Datasheet AS8401 Datasheet (Austria Mikro Systeme International)

AS8401

Austria Mikro Systeme International AG

Multipurpose control ASIC
for OMNIFET

Data Sheet

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

Key Features

• 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

General Description

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 limita­tion, 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 100Ω 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 (select­able) 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 80µA 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.

Rev. A December 1999 Page 2 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

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/µs are permitted.

Functional Description

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 2.0µs and implementation of a
delay of the switch-off-impulse of smaller than 0.5µs

• Defined (current-controlled) rise/fall times of approximately. 2.0µs/1,0µs

• Disconnection of the switching-on-impulse after approximately 5,0µs 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.

Rev. A December 1999 Page 3 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

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 80µA
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 resis­tance RIN, which determines the input current at the pin IN, within certain limits. The switching
time varies approximately in inverse proportion to the current IIN at the pin IN. Thereby it is
possible to adapt the AS8401 to the particular requirements of the OMNIFET (taking into ac­count 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.

Rev. A December 1999 Page 4 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

OUT

SOURCE

STAT

AS8401

Definition of the logic signals

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 pro­duced

b) According to no current (< 5 mA)

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

IIN= -0,1 mA

IIN = 0

I

= -0,5mA

I

= 0

STAT

Ü

a) appropriate driver output goes

high (according to V

OUT

= VTR)

Ü

b) appropriate driver output goes

low (according to V

= V
Error at the OMNIFET during the on­status (signal is valid after termina­tion of the switch-on procedure)

Ü

a) an error of the OMNIFET during

the on-status,

Ü

b) normal operation or off-status of

the OMNIFET

)

Electrical Characteristics

Absolute Maximum Ratings (Non Operating)

SYMBOL PARAMETER MIN MAX NOTE
VTR ­VPGND
VDL Load Dump Voltage 60V DIN 40839 vol. 2: 5 pulse, 500ms with

I

INmax

V

INA

T

strg

T

sold

t

sold

H Humidity 5 % 85 %
ESD Electrostatic Discharge 1000 V

Note:

1) 360 oC and 3s for manual soldering

DC Supply Voltage -0.5 V 55 V

Ri = 2 Ohm

Maximum Input Cur-

-30 mA 30 mA VIN < V

respectively VIN > VTR

Inmin

rent
Digital input level VPGND -

55V

0.3V

Storage Temperature
Soldering Temperature

-55 oC 150 oC
260 oC

1)

Soldering Time 10 sec Reflow and Wave

HBM: R = 1.5 kΩ, C = 100 pF

Rev. A December 1999 Page 5 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

IN

IN

IN

OUT/Source

AS8401

Recommended Operating Conditions

The following values are valid for a temperature range from –40 to 105°C 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
VCC Chip internal 5V power sup-

4.7V 5.0V 5.7V External using not allowed

ply

I

VTRoff

Leakage current to power

80µA VTR = 10V, Low side switch
ground (PGND) in the off
state

80µA 100µA VTR = 34V, High side switch

150µA VTR = 42V, High side switch

I

VTRon

Current consumption in on

3mA VTR = 10V, on state, I
state

1)

application, off state, I
T = 27OC

application, off state, I
T = 27OC

application, off state, I
T = 105OC

100µA

= 0A,

= 0A,

= 0A,

IN

=

I

OUToff

Peak switch current of the
driver in the switch-off
phase

I

OUTon

Peak switch current of the
driver in the switch on­phase

I

OUTN

Output current of the “nor­mal-condition“ in the on­state

I

OUTF

Output current of the “fault
condition“ in the on-state

V

sat normal

Saturation voltage of the
“normal-condition“ in the on­state

V

sat fault

Saturation voltage of the
“fault-condition“ in the on­state

V

Output voltage limitation
between OUT and SOURCE

Control input IN

I

INon

Input current of the control
signal for the on-state

I

INoff

Input current of the control
signal for the off-state

Status output STAT

I

STATonf

Output current of status pin
of the error case (fault con­dition) for the on-state

I

STATonn

Output current of status pin
of the normal condition for
the on-state

20mA 50mA

-60mA -30mA

0.3mA -30mA

2mA 4mA

0.5V

2V

12V 14V

-100µA

-5µA 0

-1.2mA -0.5mA

-50µA 5µA

2)

3)

4)

5)

6)

Rev. A December 1999 Page 6 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

Recommended Operating Conditions (continued)

SYMBOL PARAMETER MIN TYP MAX NOTE

Dynamic parameters

T

RISE

T

FALL

T

PDon

T

PDoff

T

SP

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 parame­ters 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

3) Valid for an input current I

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
< 1 pF). The tolerance of this current controls the switch timing.

Rise time 2.4µs
Fall time 3.8µs
Switch on delay 0.75µs 3.9µs
Switch off delay 4.0µs
Duration of the switch-on

4.0µs 5.0µs 7.0µs

current pulse

= 0A. This possibility of the output OUT is valid the off state.

IN

= 100µA. This possibility of the output OUT is valid the on state.

IN

PIN extern

Rev. A December 1999 Page 7 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

Pin-out Information

Pin Description

n.c.

n.c.

STAT

IN

1
2
3
4

AS 8401

8
7
6
5

VTR
OUT
SOURCE
VCC

SOIC-8

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

(Top view)

Rev. A December 1999 Page 8 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

Application Schematic

High side switch

Figure 3: AS8401/OmniFet as high-side switch

Low side switch

Figure 4: AS8401/OmniFet as low-side switch

Rev. A December 1999 Page 9 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

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

Rev. A December 1999 Page 10 of 11

Multipurpose control ASIC for OMNINET – Data Sheet

Austria Mikro Systeme International AG

AS8401

Package Information

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

α

0° 5° 8°

A

A2

α

A1

seating plane

h x 45°

C

L

5

R

6

7

AS8401

4

3

2

B

D

e

YYWWXXX

8

E
H

1

Figure 6: Physical package dimensions

Copyright  1999, Austria Mikro Systeme International AG, Schloß Premstätten, 8141 Unterpremstätten, Austria.
Telefon [phone], Telefax [phone], E-Mail [e-mail]
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any
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asserts that the information contained in this publication is accurate and correct.

Rev. A December 1999 Page 11 of 11