A5973AD
Up to 1.5 A step-down switching regulator for automotive
applications
Datasheet
-
production data
Applications
Dedicated to automotive applications
HSOP8 - exposed pad
Description
The A5973AD is a step-down monolithic power
switching regulator with a minimum switch current
limit of 1.8 A, so it is able to deliver up to 1.5 A DC
current to the load depending on the application
conditions. The output voltage can be set from
1.235 V to V
IN
. The high current level is also
achieved thanks to an HSOP8 package with an
exposed frame, that allows to reduce the R
th(JA)
down to approximately 40 °C/W. The device uses
an internal P-channel DMOS transistor (with
a typical R
DS(on)
of 250 m) as a switching
element to minimize the size of the external
components. An internal oscillator fixes the
switching frequency at 500 kHz. Having
a minimum input voltage of 4 V only it fits the
automotive applications requiring the device
operation even in cold crank conditions. A pulse-
by-pulse current limit with the internal frequency
modulation offers an effective constant current
short-circuit protection.
Features
Qualified following the AEC-Q100
requirements (see PPAP for more details)
1.5 A DC output current
Operating input voltage from 4 V to 36 V
3.3 V / (± 2%) reference voltage
Output voltage adjustable from 1.235 V to V
IN
Low dropout operation: 100% duty cycle
500 kHz internally fixed frequency
Voltage feed-forward
Zero load current operation
Internal current limiting
Inhibit for zero current consumption
Synchronization
Protection against feedback disconnection
Thermal shutdown
Figure 1. Application schematic
A5973AD
August 2014
This is information on a product in full production.
DocID13958 Rev 9
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Contents
A5973AD
Contents
1
Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1
1.2
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1
2.2
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3
4
5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Datasheet parameters over the temperature range . . . . . . . . . . . . . . . . 8
Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
Power supply and voltage reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Voltages monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Oscillator and synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Current protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Error amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
PWM comparator and power stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Inhibit function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6
Additional features and protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1
6.2
6.3
Feedback disconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Output overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Zero load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7
Closing the loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1
7.2
7.3
Error amplifier and compensation network . . . . . . . . . . . . . . . . . . . . . . . . 16
LC filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
PWM comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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A5973AD
Contents
8
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
8.10
Component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Positive buck-boost regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Negative buck-boost regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Synchronization example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Compensation network with MLCC at the output . . . . . . . . . . . . . . . . . . . 33
External SOFT_START network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9
10
11
12
Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
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Pin settings
A5973AD
1
1.1
Pin settings
Pin connection
Figure 2. Pin connection (top view)
1.2
Pin description
Table 1. Pin description
No.
1
2
3
4
5
6
7
8
Pin
OUT
SYNCH
INH
COMP
FB
VREF
GND
VCC
Regulator output.
Master/slave synchronization.
A logical signal (active high) disables the device. If INH not used the pin
must be grounded. When it is open an internal pull-up disables the
device.
E/A output for frequency compensation.
Feedback input. Connecting directly to this pin results in an output
voltage of 1.23 V. An external resistive divider is required for higher
output voltages.
3.3 V V
REF
. No cap is requested for stability.
Ground.
Unregulated DC input voltage.
Description
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DocID13958 Rev 9
A5973AD
Electrical data
2
2.1
Electrical data
Maximum ratings
Table 2. Absolute maximum ratings
Symbol
V
8
V
1
I
1
V
4
, V
5
V
3
V
2
P
TOT
T
J
T
STG
Input voltage
OUT pin DC voltage
OUT pin peak voltage at
t
= 0.1
s
Maximum output current
Analog pins
INH
SYNCH
Power dissipation at T
A
70 °C
Operating junction temperature range
Storage temperature range
Parameter
Value
40
-1 to 40
-5 to 40
Int. limit.
4
-0.3 to V
CC
-0.3 to 4
2
-40 to 150
-55 to 150
V
V
V
W
°C
°C
Unit
V
V
V
2.2
Thermal data
Table 3. Thermal data
Symbol
R
thJA
Parameter
Maximum thermal resistance junction ambient
Value
40
(1)
Unit
°C/W
1. Package mounted on the evaluation board.
DocID13958 Rev 9
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