Octal Port Protecton

www.DataSheet4U.com DA9171A.000 July 31, 1997 MAS9171A OCTAL PORT PROTECTON • Parallel In, Parallel Out • High Voltage Inputs • Automotive DESCRIPTION The MAS9171A is an eight channel protection circuit for microprocessors in automotive applications. All inputs are protected against energy rich pulses according to DIN40839/ISO7637. Internal analog filters and suitable input threshold voltages provide the functionality within a noise spectrum of 150 kHz up to 1 GHz without need of external filter components. The MAS9171A is optimized for low current consumption. FEATURES • • • • • • • 8 digital channels Supply voltage 3.3 V/5 V Low supply current High voltage inputs Internal analog filter -40°C to +125°C SO-18 package APPLICATION • Replacement of protection circuitry in car electronics and industrial bus systems BLOCK DIAGRAM VDD IN1 IN2 IN3 IN4 IN5 IN6 IN7 IN8 OUT1 OUT2 OUT3 OUT4 PROTECT FILTER COMP OUT5 OUT6 OUT7 OUT8 GND 1 www.DataSheet4U.com DA9171A.000 July 31, 1997 PIN CONFIGURATION PIN DESCRIPTION Pin Name GND IN1 IN2 IN3 IN4 IN5 IN6 IN7 IN8 OUT8 OUT7 OUT6 OUT5 OUT4 OUT3 OUT2 OUT1 VDD Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Type G I I I I I I I I O O O O O O O O P Function Ground Digital Input 1 Digital Input 2 Digital Input 3 Digital Input 4 Digital Input 5 Digital Input 6 Digital Input 7 Digital Input 8 Digital Output 8 Digital Output 7 Digital Output 6 Digital Output 5 Digital Output 4 Digital Output 3 Digital Output 2 Digital Output 1 Positive Supply Voltage ¨'!$¥ &% # 0 ¨'!$¥ &% # ¥ ¨'!$¥ &% # © '!#)(¥ &%  '!#)(¥ &%  '!#)(¥ &%  ©¨'!$¥ &% #  ¥ &% #  ¨'!$¥ £ £  "! ¥ © 2  ¨ §¡   ¨ §¡   ¨ §¡    §¡    §¡    §¡   ¨ §¡ © ¥ ¨ §¡ ¥ £ ¡ ¦¤¢  www.DataSheet4U.com DA9171A.000 July 31, 1997 ABSOLUTE MAXIMUM RATINGS Parameter Supply Voltage Input Voltage ESD Voltage Output Current (Note 1) Ambient Temperature Storage Temperature Symbol VDD VIN IOUT Tamb TStg Conditions T = 125°C, f=100Hz, 5% On MM (EIAJ ED-4701 Method C-111) T=125°C Min -0.5 -200 -500 -40 -55 Max 7 200 500 5 +125 +150 Unit V V V mA o C o C RECOMMENDED OPERATION CONDITIONS Parameter Supply Voltage Supply Current Symbol VDD IDD VDD = 5.0 V VIN 1…8 = 0 V Conditions Min 3.3 Typ 5.0 3nA Max 5.5 10 Unit V µA ELECTRICAL CHARACTERISTICS x Parallel input port (T=-40°C .. +125°C, VDD = 3.3V..5.5V) Parameter Input High Voltage (Note 2) Input Low Voltage (Note 2) DC Input Voltage Input Resistance 3 dB Frequency of Analog Filter x Parallel digital outputs Symbol VIH VIL Vmax RIN1 fd Conditions VDD = 5.0 V VDD = 5.0 V Only 1 input at the same time -1V 5.5 V and “Low” if VINx < 2.75 V (typical values). 100 K IN 1….8 1K 125 K to Comparator 6.8V 125 K 6.8V 9pF 4pF Fig 1.: Input Channel of MAS9171A 4 www.DataSheet4U.com DA9171A.000 July 31, 1997 APPLICATION INFORMATION • GENERAL In the late 70ties microcontrollers have been introduced into most of the low cost applications in the field of consumer, industrial and automotive. Lowest cost 8-Bit microcontrollers are used in modern computer monitors for user programmable adjustment of the picture geometrie. A modern car can carry up to 40 microcontrollers that control motor managment, air condition, wipers, brakes, instruments,...... The increased density of complex electronic systems results in high electromagnetic fields with a wide frequency spectrum in the environment. Examples for typical noise sources are DC-Motors, ignitors, discharge lamps, switch-mode supplies and all different kinds of transmitters like mobile phones and radio stations. The requirements on EMI immunity are defined in several DIN, ISO and IEC standards. Design-Engineers have to think of how to protect sensitive components like microcontrollers against overvoltage pulses. Especially pulses with short rise times might cause problems because most of the standard components are not designed to work properly at frequencies above the cut-off frequency. In addition the layout of the PCB is very critical at high frequencies. Filters components have to be placed very closely to the connectors leading to external wires that may work as antennas. It is quite common that a lot of filter and protection components have to be designed in at a very late phase of the project when starting EMI measurements with pre-production parts. This can cause delays to the product introduction phase and therefore it is very important to think about the limits of sensitive components already with the first Prototypes. • INPUT PROTECTION FOR MICROCONTROLLERS A typical protection circuit for a digital input of a V dd HCMOS microcontrollers consists of one series resistor, one or two block capacitors to Vss and V in two clamping diodes to Vss/Vdd. P 1 The series resistor shall limit the maximum current into the internal protection diodes to a value below the latch-up current of the input structure (typ. 25mA). Together with the capacitor it builds up a 1th order RC-filter.The purpose of the filter is to get a stable signal within the sampling period of the microcontroller without need of software filtering. For resistor values > 100 kOhms however, the Fig.2 : Discrete protection circuit leakage current of the port may cause unwanted dropout voltage which is not any longer neglectible to the input voltage. Over the full temperature and supply voltage range this can cause severe tolerance problems. Those inputs need extra clamping diodes to the Vss/Vdd and a lower value series resistor. Most of 0805/1204 SMD resistors are specified for voltages < 200V. For higher voltages two resistors in series are recommended. Especially for applications with a lot of input ports the protection circuitry around the microcontroller consumes a big amount of board space and therefore makes the board layout very difficult even when using SMD components. Each component is a potential source of an error in production and must be tested with In-circuit testers. uC 5 www.DataSheet4U.com DA9171A.000 July 31, 1997 APPLICATION INFORMATION • INPUT PROTECTION USING MAS9171A The MAS9171A is a eight channel protection circuit for microprocessors in automotive applications that may be used in industrial applications as well. All inputs are protected against energy rich pulses according to DIN40839/ISO7637. Internal analog filters and suitable input threshold voltages provide the functionality within a noise spectrum of 150KHz up to 1GHz without need of external filter components. The MAS9171A is optimized for low current consumption. Advantages of MAS9171A VDD VIN1 VIN2 VIN3 VIN4 VIN5 VIN6 VIN7 VIN8 VOUT1 VOUT2 VOUT3 Protect VOUT4 Filter COMP VOUT5 VOUT6 VOUT7 VOUT8 - lower price when comparing Part+Board costs - easy layout - better reliability - less test time - universal to use, less development time GND Fig. 3: Block diagram of MAS9171A • APPLICATION EXAMPLES VBAT Sensors Oil Switch 1 Generator Batt. Tacho Vdd Vbat MAS9171 Port2 0-12V PGND Vdd Res MAS9171 Port1 Instrument Driver Vdd Filter+ Protection VoltageRegulator + Reset Vbat uC Lamp Driver Vdd MAS9171 ABS Port3 EEPROM Fig.4: Electronic Dashboard for Cars 6 www.DataSheet4U.com DA9171A.000 July 31, 1997 APPLICATION INFORMATION Fig. 5 shows how to use the MAS9171A to detect the condition of switches V Bat V Ignition Filter+ Protection VoltageRegulator +Reset Vdd Vdd Res Vdd 4x47K MAS9171 4x47K Fig. 5: Application Circuit (Detection of Switches) IMPORTANT ! • The MAS9171A shall be placed closely to the microprocessor to avoid voltage spikes at the uC inputs caused by currents on the Supply Pins and/or Pins OUT1 to OUT8. • A block capacitor of 33nF close to the Supply Pins is recommended • It is important to connect external Pull-Up resistors to Vignition in order to prevent quiescent current int