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Features
* * * * * * * *
Wide Power Supply Voltage Range Short-circuit Protected K-interface, ISO9141 Compatible Three Short-circuit Protected 40-mA Open-collector Buffers All Low-power Outputs with Built-in 28-V Clamping CMOS Compatible Digital Inputs with Hysteresis Digital 1-mA Push-pull "RxD" K-line Output Channel-specific Over-temperature Switch Off in Event of Short Circuit Load-dump Protection and Interference Protection According to ISO 7637-1/4 (DIN 40839)
Description
The U6812B is a bipolar monolithic K-line bus transceiver designed to provide bi-directional serial communication in automotive diagnostic applications. The standard K-line is ISO 9141 compatible for baud rates up to 250 kBaud. The IC provides three universally applicable 40-mA open-collector buffers, that can be used for signal decoupling. The U6812B is manufactured using Atmel's bipolar process and fully complies to automotive industry specifications.The U6812B provides an ideal grouping of SO-packaged low-power drivers, thus meeting customers' demand for space-saving and cost-effective circuit board assembly.
Single-ended Bus Transceiver with Triple Buffer U6812B
Figure 1. Block Diagram
VS VCC
VS
K-diagnosis ISO 9141
K
VS/2
TXD
VCC
TXD
VCC/2
GND
OUT 1 IN 1
VCC/2 VCC
GND
Temperature control
IN 2
OUT 2
GND DIS OUT 3 IN 3 GND
Rev. 4760A-AUTO-10/03
Pin Configuration
Figure 2. Pinning SO16
16 15 14 13 GND K TXD RXD
GND OUT 2 IN 2 DIS VCC IN 3 OUT 3 GND
1 2 3 4
U6812B
5 6 7 8 12 VS
11 IN 1 10 OUT 1 9 GND
Pin Description
Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Symbol GND OUT 2 IN 2 DIS VCC IN 3 OUT 3 GND GND OUT 1 IN 1 VS RXD TXD K GND Type Supply Open-collector output Digital input Digital input Supply Digital input Open-collector output Supply Supply Open-collector output Digital input Supply/reference Digital output Digital input 12-V input and O.C. output Supply Function Ground; all ground pins are directly connected to the lead frame Protected output of driver 2 (faced to: outside) Input of protected driver 2 (faced to: P) Disable input for OUT 2 and OUT 3, "H"=enable, "L"=disable +5-V supply Input of protected driver 3 (faced to: P) Protected output of driver 3 (faced to: outside) Ground Ground Protected output of driver 1 (faced to: outside) Input of protected driver 1 (faced to: P) +12-V reference for K-line level Diagnosis receive line (faced to: P) Diagnosis transmit line (faced to: P) Bi-directional diagnosis line (faced to: outside) Ground
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U6812B
Figure 3. Basic Application Circuit
VBatt
D1
C1 10
+ R1 1k
K
C2
TXD RXD IN 1 OUT 1
VS
16 15 14 13 12 11 10 9
U6812B
1
2
3
4
5
6
7
8
IN 2 OUT 3 DIS OUT 2 VCC IN 3
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Functional Description
K-interface
The K-interface is equipped with a 40-mA open-collector driver. The current is determined by the external pull-up resistor. The saturation voltage is below 0.6 V. The open-collector output is protected by a 28-V Z-diode. The collector current is permanently monitored for short circuits via a built-in shunt. In the event of a short circuit occurring at VBatt, the collector current is held at approximately Icreg = 80 mA; the chip temperature then rises due to power loss. This status is maintained until the detection of overtemperature which causes the K-line output to be disabled and stored to memory. The internal short-circuit detection threshold is Isc > 0.8 Icreg. The output remains disabled until a falling edge of a pulse is available to its input. Any further attempt to connect while the short circuit is still present causes the above sequence to be repeated. The output can be activated normally once the short circuit has been removed. The maximum baud rate is 250 kBaud. The K-line allows bi-directional communication with the microcontroller. When the output K is disabled, information can be transferred to the processor via the input comparator at pin RxD. The digital output RxD is a push-pull output stage with a driver power of 1 mA. In the event of a line break at the K-line, the output K is connected to GND via the builtin 85-kW pull-down resistor, thus allowing the microcontroller to detect this fault. The maximum sampling frequency is 250 kBaud.
Open-collector Driver OUTx
The outputs are designed for a maximum static current of 40 mA, which is determined by the external pull-up resistor. The saturation voltage is below 0.6 V The three OUTx-driver outputs are activated with "active low" at the corresponding input. Outputs OUT2 and OUT3 can also be disabled with "active low" at the disable input, regardless of their input signal. The outputs are released by an open disable input or by using high potential. The open-collector outputs are connected to a 28-V Z-diode. The collector current is permanently monitored via a built-in shunt circuit to permit the detection of short circuits. If a short circuit occurs at V Batt , the collector current is held at approximately Icreg = 80 mA; accompanied with a rise of chip temperature due to power loss. This status is maintained until the detection of overtemperature which causes the output affected by the short circuit to be selectively disabled and stored to memory. The internal short-circuit detection threshold is I sc > 0.8 Icreg . The affected output remains disabled until a falling edge of a pulse is available to its input. Any further attempt to connect while the short circuit is still present causes the above sequence to be repeated. The output can be activated normally once the short circuit has been removed.
Power Supply
The IC must be equipped with external RC circuitry to limit the voltage in the event of power surges (see Figure 3 on page 3). This prevents the circuit from being damaged or destroyed, and provides a buffer in case of power fluctuations at VBatt. The RxD comparator is powered via pin VS, producing its reference voltage of 1/2 V S, while all other blocks are supplied via VCC. The operating voltage can vary between VS= 7 V and 26 V. The resistor R1 at pin VS limits the current via the built-in 28-V Z-diode between VS and GND.
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U6812B
Application Note
It is recommended to use the external components as shown in Figure 3 on page 3 with the reverse battery protection diode D1 and the buffer capacitor C1 = 10 F. The digital inputs are CMOS-compatible and equipped with a built-in pull-up resistor with a typical rating of 85 kW to VCC. The input threshold totals VTH = 0.57 VCC with a typical hysteresis of 100 mV. The inputs are designed for an input voltage of -0.2 V to VCC + 0.6 V. For proper activation of the output stages, it is mandatory that the inputs are kept low as long as the supply voltage is not applied. When the supply voltage has been applied, all inputs need to have a falling edge (see "Timing Diagrams" on page 6).
Digital Inputs (DIS, IN 1, IN 2, IN 3 and TxD)
Digital Output (RxD)
The digital output RxD is a push-pull output stage with a driver power of IRxD = 1 mA.
Interference Voltages The U6812B is protected against interference pulses (usually present in the wiring) by and Load Dump (Defined the recommended R1C1 circuitry and the integrated elements (28-V Z-diodes, both at in DIN40839 or ISO7637) the supply pin and at the output pins and two diodes connected to VCC and GND at the
digital inputs). All transient pulses, which appear on the supply line (VBatt), should not affect the function of the IC (see Table 1).
Table 1. Transient Test Conditions
Name DIN/ISO 1 DIN/ISO 2 DIN/ISO 3a DIN/ISO 3b DIN/ISO 5 Voltage -110 V 110 V -160 V 150 V 55 V (total) Source Resistance 10 W 10 W 50 W 50 W 2W Rise Time 100 V/s 100 V/s 30 V/ns 20 V/ns 10 V/ms Pulse Duration 2 ms 0.05 ms 0.1 s 0.1 s 500 ms Pulse Amount 15000 15000 1 h (reference to ISO) 1 h (reference to ISO) 20
Table 2. Truth Table
WSI-1 L H L X X X WSI-2 L H L X X X WSI-R X X X H L X EN H X L X X X TXD X X X H L X K X X X Open L H WSO-1 L Open Open X L X WSO-2 L Open Open X X X WSO-R X X X Open L X RXD X X X H L H
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Timing Diagrams
Figure 4. IN2/IN3 - Pulse Diagram
VS
IN2/IN3
DIS
OUT2/OUT3
Short 150C Temperature
140C
Figure 5. IN1 - Pulse Diagram
VS IN1
OUT1
Short 150C Temperature
140C
Figure 6. K-interface Pulse Diagram
VS
TxD
K
RxD
Short 150C Temperature
140C
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U6812B
Absolute Maximum Ratings
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Parameters Operating voltage Operating voltage Voltage at pins IN1,2,3; RxD, TxD, DIS Voltage at pins OUT1, 2, 3; K Static collector current at pins OUT1,2,3; K Ambient temperature Storage temperature range Maximum junction temperature Symbol VS VCC Vi Vo Ix Tamb Tstg Tj Value 26 3 to 6 -0.2 to +6 -1 to +26 45 -40 to +125 -55 to +150 150 Unit V V V V mA C C C
Thermal Resistance
Parameters Junction to case Junction to ambient; strongly depending on the assembly Symbol RthJC RthJA Value 36 65 to 80 Unit K/W K/W
Electrical Characteristics
Tamb = -40 to +125C, VCC = 4.75 V to 5.25 V (unless otherwise specified), reference point is GND (pin 1, 7, 8, 16). IC with recommended external components (see Figure 3 on page 3).
Parameters Supply Supply voltage Supply voltage Reduced supply voltage Vsat = 0.6 V at IX = 20 mA All inputs open or high at VCC = 5.25 V All inputs on (= low) at VCC = 5.25 V Test Conditions Pin 5, 12 VS VCC VCC IS IS R1 C1 IS = 20 mA All outputs low or open at VS = 18 V 3, 4, 6, 11, 14 Vi Ri -0.2 30 85 VCC + 0.6 170 V kW VS IVS 26 1 10 28 30 0.75 7 4.5 3.0 26 5.5 4.5 6 20 V V V mA mA kW F V mA Symbol Min. Typ. Max. Unit
Current consumption
Protective resistor Smoothing capacitor Integrated Z-diode Quiescent current
Inputs IN 1, IN 2, IN 3, DIS, TxD Input voltage Internal pull-up resistor
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Electrical Characteristics (Continued)
Tamb = -40 to +125C, VCC = 4.75 V to 5.25 V (unless otherwise specified), reference point is GND (pin 1, 7, 8, 16). IC with recommended external components (see Figure 3 on page 3).
Parameters Switchover threshold Hysteresis Outputs OUT 1, OUT 2, OUT 3 Integrated Z-diode Current regulation Saturation voltage Maximum voltage Leakage current Output RxD Integrated Z-diode Output current Saturation voltage Rise time Fall time K-line Threshold Internal pull-down resistor Integrated Z-diode Current regulation Saturation voltage Maximum voltage Maximum baud rate IK = 40 mA, C2 = 20 nF C2 = 470 pF IK = 40 mA IK = 20 mA 15 VK RK VK IK VKsat Vout -1.0 14.4 250 30 26 45 0.57 VS 85 28 170 30 130 0.6 26 V kW V mA V V kBaud kBaud IRxD = 1 mA IRxD = 20 mA Output open, VS = 21 V 13 VRxD IRxD VRxDSAT tR tF 0.01 0.01 26 28 30 1 0.5 5 5 V mA V s s IOUTx = 40 mA IOUTx = 20 mA 2, 7, 10 VO IO VOSAT Vout ILeak -1.0 26 45 28 30 130 0.6 26 2 V mA V V A Test Conditions Pin Symbol ViTH ViHYS Min. Typ. 0.57 VCC 100 Max. Unit V mV
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U6812B
Ordering Information
Extended Type Number U6812B Package SO16/150 mil Remarks -
Package Information
Package SO16
Dimensions in mm
10.0 9.85 5.2 4.8 3.7
1.4 0.4 1.27 8.89 16 9 0.25 0.10 0.2 3.8 6.15 5.85
technical drawings according to DIN specifications
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4760A-AUTO-10/03

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