AS1720
Datasheet - Application Information
9 Application Information
In order to drive relays, which need more than 100mA current, an external circuitry (see Figure 11) can be used. This application shows how to
drive 5W @12V relays.
This circuit is only applicable for AS1720A.
For this example with R1 = 100Ω and RS = 2.5Ω the current Is is calculated as follows:
IS
=
I1
×
R----1- =
RS
0, 01A × 12---,-0---50-=
400mA
(EQ 3)
Figure 11. AS1720A - Typical Application
Vsupply: +12V
VDDHV
100nF
VDDA
DUTY
AS1720A
10mA
IS
R1
100Ω 1V
RS
I1
OUT
-
+
LM741
BC161
VSS
Relay
Free-
Wheeling
Diode
ENN
IE
RIE
120kΩ
Energising Current adjust
IH
RIH
240kΩ
Hold Current adjust
www.austriamicrosystems.com/Solenoid-Relay-Driver/AS1720 Revision 1.04
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