
OL2068
Industrial 30 Volt 4-Channel Differential Power Line Driver - Short Circuit Proof -
Functional description
The main contents of this new CMOS power line driver are four identical blocks (systems A to D) with each a CMOS/TTL Schmitt Trigger Input and
high power differential buffered and inverted outputs.
With the low active ENABLE pin it is possible to switch off all eight outputs (high-impedance state), thus this driver can be used in industrial bus
systems.
In some rare applications it might be useful to disable the over temperature shutdown. This can be done by setting the ENABLE pin to a level
between >7,5 V and <12 V In this case the whole protection of the IC is disabled ! In case of any short circuits or thermal overdrive, the driver might
be destroyed !
An internal ultra low drop voltage regulator with typical 5.0 V supplies the internal logic to reduce power dissipation. Some applications require
additional 5V ( i.e. for an LED driver in an optical encoder). This voltage can be sourced out of the line driver internal voltage regulator ( 5mA max.).
The over-temperature protection block is placed in the center of the chip. The thermal shutdown will be activated, when a overload condition (i.e.
short circuit) has exceeded the over-temperature detection threshold.
In this case automatically all output drivers are switched off and (ET2068) an error signal is activated on a monitor pin. After the chip has cooled
down ( a few milliseconds ) it automatically re-activates all functions and switches the MON output high again. In case the short circuit is still
present, it switches off again and the same cycle starts from the beginning.
By using this line driver, the field returns of systems, which are accidentally shorted and blown by the end users, are dramatically reduced.
Power supply
The internal power supply is designed as a voltage regulator with a typical output voltage V
= 5.0 V. The minimal voltage drop across the regulator
transistors could not be lower than 0.3 V In order to decouple V
CCI
it has to be connected to an external capacitor of 100nF.
The V
pin could be used as a reference voltage for LED drivers or is able to supply other external devices like sensors at a maximum current of
I
CCIE
= 5.0 mA. Please keep in mind, that by using this voltage regulator it will generate additional power dissipation = heat.
Under-voltage reset
If the system is switched on, the status of the line driver is, for a few microseconds, undefined. The same happens, if heavy power supply failures
occur. To avoid wrong data transmitted, there is a supply voltage watchdog implemented.
The under-voltage reset block contains a comparator. The voltage V
CCI
will be always compared with a reference voltage, provided by an internal
bandgap cell.
If after a filter time (t
LVR ~ 5 s) V
drops below the typical voltage threshold of 3.5 V the output signal of this block switches off all output drivers
to the high-impedance state until minimum 3.6 V are reappearing. In case of such a system fault also the output MON generates an error signal. This
(inverted) signal can also be used as a "system ready" signal.
ESD / EMI
The chip is an ESD sensitive device and should be handled according to guideline EN100015 / part 1 (“The Protection of ESD Sensitive Devices”).
All pins are ESD protected according to ESD standard MIL883, method 3015.7 (human body model). Unused Inputs should be connected to GND,
as well as the pin ENABLE in case this function is not used. This will reduce the quiescent supply current.
Heatlink
For higher power dissipation, the part can be ordered with an added heatlink underneath the IC. This non conductive heatlink automatically gives an
excellent thermal contact to the PCB, thus the driving capability can be upgraded up to 20% more driving current. No specific user assembly routines
required - just solder the IC to your PCB and the heatlink is automatically making contact with the circuit board.
Life support clause
The schematics and in general the linedrivers are not intended for use in life support appliances, critical components or systems without the express
written consent of Optolab Microsystems GmbH. As used herein:
1
. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and
whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in
a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure
of the life support device or system, or to affect its safety or effectiveness.
For Stateside information contact...
Quantum Devices, Inc., 112 Orbison St., PO Box 100, Barneveld, WI, 53507
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Tele: (608) 924-3000
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Fax: (608) 924-3007
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URL: www.quantumdev.com
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Email: qdisales@quantumdev.com