Atmel AVR180, Примечание к применению

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AVR180
5
Power Consumption
The current consumption in normal operating mode (suffi-
ciently high V
CC
) is found by:
When reset switch or programmer force RESET to GND,
the current increases to:
When voltage drops to the level where the detector acti-
vates, transistor T1 closes, T2 opens and the current is:
As resistor R5 is usually chosen much smaller than the
other resistors R1-R4, the last two expressions both sim-
plify to:
I
V
CC
R1 R2
+
( )
R3 R4
+
( )
||
----------------------------------------------------------
 
 
V
CC
1
R1 R2 +
---------------------
1
R3 R4 +
--------------------- +
 
 
=
≈
I
V
CC
R1 R2
+
( )
R3 R4
+
( )
R5 R
RESET
|| || ||
-------------------------------------------------------------------------------------------------
≈
I
V
CC
R1 R2 +
( )
R5 R
RESET
|| ||
-----------------------------------------------------------------
≈
I
V
CC
R5 R
RESET
||
---------------------------------
≈
Table 1. Example Values
Component
Example Values
Recommended Tolerance 3.0V 4.5V
T1, T2 BC548 / BC848 / 2N3904 I
CE
≥
2.5 mA, V
CE
≥
8 V,
β
/h
FE
≥
100
T3 BC558 / BC858 / 2N3906 I
CE
≥
2.5 mA, V
CE
≥
8 V,
β
/h
FE
≥
100
R1 10 M
Ω ≤
1%
R2 1.54 M
Ω
976 k
Ω ≤
1%
R3 10 M
Ω ≤
20%
R4 3.3 M
Ω ≤
20%
R5 47 k
Ω ≤
20%
C1, C2, C3 100 nF
≤
20%, Z5U dielectric or better