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A2550 Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer A2550
Beschreibung Relay Driver
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 16 Seiten
A2550 Datasheet, Funktion
A2550
Relay Driver with 5 V Regulator
for Automotive Applications
Features and Benefits
Three independent low-side DMOS output drivers
Short-circuit protection of drivers
Eliminates need for flyback diodes on relays
Thermal shutdown
Separate precision 5 V regulator (2%)
Current clamp on 5 V regulator
16-pin TSSOP package with exposed thermal pad
Programmable reset (NPOR) delay time
Programmable watchdog
Automotive voltage and temperature ranges
Active clamps for automotive load dump specifications
Lead (Pb) free
Package: 16 pin TSSOP (suffix LP) with
exposed pad
Description
Large numbers of relay-based applications require the use of a
microprocessor which implements complex system control. In
these systems, there is the need for microprocessor logic supply
voltage, power-on reset circuitry, and watchdog capabilities.The
Allegro® A2550 combines the functions of voltage regulator,
watchdog, and reset, as well as three low-side DMOS relay
driver outputs. Primarily targeted at automotive applications,
this IC is designed to provide robust performance over extended
voltage and temperature ranges.
Three low-side DMOS drivers can drive inductive loads, such
as relay coils. Each driver integrates rugged voltage clamps
which survive automotive load dump pulses up to 48 V. The
40 V rating on VBB also ensures adequate survival in harsh
automotive environments.
A 5 V linear regulator provides 40 mA of output current, with
a tolerance of 2% over the operating temperature range. To
enhance the usefulness of the IC in automotive applications,
the 5 V regulator output, as well as the three low-side driver
outputs are protected against overcurrent conditions.
www.DataSheet4U.com
Approximate Scale
Continued on the next page…
Typical Application
System
Logic
1
IN1
OUT1 16
2
IN2
OUT2 15
3
IN3
A2550 OUT3 14
4
LGND
PGND 13
5
NPOR
CWD 12
6
WDI
CPOR 11
7
EN
ENBAT 10
8
VREG5
VBB 9
0.47 μF
X7R
Relays or other
inductive loads
2550-DS






A2550 Datasheet, Funktion
A2550
Relay Driver with 5 V Regulator
for Automotive Applications
Dynamic Thermal Impedance
Square Wave Power Pulse in a Single Output Stage
20
18
16
14
12
10
8
6
4
2
0
0.01
0.1
1 10 100
Time (ms)
Figure 1. Dynamic thermal impedance of an individual output stage during active clamp
of an inductive load
Nonrepetitive Output Active Clamp Power Dissipation
100
10 TJ = 25°C
TJ = 125°C
1
0.01
0.1
1
10 100
Time (ms)
Figure 2. Peak power dissipation curves for nonrepetitive clamped outputs. Output
voltage is clamped during turn-off of inductive loads while current decays.
Allegro MicroSystems, Inc.
6
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com

6 Page









A2550 pdf, datenblatt
A2550
Relay Driver with 5 V Regulator
for Automotive Applications
Applications Information
Dropout Voltage
For operation with VBB below the specified range of operat-
ing voltages, use the Pass Transistor On-Resistance RREG5
to determine the maximum allowed regulator current,
IREG5(max). This current is limited by the difference between
VBB and VREG5, according to the following equation:
I < V RVREG5
BB REG5
REG5
(1)
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 VBB well above normal automotive voltages,
in general thermal constraints will limit maximum opera-
tional VBB.
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.
Table 1. Fault Logica
Inputs
Outputs
NPOR
The following faults generate a RESET state:
• watchdog alarm
• VREG5 falls below the UVLO level
In addition, the following conditions cause a low NPOR
signal if the NPOR pin is pulled up by VREG5 (because
these conditions disable VREG5):
• overtemperature (Thermal Shut Down)
• no ENABLE signal (EN = ENBAT = 0)
70
60
50
40
30
20
10
0
0 5 10 15 20
VBB (V)
Figure 3. Current Capability of the 5 V Regulator (VREG5)
Mode of Operation
1 0 0 0 0 1 1 1 INx Normal Operation: OUTx active for INx active.
1
0
0
0
1
1
1
1
Z
OCx disables OUTx only. OUTx latched OFF until INx
removed and reapplied.
1
0
0
1
X
1
1
Pulse
Z
NPOR periodically pulses to attempt RESET of
microcontroller.
1
0
1
X
X
1
1
0
Z
NPOR remains active after UVLO recovers until POR
delay expires.
1 1XXX1 0 0Z
0 X X X X 0 0 Off
aX indicates “don’t care,” Z indicates high impedence.
bThis entry is a logical OR of the EN and ENBAT pins.
Z
Sleep mode. NPOR = 0 when pulled up by VREG5
because VREG5 = 0.
Allegro MicroSystems, Inc.
12
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com

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