AS8401
Multipurpose control ASIC
for OMNIFET
Data Sheet
Austria Mikro Systeme International AG
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 2 of 11
Austria Mikro Systeme International AG
K e y F e a t u r e s
Multipurpose control ASIC for OMNIFET (SGS Thompson intelligent power FET family)
Contains one channel on-chip
Applicable in low or high side switch circuits
Supply voltage range 10V 60V
Up to +/- 3V potential difference between system's digital ground and power ground possi-
ble.
Current controlled interface
Provides load circuit surveillance and fault back signal
Typical rise time shorter then 2.4us
Typical fall time shorter then 3.8us
8 pin SOIC Package
G e n e r a l D e s c r i p t i o n
The ASIC's purpose is to drive one OMNIFET n-channel power FET device. (OMNIFET is a
trademark of SGS-THOMSON). The OMNIFET's integrated protection circuits (current limita-
tion, over temperature protection, ...) are supplied via the OMNIFET's gate input. Thus in the
OMNIFET's on-state, a DC gate current of 0.5mA is required. In a failure case (e.g. excessive
temperature) an internal resistor of about 100
is connected between the OMNIFET's gate
and source. This state is used to detect errors by the controlling ASIC.
The control ASIC's standard application is in the use as a high side or low side switch (select-
able) in a 24V-supply system, where the functionality is guaranteed up to a maximum driver
voltage of 55V.
In the load dump case (VTR = 60V, Pulse duration about 5ms, 5 pulses) the ASIC remains
functioning (function state A) with modified parameters (rise times and fall times).
The ASIC contains one driver circuit (OMNIFET driver) and realises the following functions:
Current controlled on switch / off switch with defined rise, fall and delay times (programma-
ble externally at the control input), that is usable as a high side or low side switch.
Automatic mode change between low side and high side use. This allows processing both,
relatively low driver voltages (up to 25V, low side switch) and high driver voltages (up to
60V, high side switch) by detecting the present driver voltage related to OMNIFET's source
potential.
Error detection for the OMNIFET and generation of an error status signal.
Gate to source voltage limitation for the OMNIFET to a maximum of 13V (OMNIFET pro-
tection).
Floating ground interface between the controlling processor (control and status signal) and
the driven OMNIFET; provided by separation of digital and power ground. The OMNIFET's
source potential is the ASIC's ground.
Power reduction in the off-state (Supply current falling to less than 80A after switching the
ASIC off).
The driver can be used as low or high side switch.
The control and the fault back signal are realised with current sources in order to guarantee
the separation of digital ground (of the processor) and power ground (at the load circuit). This
is a safety function for a broken ASIC ground line and it fulfils EMC demands.
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 3 of 11
Austria Mikro Systeme International AG
In applications as a high side driver the OMNIFET's source is connected to the ASIC ground,
which switches together with the load circuit. Changes in the ASIC's ground potential of up to
58V, and rise and fall speeds of up to 58V/s are permitted.
F u n c t i o n a l D e s c r i p t i o n
Block diagram
Figure 1: Block diagram of the AS8401
Description
From the functional view the chip can be divided into the following units:
A driving circuit, which implements a current-controlled switching of the OMNIFET with current
pulses of approximately +30 mA, and makes the following further functions available:
Detection of the operating condition of the OMNIFET and generation of an error status
signal (Output of a current of approximately 0.5 mA in the event of an error)
Defined delay of the switching-on-impulse of approximately 2.0s and implementation of a
delay of the switch-off-impulse of smaller than 0.5s
Defined (current-controlled) rise/fall times of approximately. 2.0s/1,0s
Disconnection of the switching-on-impulse after approximately 5,0s and connecting a cur-
rent source of approximately 3 mA whilst the OMNIFET is switched on for the supply of the
OMNIFET's protective circuits and error recognition
Current sinking at the OMNIFET drive pin of up to 30 mA during the off state ensures a
safe off status.
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 4 of 11
Austria Mikro Systeme International AG
1. Automatic mode recognition / mode switching, which is controlled by detection of the driver
voltage VTR related to the source potential:
Operating as a low side switch (mode1), the driver voltage is approximately 10V and
the point of switching is approximately 25V.
When the AS8401 operates as a high side switch, during the transition of the OMNIFET
to conduction, provided that the ASIC's supply voltage, VTR, remains constant, the
ASIC's output current should be maintained.
2. A bandgap stabilised 5V voltage regulator, which generates the supply voltage for the
digital control section and all the voltage references
3. A floating ground interface to the controlling processor (pin IN), comprised of a reference
current supply and a general current supply, which implements the following functions:
Generation of a logic voltage signal from the ground-free input current at the pin IN
In on-state there are further derived currents for the production of the delay and rise/fall
times of the driver from the input current at the pin IN
After the OMNIFET has been switched off and an additional time delay, the control
ASIC enters power down mode. During power down the current consumption is 80A
or less. The time delay is necessary to ensure fast comparator operation in order to
complete the power down sequence.
4. A time-delayed power down circuit for the control of the generation of supply current (see
point 4)
5. Voltage delimitation which limits the voltage between gate and source of the OMNIFET to
13V
1,0V (Protection of the OMNIFET).
The ASIC controls the OMNIFET between gate and source (in particular also when it is used in
high-side-switch applications). The operating condition in which the source potential is more
positive than the gate potential, not permitted for the OMNIFET, is avoided. The use of the
source potential of the OMNIFET as ASIC ground for the ground free coupling between ASIC
and the processor causes fast variable ASIC ground potential during the switching operation
particularly when the AS8401 is used in high side switch applications.
The size of the switching-on pulses and switching-off pulses and thus the rise and fall times
with given gate-source capacities of the OMNIFET can be programmed by an external resis-
tance R
IN
, which determines the input current at the pin IN, within certain limits. The switching
time varies approximately in inverse proportion to the current I
IN
at the pin IN. Thereby it is
possible to adapt the AS8401 to the particular requirements of the OMNIFET (taking into ac-
count gate source capacitance and required delay/transition times) within certain limits (this
adjustment range is not constituent of these Device Specification). This adaptability is limited
by the possible range of the current at the input pin IN.
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 5 of 11
Austria Mikro Systeme International AG
D e f i n i t i o n o f t h e l o g i c s i g n a l s
Symbol Logic meaning
Level meaning
IN
Control input for the driver, the input
is current controlled, i.e.:
a) According to to a current from
0,1mA to DGND externally pro-
duced
b) According to no current (< 5 mA)
I
IN
= -0,1 mA
I
IN
= 0
a) appropriate driver output goes
high (according to V
OUT
= V
TR
)
b) appropriate driver output goes
low (according to V
OUT
= V
SOURCE
)
STAT Accumulated error status signal for
the controlled OMNIFET,
the output is
current controlled, i.e.:
a) fault condition according to a
current from 0,35 mA to 0.5 mA
from the ASIC to DGND
b) normally operation according to
no current
I
STAT
= -0,5mA
I
STAT
= 0
Error at the OMNIFET during the on-
status (signal is valid after termina-
tion of the switch-on procedure)
a) an error of the OMNIFET during
the on-status,
b) normal operation or off-status of
the OMNIFET
E l e c t r i c a l C h a r a c t e r i s t i c s
Absolute Maximum Ratings (Non Operating)
SYMBOL
PARAMETER
MIN
MAX
NOTE
VTR -
VPGND
DC Supply Voltage
-0.5 V
55 V
VDL
Load Dump Voltage
60V
DIN 40839 vol. 2: 5 pulse, 500ms with
Ri = 2 Ohm
I
INmax
Maximum Input Cur-
rent
-30 mA
30 mA
V
IN
< V
Inmin
respectively V
IN
> VTR
V
INA
Digital input level
VPGND -
0.3V
55V
T
strg
Storage Temperature
-55 oC
150 oC
T
sold
Soldering Temperature
260 oC
1)
t
sold
Soldering Time
10 sec
Reflow and Wave
H
Humidity
5 %
85 %
ESD
Electrostatic Discharge 1000 V
HBM: R = 1.5 k
, C = 100 pF
Note:
1) 360 oC and 3s for manual soldering
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 6 of 11
Austria Mikro Systeme International AG
Recommended Operating Conditions
The following values are valid for a temperature range from 40 to 105C and a supply voltage
range VTR from 10V to 42V. If the supply voltage VTR rises above 42V and stays below 60V
(load dump case) the circuit stay fully functional with different parameters. In every case it is
guaranteed, that the switch-off-delay is 600ns shorter than the switch-on-delay.
SYMBOL PARAMETER
MIN
TYP
MAX
NOTE
Static parameters
Driver circuit
VTR
Driver voltage
10V
42V
1)
VCC
Chip internal 5V power sup-
ply
4.7V
5.0V
5.7V
External using not allowed
I
VTRoff
Leakage current to power
ground (PGND) in the off
state
80A
VTR = 10V, Low side switch
application, off state, I
IN
= 0A,
T = 27
O
C
80A
100A
VTR = 34V, High side switch
application, off state, I
IN
= 0A,
T = 27
O
C
150A
VTR = 42V, High side switch
application, off state, I
IN
= 0A,
T = 105
O
C
I
VTRon
Current consumption in on
state
3mA
VTR = 10V, on state, I
IN
=
100A
I
OUToff
Peak switch current of the
driver in the switch-off
phase
20mA
50mA
2)
I
OUTon
Peak switch current of the
driver in the switch on-
phase
-60mA
-30mA
3)
I
OUTN
Output current of the "nor-
mal-condition" in the on-
state
0.3mA
-30mA
4)
I
OUTF
Output current of the "fault
condition" in the on-state
2mA
4mA
V
sat normal
Saturation voltage of the
"normal-condition" in the on-
state
0.5V
V
sat fault
Saturation voltage of the
"fault-condition" in the on-
state
2V
V
OUT/Source
Output voltage limitation
between OUT and SOURCE
12V
14V
5)
Control input IN
I
INon
Input current of the control
signal for the on-state
-100A
6)
I
INoff
Input current of the control
signal for the off-state
-5A
0
Status output STAT
I
STATonf
Output current of status pin
of the error case (fault con-
dition) for the on-state
-1.2mA
-0.5mA
I
STATonn
Output current of status pin
of the normal condition for
the on-state
-50A
5A
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 7 of 11
Austria Mikro Systeme International AG
Recommended Operating Conditions (continued)
SYMBOL PARAMETER
MIN
TYP
MAX
NOTE
Dynamic parameters
T
RISE
Rise time
2.4s
T
FALL
Fall time
3.8s
T
PDon
Switch on delay
0.75s
3.9s
T
PDoff
Switch off delay
4.0s
T
SP
Duration of the switch-on
current pulse
4.0s
5.0s
7.0s
Note:
1) The maximum driver voltage VTR at full function it is VTR = 42V. At VTR = 60V in the load dump case all
defined functions are staying valid (function state A). In this state it is possible that some times some parame-
ters are different from the specified value, but in every time the switch off delay is shorter then the switch on
delay.
2) Valid for an input current I
IN
= 0A. This possibility of the output OUT is valid the off state.
3) Valid for an input current I
IN
= 100A. This possibility of the output OUT is valid the on state.
4) This is the input current of the OMNIFET in the on-state
5) This is a chip internal dynamical limitation of the output voltage.
6) Correspondent with the output current of the control circuit. The capacity on the pin IN has to be low (C
PIN
extern
< 1 pF). The tolerance of this current controls the switch timing.
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 8 of 11
Austria Mikro Systeme International AG
SOIC-8
1
2
3
4
n.c.
IN
n.c.
STAT
SOURCE
VCC
OUT
VTR
AS8401
8
7
6
5
(Top view)
P i n - o u t I n f o r m a t i o n
Pin Description
Figure 2: Pin-out AS8401
Pin list
Pin No. Pin Name
Type
Description
1
n.c.
Not connected
2
IN
Input
Control input of the driver
3
n.c.
Not connected
4
STAT
Output
Output for state signal ( error state)
5
VCC
Output
Internal supply for logic (5V)
6
SOURCE
Ground Source of the OMNIFET and ground of the ASIC
7
OUT
Output
Driver output (gate of the OMNIFET)
8
VTR
Supply
Supply of the Driver
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 9 of 11
Austria Mikro Systeme International AG
A p p l i c a t i o n S c h e m a t i c
High side switch
Figure 3: AS8401/OmniFet as high-side switch
Low side switch
Figure 4: AS8401/OmniFet as low-side switch
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 10 of 11
Austria Mikro Systeme International AG
Grounding concept
In Figure 3 and 4 two possible application circuits for the AS8401/OmniFet were shown. For a
better understanding of this two application circuits in Figure 5 a Grounding/Supply-concept for
this two circuits is shown.
Figure 5: AS8401/OmniFet application circuits grounding/supply-concept
Multipurpose control ASIC for OMNINET Data Sheet
AS8401
Rev. A December 1999
Page 11 of 11
Austria Mikro Systeme International AG
P a c k a g e I n f o r m a t i o n
Package
: SOIC 8 small outline
SOIC 8
SOIC 8
small outline
Marking
(Dimensions in mm)
AS8401
Chip number
min.
nom.
max.
YY
Year of Production
A
1,6
1,6
1,7
WW
Week of Production
A1
0,1
0,15
0,3
XXX
Assembly-ID
A2
1,40
1,5
1,6
B
0,4
0,4
0,5
C
0,19
0,2
0,3
D
4,8
4,9
5
E
3,8
3,9
3,99
e
1,27 BSC
H
5,8
5,99
6,2
h
0,25
0,33
0,41
L
0,41
0,64
0,9
0
5
8
Figure 6: Physical package dimensions
Copyright
1999, Austria Mikro Systeme International AG, Schlo Premsttten, 8141 Unterpremsttten, Austria.
Telefon +43-(0)3136-500-0, Telefax +43-(0)3136-52501, E-Mail info@amsint.com
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any
means, without the prior permission in writing by the copyright holder. To the best of its knowledge, Austria Mikro Systeme International
asserts that the information contained in this publication is accurate and correct.
A1
A
h x 45
L
e
B
D
E
H
seating plane
R
2
3
4
5
6
7
A2
C
YYWWXXX
1
8
AS8401
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