VREG voltage as function of VFET when using the voltage regulator as
intended, is shown in figure 66. When VFET > V
value). When VFET approaches V
when VFET passes V
nuity in VREG can be observed. This is caused by the fact that VREG is no longer regulated
and is forced as close to VFET as possible. A small difference V
VREG can be observed. This voltage drop depends on the load current. Typical vales can be
found in TBD-El.Chara. The chip will continue operation in FORCE mode until VREG reaches
the BLOD level and the chip enters power-off.
When using VREG as reference for external measurements, for instance as reference for an
external thermistor as shown in TBD-operating circuit, it may be required to know the accurate
value of VREG. In FORCE mode, VREG will range from V
normal regulation where VREG has a constant value. Since ATmega4/8HVD has no method
of measuring VREG directly, it is recommended to measure the cell voltage and estimate
VREG based on loss through Charge FET (if applied) and voltage drop from VFET to VREG
according to the following formula:
AVG
= 100 µA, this time equals 4.4 ms. Refer to
AVG
represents the average current drawn from CREG. For CREG = 2.2 µF and
FORCE-
FORCE-
during discharge.
FORCE
BLOT,normal
, the regulator enters FORCE mode. When this occurs, a disconti-
VREG
(see TBD-electrical chara). The mode is intended for sustaining
FORCE
T
FORCE
=
to avoid that the chip enters power-off. If a battery pack
c Δ(v)
----------------- -
BLOT, normal
I
⋅
=
AVG
, Regulator Short-circuit Detection is disabled, and
V
Cell
=
–
CREG 0.2V
---------------------------------
V
is 2.0V the chip can operate for a time given
Table 19-2 on page 102
FORCE
DS CFET
I
AVG
–
⋅
ATmega4HVD/8HVD
, VREG is regulated to 2.2V (nominal
FORCE
–
V
FORCE
DROP
and Regulator Short-circuit
to VFET
DROP
between VFET and
min
for an example of
, as opposed to
FORCE-
101