Datasheet

CTI – SOFTWARE DEVELOPMENT GROUP
© 2008 Electrolux Major Appliances Europe, All rights reserved
34
File: AMI technical Guide v1.pdf - Date: 04/02/2008
The maximum power dissipation for this component can be therefore calculated under the
above mentioned conditions that is P
DMAX
=0.574W. Then maximum output current for different
values of VIN can be listed, considering a gain factor g=0.8:
V
IN
ΔV to 5V
OUT_MAX
I
D
MAX
P
gV
=
⋅Δ
7.5V 2.5V 287mA
9V 4V 179mA
12V 7V 102mA
Table 6.1
MAX253CSA+ (Maxim) power-driver designed to provide isolated power to the circuit.
Datasheet parameters:
• T
J
max : 150 °C
• T
A
range : 0 ÷70 °C
• The maximum allowable power dissipation is 1W
6.2.2. AMI Power out:
LE50ABZ (STM) fixed positive voltage regulator. Datasheet parameters:
• Output current limit : 150mA min
• T
J
range : -40 ÷125 °C
• T
A
range : -40 ÷125 °C
• Dropout voltage (@I
O
= 100 mA): typ. 0.2V
Summarizing, output current limit is fixed to 150mA given by LE50ABZ. Above this value,
and particularly for external +12V supply, power consumption of LM340MP-5 rises over
PDMAX with a consequent increase of junction temperature even up to TJMAX causing
component thermal shutdown; for example if Iout=200mA and Vin=12V, PD=1.12W, 546mW
above calculated limit.
 PC laptop supplied by battery (+5V [V
CC
] tolerance is ±5%) like worst case for USB
AMI feeding.
Like in the situation explained previously LE50ABZ limits output current value to 150mA.
Above this value output voltage falls down drastically like displayed in
Table 6.2 and chart in
Fig. 32 due to “not stabilized” +5V voltage supplied by laptop battery.