High Temperature Behavior of ISL3178AE ® Application Note July 7, 2009 Description set to provide a burst mode of five pulses at a bit rate of 10Mbps.The RX device was wired up with two thermocouples one placed on the device case top and the the other placed on the PWB near the GND pin. The RX device was heated using a temperature forcing system from +25°C to +200°C. The Rx showed one threshold point. The ISL3178AE is a 3.3V based RS-485 MIL temperature rated transceiver aimed at addressing applications that require high operating temperatures. The receiver inputs A and B are presented in pins 6 and 7; when RE is low, this differential input signal is processed and available at the RO pin. The Driver input is presented at pin 4 and the driver differential outputs Z and Y are available at pins 6 and 7 respectively when DE is high. This Application Note aims at characterizing the device at temperatures from +125°C to +200°C. At a Data rate of 10Mbps: 1. The pulse width 70% threshold is at a die temp of min. = +190°C and max. = +196°C while operating at a data rate of 10Mbps. This is based on a sample size of 15pcs. and a six sigma distribution. Device Pinout TX High Temperature Test ISL3178AE (8 LD SOIC) TOP VIEW RO 1 R RE 2 DE 3 DI 4 D AN1475.0 8 VCC 7 B/Z 6 A/Y 5 GND The TX was tested using a the EVALB TX portion of Figure 2. The 200ft cable was disconnected and terminations of 100Ω and 54Ω were connected based on test requirement. The parameters tested were: Driver differential output voltage, propagation delay, and skew. The results are per the “Typical Performance Curves” on page 2. Supply Current vs High Temperature The supply current is found to have a knee at around +195°C, and increases rapidly thereafter. The supply current with (driver enabled) DE high is typically around 517µA. This value increases to about 1143.5µA at +240°C. With DE connected to GND (driver disabled) the supply current drops to about 400µA typical. The value of supply current increases from a temperature of +200°C and higher to about 605.6µA. Figure 1 shows the evaluation board schematic. The device evaluation board is common to TX and RX. The mode of operation is determined by the logic presented to the DE and RE pins. RX High Temperature Test Figure 2 shows the High temperature test setup. The board wired up as the transmitter is called the EVALB TX and the one wired the receiver is called the EVALB RX. The differential lines were hooked up through 200ft. of twisted pair cable terminated on either side by 120Ω. The VIN was set to a worst case of 4.5V. The driver input of the EVALB TX is connected to a function generator capable of providing fast rise and fall times. The function generator output was Driver Input vs High Temperature The Driver input did not latchup at a VIN = 3.0V up to +220°C. This is likely because the device VIN is below the holdoff. VCC/3.3V/PIN8 C6 10u TP3/RO/PIN1 0 U1 TP4/RE#/PIN2 1 2 3 4 TP5/DE/PIN3 TP6/DI/PIN4 RO RE DE DI VCC TX-Z / RX-B TX-Y / RX-A GND 8 7 6 5 ISL3178 C2B 0.1u 0 TP8/TX-Z/RX-B/PIN7 R10 120 TP7/TX-Y/RX-A/PIN6 GND/PIN5 R5 49.9 0 R6 49.9 0 R7 49.9 0 FIGURE 1. EVALUATION BOARD SCHEMATIC 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2009. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1475 SCOPE1/CH3 SCOPE1/CH1 SCOPE1/CH4 SCOPE1/CH2 CABLE 200ft V2 3V V3 3V VCC/3.3V/PIN8 0 TP4/RE#/PIN2 TP5/DE/PIN3 RX 0 TP4/RE#/PIN2 TP8/TX-Z/RX-B/PIN7 TP5/DE/PIN3 VCC/3.3V/PIN8 TX TP7/TX-Y/RX-A/PIN6 TP7/TX-Y/RX-A/PIN6 TP6/DI/PIN4 EVALB V1 = 0 V2 = 3 TD = 0 TR = 1ns TF = 1ns PW = 100ns PER = 200ns TP3/RO/PIN1 SCOPE1/CHx GND/PIN5 TP3/RO/PIN1 GND/PIN5 TP6/DI/PIN4 TP8/TX-Z/RX-B/PIN7 EVALB V1 0 0 0 SCOPE1/CHx FIGURE 2. HIGH TEMPERATURE SETUP 2.9 2.7 2.5 RDIFF = 100Ω 2.3 2.1 1.9 RDIFF = 54Ω 1.7 -55 0 55 110 165 1.5 220 DIFFERENTIAL OUTPUT VOLTAGE (V) Typical Performance Curves TEMPERATURE (°C) FIGURE 3. TPLH AND TPHL AT A DIE TEMPERATURE OF +231°C 2 FIGURE 4. DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs TEMPERATURE AN1475.0 July 7, 2009 Application Note 1475 Typical Performance Curves (Continued) 60 50 ICC DE-VCC 45 ICC (µA) 55 40 ICC DE-GND -55 FIGURE 5. COMPRESSED TIMESCALE TO SHOW RINGING AT THE RX INPUT AT +202°C 0 55 11 TEMPERATURE (°C) 165 FIGURE 6. SUPPLY CURRENT vs TEMPERATURE 45 35 30 25 tPLH 20 15 10 5 -55 0 55 110 165 0 220 TEMPERATURE (°C) FIGURE 7. DRIVER DIFFERENTIAL PROPAGATION DELAY vs TEMPERATURE FIGURE 9. TX/RX WAVEFORM AT +194.2°C TYP, 10Mbps AND VIN = 3.0V 1.5 1.4 1.3 1.2 SKEW (ns) tPHL 1.6 PROPOGATION DELAY (ns) 40 35 22 SKEW 1.1 -55 0 55 110 165 1.0 22 TEMPERATURE (°C) FIGURE 8. DRIVER DIFFERENTIAL SKEW vs TEMPERATURE FIGURE 10. TX/RX WAVEFORM AT +194.2°C TYP, 10Mbps AND VIN = 3.0V Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 3 AN1475.0 July 7, 2009