A2550 Allegro MicroSystems, Inc., A2550 Datasheet - Page 14

• Manufacturer Part Number: A2550
• Description: Relay Driver With 5 V Regulator For Automotive Applications
• Manufacturer: Allegro MicroSystems, Inc.

A2550
A more rigorous derivation, including R
exponential current decay results in:
and
Energy loss in the driver is:
E
i
V
(
CL
t
)
V
R
DC
COIL
2
R
L
V
COIL
dc
t
COIL
R
L
COIL
COIL
1
R
V
COIL
Terminal List Table
CL
V
ln –
CL
No.
10
12
13
14
15
16
11
(
1
2
3
4
5
6
7
8
9
–
1
V
⎡
⎢
⎢
⎣
1
dc
V
dc
exp
1
V
VREG5
ENBAT
CL
ln
NPOR
CPOR
PGND
Name
LGND
OUT3
OUT2
OUT1
CWD
WDI
VBB
PAD
IN1
IN2
IN3
EN
)
1
COIL
t
1
R
L
.
V
COIL
COIL
dc
during the
V
VREG5
CL
NPOR
LGND
⎤
⎥
⎥
⎦
Activate driver 1
Activate driver 2
Activate driver 3
Logic ground; must be connected to PGND externally
Not Power-On Reset
WatchDog Input
Enable (low voltage)
5V regulator
Supply voltage
Enable (high voltage)
Capacitor terminal for Power-On Reset cycle time
Capacitor terminal for WatchDog timing
Power ground; must be connected to LGND externally
Low side driver 3
Low side driver 2
Low side driver 1
Exposed pad for enhanced thermal performance
WDI
IN1
IN2
IN3
EN
Pin-out Diagram
,
.
1
2
3
4
5
6
7
8
(17)
(18)
(19)
PAD
Capacitive Loads
When capacitive loads are applied to the outputs, the
constraint described below applies. Such is the case, for
example, when capacitors are attached to the outputs to
protect against ESD. Larger capacitors protect against larger
ESD voltages. However, the upper limit on capacitance is
determined by the blanking time. The latter allows for spuri-
ous current spikes and capacitor discharges to be completed
before the overcurrent detection circuit senses the output cur-
rent (see t
blanking time allows a 47 nF capacitor with 20% tolerance
and nominal 12 V automotive voltages.
Relay Driver with 5 V Regulator
16
15
14
13
12
10
11
9
Description
OUT1
OUT2
OUT3
PGND
CWD
CPOR
ENBAT
VBB
for Automotive Applications
BLANK
in the Electrical Characteristics table). The
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
14