A2550 Allegro MicroSystems, Inc., A2550 Datasheet - Page 11

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

A2550
Dropout Voltage
For operation with V
ing voltages, use the Pass Transistor On-Resistance R
to determine the maximum allowed regulator current,
I
V
Figure 3 shows the results of this condition combined with
the rated regulator current, in normal operation.
Note that, although the regulator is specified for normal
operation with V
in general thermal constraints will limit maximum opera-
tional V
Fault Logic
The A2550 offers several protection and fault detection
features. The operation of thermal shutdown, watchdog
monitoring of the microcontroller, and regulated voltage
undervoltage lockout are described in the Timing Diagrams
section. The fault logic is described in table 1.
REG5(max)
BB
and V
Table 1. Fault Logic
a
b
X indicates “don’t care,” Z indicates high impedence.
This entry is a logical OR of the EN and ENBAT pins.
BB
1
1
1
1
1
0
. This current is limited by the difference between
.
REG5
X
0
0
0
0
1
, according to the following equation:
BB
I
REG5
Inputs
well above normal automotive voltages,
BB
X
X
0
0
0
1
below the specified range of operat-
a
V
BB
R
X
X
X
0
0
1
REG5
V
REG5
X
X
X
X
0
1
1
1
1
1
1
0
Applications Information
Outputs
1
1
1
1
0
0
REG5
Pulse
Off
1
1
0
0
(1)
INx
Z
Z
Z
Z
Z
NPOR
The following faults generate a RESET state:
In addition, the following conditions cause a low NPOR
signal if the NPOR pin is pulled up by VREG5 (because
these conditions disable VREG5):
Figure 3. Current Capability of the 5 V Regulator (VREG5)
• watchdog alarm
• VREG5 falls below the UVLO level
• overtemperature (Thermal Shut Down)
• no ENABLE signal (EN = ENBAT = 0)
Relay Driver with 5 V Regulator
Normal Operation: OUTx active for INx active.
OCx disables OUTx only. OUTx latched OFF until INx
removed and reapplied.
NPOR periodically pulses to attempt RESET of
microcontroller.
NPOR remains active after UVLO recovers until POR
delay expires.
Sleep mode. NPOR = 0 when pulled up by VREG5
because VREG5 = 0.
70
60
50
40
30
20
10
0
0
for Automotive Applications
5
Mode of Operation
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
V
BB
10
(V)
15
20
11