33290

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^TMprocess 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 ratiometric with the V_DD voltage normally used to power the microcontroller. This enhances the 33290’s ability to remain in harmony with the R_X and T_X control input signals of the microcontroller. The R_X and T_X control inputs are compatible with standard 5.0 V CMOS circuitry. For fault-tolerant purposes the T_X input from the microcontroller has an internal passive pull-up to V_DD of approximately 125 k, while the CEN input has an internal passive pull-down to ground of approximately 125 k.

In the receive mode, all ISO K Line bus input signals greater than the 0.7 x V_BB thresholds are valid for a high-level signal and less than the 0.4 x V_BB thresholds for a low-level signal. In the transmit mode, valid ISO K line bus output signal levels are greater than 0.95 x V_BB and less than 0.1 x V_BB. A pull-up resistor of 100 k 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 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 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.

Notes
2. Device will survive double battery jump start conditions in typical applications for 10 minutes duration, but is not guaranteed to remain within specified parametric limits during this duration.
3. ESD data available upon request.
4. ESD1 testing is performed in accordance with the Human Body Model (C_ZAP = 100 pF, R_ZAP = 1500 ).
5. ESD2 testing is performed in accordance with the Machine Model (C_ZAP = 200 pF, R_ZAP = 0 ).
6. Nonrepetitive clamping capability at 25°C.
7. Lead soldering temperature limit is for 10 seconds maximum duration. Contact Motorola Sales Office for device immersion soldering time/temperature limits.

The 33290 is a serial link bus interface device designed to provide bidirectional half-duplex communication interfacing in automotive diagnostic applications. It is designed to interface between the vehicle's on-board microcontroller and systems off-board the vehicle via the special ISO K line.The 33290 is designed to meet the Diagnostic Systems ISO9141 specification.The device's K line bus driver's output is fully protected against bus shorts and overtemperature conditions.

The 33290 derives its robustness to temperature and voltage extremes by being built on a SMARTMOS process, incorporating CMOS logic, bipolar/MOS analog circuitry, and DMOS power FETs. Although the 33290 was principally designed for automotive applications, it is suited for other serial communication applications. It is parametrically specified over an ambient temperature range of -40°C T_A 125°C and 8.0 V V_BB 18 V supply. The economical SO-8 surface-mount plastic package makes the 33290 very cost effective.