MC33290D(2002) Просмотр технического описания (PDF) - Motorola => Freescale
Номер в каталоге
Компоненты Описание
производитель
MC33290D Datasheet PDF : 12 Pages
| |||
APPLICATIONS INFORMATION
INTRODUCTION
The 33290 is a serial link bus interface device conforming to
the ISO 9141 physical bus specification. The device was
designed for automotive environment usage compliant with On-
Board Diagnostic (OBD) requirements set forth by the California
Air Resources Board (CARB) using the ISO K line. The device
does not incorporate an ISO L line. It provides bi-directional
half-duplex communications interfacing from a microcontroller
to the communication bus. The 33290 incorporates circuitry to
interface the digital translations from 5.0 V microcontroller logic
levels to battery level logic and from battery level logic to 5.0 V
logic levels. The 33290 is built using Motorola’s SMARTMOS™
process and is packaged in an 8-pin plastic SOIC.
FUNCTIONAL DESCRIPTION
The 33290 transforms 5.0 V microcontroller logic signals to
battery level logic signals and visa versa. This serial link
interface device, operating in a typical automotive diagnostic
application, operates at bit rates up to 10.4 kbps with less than
2.0 ∝ s propagation delay and less than 2.0 ∝ s fall time. Rise
time is a function of the resistor used in the application to pull
up the bus to battery voltage, working in conjunction with the
total capacitance present on the bus. The serial link interface
will remain fully functional over a battery voltage range of 6.0 to
18 V. The device is parametrically specified over a dynamic VBB
voltage range of 8.0 to 18 V.
Required input levels from the microcontroller are ratio-
metric with the VDD voltage normally used to power the
microcontroller. This enhances the 33290’s ability to remain in
harmony with the RX and TX control input signals of the
microcontroller. The RX and TX control inputs are compatible
with standard 5.0 V CMOS circuitry. For fault-tolerant purposes
the TX input from the microcontroller has an internal passive
pull-up to VDD of approximately 125 kΩ, while the CEN input
has an internal passive pull-down to ground of approximately
125 kΩ.
In the receive mode, all ISO K Line bus input signals greater
than the 0.7 x VBB thresholds are valid for a high-level signal
and less than the 0.4 x VBB thresholds for a low-level signal. In
the transmit mode, valid ISO K line bus output signal levels are
greater than 0.95 x VBB and less than 0.1 x VBB. A pull-up
resistor of ≥ 100 kΩ to battery is internally provided as well as
an active data pull-down. The internal active pull-down is
current-limit-protected against shorts to battery and further
protected by thermal shutdown. Typical applications have
reverse battery protection by the incorporation of an external
510 Ω pull-up resistor and diode to battery.
Reverse battery protection of the device is provided by using
a reverse battery blocking diode [(D) in the Simplified
Application Diagram on page 1]. Battery line transient
protection of the device is provided for by using a 45 V zener
and a 500 Ω resistor connected to the VBB source as shown in
the same diagram. Device ESD protection from the
communication lines exiting the module is through the use of
the 10 nF connected to the VBB device pin and the 5.0 nF used
in conjunction with the 27 V zener connected to the ISO pin.
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33290
9
Share Link: 