33990_06

Freescale Semiconductor Advance Information Document Number: MC33990 Rev 3.0, 11/2006 Enhanced Class B Serial Transceiver The 33990 is a serial transceiver designed to provide bi-directional half-duplex communication meeting the automotive SAE Standard J1850 Class B Data Communication Network Interface specification. It is designed to interface directly to on-board vehicle microcontrollers and serves to transmit and receive data on a single-wire bus at data rates of 10.4 kbps using Variable Pulse Width Modulation (VPWM). The 33990 operates directly from a vehicle's 12 V battery system and functions in a true logic fashion as an I/O interface between the microcontroller's 5.0 V CMOS logic level swings and the required 0 V to 7.0 V waveshaped signal swings of the bus. The bus output driver is short circuit current limited. Features • Designed for SAE J-1850 Class B Data Rates • Full Operational Bus Dynamics Over a Supply Voltage of 9.0 V to 16 V • Ambient Operating Temperature of -40°C to 125°C • Interfaces Directly to Standard 5.0 V CMOS Microcontroller • BUS Pin Protected Against Shorts to Battery and Ground • Thermal Shutdown with Hysteresis • Voltage Waveshaping of Bus Output Driver • Internally Reverse Battery Protected • 40 V Max VBAT Capability • Pb-Free Packaging Designated by Suffix Code EF 33990 J-1850 SERIAL TRANSCEIVER D SUFFIX EF SUFFIX (PB-FREE) 98ASB42564B 8-PIN SOICN ORDERING INFORMATION Device MC33990D/DR2 -40°C to 125°C MCZ33990EF/R2 8 SOICNN Temperature Range (TA) Package VBAT +VBAT 33990 Primary Node BUS SLEEP TX MCU RX LOAD Secondary Nodes GND 4X/LOOP Figure 1. 33990 Simplified Application Diagram * This document contains certain information on a new product. Specifications and information herein are subject to change without notice. © Freescale Semiconductor, Inc., 2006. All rights reserved. INTERNAL BLOCK DIAGRAM INTERNAL BLOCK DIAGRAM 33990 Bus Driver Voltage Regulator Thermal Shutdown VBAT SLEEP BUS 4.5 V Reference Waveshaping Filter Digital Output Driver 4X Enable Loopback TX RX Loss of Ground Protection LOAD 4X/LOOP GND Note This device contains approximately 400 active transistors and 250 gates. Figure 2. 33990 Simplified Internal Block Diagram 33990 2 Analog Integrated Circuit Device Data Freescale Semiconductor PIN CONNECTIONS PIN CONNECTIONS SLEEP GND LOAD BUS 1 1 2 2 3 3 4 4 88 77 66 55 RX TX 4X/LOOP VBAT Figure 3. 33990 Pin Connections Table 1. 33990 Pin Definitions Pin Number 1 2 3 4 5 6 7 8 Pin Name SLEEP GND LOAD BUS VBAT 4X/ LOOP TX RX Definition Enables the transceiver when Logic 1 and disables the transceiver when Logic 0. Device ground pin. Accommodates an external pull-down resistor to ground to provide loss of ground protection. Waveshaped SAE Standard J-1850 Class B transmitter output and receiver input. Provides device operating input power. Tristate input mode control; Logic 0 = normal waveshaping, Logic 1 = waveshaping disabled for 4X transmitting, high impedance = loopback mode. Serial data input (DI) from the microcontroller to be transmitted onto Bus. Bus received serial data output (DO) sent to the microcontroller. 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 3 ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings All voltages are with respect to ground unless otherwise noted. Rating VBAT DC Supply Voltage Input I/O Pins (2) (1) Symbol VBAT VI/O(CPU) VBUS VESD1 VESD2 TSTG TA TJ (5) (6) Value -16 to 40 -0.3 to 7.0 -2.0 to 16 Unit V V V V BUS and LOAD Outputs ESD Voltage Human Body Model (3) Machine Model (4) Storage Temperature Operating Ambient Temperature Operating Junction Temperature Peak Package Reflow Temperature During Reflow Thermal Resistance (Junction-to-Ambient) , ±2000 ±200 -65 to 150 -40 to 125 -40 to 150 Note 6. 180 °C °C °C °C °C / W TPPRT RθJ-A Notes 1. An external series diode must be used to provide reverse battery protection of the device. 2. SLEEP, TX, RX, and 4X / LOOP are normally connected to a microcontroller. 3. ESD1 testing is performed in accordance with the Human Body Model (CZAP = 100 pF, RZAP = 1500 Ω). 4. 5. 6. ESD2 testing is performed in accordance with the Machine Model (CZAP = 200 pF, RZAP = 0 Ω). Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may cause malfunction or permanent damage to the device. Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package Reflow Temperature and Moisture Sensitivity Levels (MSL), Go to www.freescale.com, search by part number [e.g. remove prefixes/suffixes and enter the core ID to view all orderable parts. (i.e. MC33xxxD enter 33xxx), and review parametrics. 33990 4 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions of 7.0 V ≤ VBAT ≤ 16 V, -40°C ≤ TA ≤ 125°C, SLEEP = 5.0 V unless otherwise noted. Typical values reflect the parameter's approximate midpoint average value with VBAT = 13 V, TA = 25°C. All positive currents are into the pin. All negative currents are out of the pin. Characteristic POWER CONSUMPTION Operational Battery Current (RMS with Tx = 7.812 kHz Square Wave) BUS Load = 1380 Ω to GND, 3.6 nF to GND BUS Load = 257 Ω to GND, 20.2 nF to GND Battery Bus Low Input Current After SLEEP Toggle Low to High; Prior to Tx Toggling After Tx Toggle High to Low Sleep State Battery Current VSLEEP = 0 V BUS BUS Input Receiver Threshold (7) Threshold High (Bus Increasing until Rx ≥ 3.0 V) Threshold Low (Bus Decreasing until Rx ≤ 3.0 V) Threshold in Sleep State (SLEEP = 0 V) Hysteresis (VBUS(IH) - VBUS(IL), SLEEP = 0 V) BUS-Out Voltage (Tx = 5.0 V, 257 Ω ≤ RBUS(L) to GND ≤ 1380 Ω) 8.2 V ≤ VBAT ≤ 16 V 4.25 V ≤ VBAT ≤ 8.2 V Tx = 0 V BUS Short Circuit Output Current Tx = 5.0 V, -2.0 V ≤ VBUS ≤ 4.8 V BUS Leakage Current -2.0 V ≤ VBUS ≤ 0 V (≥ 2.0 ms after Tx Falls to 0 V) 0 V ≤ VBUS ≤ VBAT 0 V ≤ VBUS ≤ 8.0 V BUS Thermal Shutdown (8) (Tx = 5.0 V, IBUS = -0.1 mA) Increase Temperature until VBUS ≤ 2.5 V BUS Thermal Shutdown Hysteresis (9) TBUS (LIM) - TBUS (REEN) LOAD Input Current with Loss of Ground VLOAD = -18 V (see Figure 4) BUS Input Current with Loss of Ground VBUS = -18 V (see Figure 4) IBUS (LOG) -1.0 – 0.1 ILOAD (LOG) -1.0 – 0.1 mA TBUS (LI MHYS) 10 12 15 mA IBUS (LEAK1) IBUS (LEAK2) IBUS (LEAK3) TBUS (LIM) 150 170 190 °C -0.5 -0.5 – -0.055 0.5 0.25 0.5 1.0 0.5 °C VBUS (OUT1) VBUS (OUT2) VBUS (OUT3) IBUS (SHORT) 60 129 170 mA 6.25 VBAT - 1.6 – 6.9 – 0.27 8.0 VBAT 0.7 mA VBUS(IH) VBUS(IL) BUSTH(SLEEP) VBUS(HYST) 4.25 – 2.4 0.1 3.9 3.7 3.0 0.2 – 3.5 3.4 0.6 V V IBAT(BUS L1) IBAT(BUS L2) IBAT(SLEEP) – 38.2 65 – – 1.1 6.4 3.0 8.5 µA IBAT (OP1) IBAT (OP2) – – 3.0 22.4 11.5 32 mA mA Symbol Min Typ Max Unit Notes 7. Typical threshold value is the approximate actual occurring switch point value with VBAT = 13 V, TA = 25°C. 8. 9. Device characterized but not production tested for thermal shutdown. Device characterized but not production tested for thermal shutdown hysteresis. 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 5 ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 4. Static Electrical Characteristics (continued) Characteristics noted under conditions of 7.0 V ≤ VBAT ≤ 16 V, -40°C ≤ TA ≤ 125°C, SLEEP = 5.0 V unless otherwise noted. Typical values reflect the parameter's approximate midpoint average value with VBAT = 13 V, TA = 25°C. All positive currents are into the pin. All negative currents are out of the pin. Characteristic BUS (CONTINUED) BUS Input Current with Loss of VBAT VBUS = 9.0 V (see Figure 5) LOAD Output IL = 6.0 mA Unpowered LOAD Output VBAT = 0 V, IL = 6.0 mA TX TX Input Voltage VBUS ≤ 3.875 V VBUS ≥ 3.875 V TX Input Current VTx = 5.0 V VTx = 0 V LOOP 4X / LOOP Input Current V4X / LOOP = 0 V (Normal Mode) V4X / LOOP = 5.0 V (4X Mode) 4X / LOOP Input Threshold (Tx = 4096 Hz square wave) Normal Mode to Loopback Mode Loopback Mode to 4X Mode RX RX Output Voltage Low VBUS = 0 V, IRx = 1.6 mA RX Output Voltage High VBUS = 7.0 V, IRx = -200 µA RX Output Current VRx = High; Short Circuit Protection Limits RX Sleep State Output Voltage SLEEP = 0 V, 0 ≤ VBUS ≤ 7.0 V SLEEP Input Current Symbol Min Typ Max Unit IBUS (LOB) – LON – LDIO 0.3 0.67 0.9 0.07 0.2 – 0.5 mA V V V VTx(IL) VTx(IH) – 3.5 2.27 2.27 0.8 – µA ITx(IH) ITx(IL) 50 -2.0 120 -0.1 200 2.0 µA I4X / LOOP(IL) I4X / LOOP(IH) -200 – -95 95 – 200 V V4X / LOOP(IL) V4X / LOOP(IH) 1.4 3.2 1.6 3.43 1.8 3.6 VRx (LOW) 0.01 VRx(HIGH) 4.25 IRx 2.0 VRx 4.25 4.56 4.85 5.9 8.0 4.48 4.75 0.18 0.4 V V mA V µA ISLEEP (IL) ISLEEP (IH) – 1.0 -0.003 9.5 -2.0 20 VSLEEP = 0 V VSLEEP = 5.0 V 33990 6 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS Table 5. Dynamic Electrical Characteristics Characteristics noted under conditions of 7.0 V ≤ VBAT ≤ 16 V, -40°C ≤ TA ≤ 125°C, SLEEP = 5.0 V unless otherwise noted. Typical values reflect the parameter's approximate midpoint average value with VBAT = 13 V, TA = 25°C. All positive currents are into the pin. All negative currents are out of the pin. Characteristic BUS BUS Voltage Rise Time (10) (9.0 V ≤ VBAT ≤ 16 V, Tx = 7.812 kHz Square Wave) (see Figure 6) BUS Load = 3,300 pF and 1.38 kΩ to GND BUS Load = 16,500 pF and 300 Ω to GND BUS Voltage Fall Time Wave) (see Figure 6) (10) Symbol Min Typ Max Unit trise (BUS) 9.0 9.0 tfall (BUS) 9.0 9.0 tpwd (BUS) 35 tpd (BUS) – 17.7 25 62 93 10.50 11.17 15 15 11.15 11.86 15 15 µs (9.0 V ≤ VBAT ≤ 16 V, Tx = 7.812 kHz Square µs BUS Load = 3,300 pF and 1.38 kΩ to GND BUS Load = 16,500 pF and 300 Ω to GND Pulse Width Distortion Time (9.0 V ≤ VBAT ≤ 16 V, Tx = 7.812 kHz Square Wave) (see Figure 7) BUS Load = 3,300 pF and 1.38 kΩ to GND Propagation Delay TX Threshold to RX Threshold TX TX to BUS Delay Time (Tx = 2.5 V to VBUS = 3.875 V) (Figure 8) 4X Mode Normal Mode SLEEP to Tx Setup Time (Figure 8) µs µs tTxDelay – 13 tSLEEPTxSU 80 2.6 17.3 40 4.0 24 – µs µs RX RX Output Delay Time (TX = 2.5 V to VBUS = 3.875 V) (see Figure 9) Low-to-Output High High-to-Output Low RX Output Transition Time (CRx = 50 pF to GND, 10% and 90% Points) (see Figure 10) Low-to-Output High High-to-Output Low Rx Output Transition Time 90% Points) (see Figure 10) Low-to-Output High High-to-Output Low (11) µs tRxDelay / L–H tRxDelay / H–L – – 0.11 0.38 2.0 2.0 µs tRxTrans / L–H tRxTrans /H–L – – 0.34 0.08 1.0 1.0 µs tRxTrans / L–H tRxTrans /H–L – – 0.32 0.08 5.0 5.0 (CRx = 50 pF to GND, SLEEP = 0 V, 10% and Notes 10. Typical is the parameter's approximate average value with VBAT = 13 V, TA = 25°C. 11. RX Output Transition Time from a sleep state. 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 7 ELECTRICAL CHARACTERISTICS ELECTRICAL PERFORMANCE CURVES ELECTRICAL PERFORMANCE CURVES TEST FIGURES 5.0 V Tx 33990 IBUS (LOG) VBAT BUS -18 V tpwd(min) tpwd Floating GND LOAD ILOAD (LOG) 1.5 V tpwd(max) 0V 64 µs Figure 4. Loss of Ground Test Circuit Figure 7. Pulse Width Distortion 33990 IBUS (LOB) VBAT Floating Tx GND BUS tTxDelay 3.875 V tSLEEPTxSU 2.5 V BUS 9.0 V SLEEP 2.5 V Figure 5. Loss of VBAT Test Circuit Figure 8. SLEEP to Tx Delay Times 3.5 V Tx 0.8 V 64 µs BUS 122 µs tRxDelay / lowto-output high 3.875 V 80% BUS 20% t rise t fall Rx tRxDelay /high-tooutput low 2.5 V Figure 6. BUS Rise and Fall Times Figure 9. BUS-to-Rx Delay Time 33990 8 Analog Integrated Circuit Device Data Freescale Semiconductor ELECTRICAL CHARACTERISTICS TEST FIGURES tRxTrans / L–H tRxTrans / H–L 90% Rx 10% 90% 10% Figure 10. Rx Rise and Fall Time 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 9 FUNCTIONAL DESCRIPTION INTRODUCTION FUNCTIONAL DESCRIPTION INTRODUCTION The 33990 is a serial transceiver device designed to meet the SAE Standard J-1850 Class B performance for bidirectional half-duplex communication. The device is packaged in an economical surface-mount SOIC plastic package. An internal block diagram of the device is shown in Figure 2. The 33990 derives its robustness to temperature and voltage extremes from being built on a SMARTMOS process, incorporating CMOS logic, bipolar/MOS analog circuitry, and DMOS power FETs. Though the 33990 was principally designed for automotive applications requiring SAE J-1850 Class B standards, it is suited for other serial communication applications. It is parametrically specified over an ambient temperature range of -40°C ≤ TA ≤ 125°C and 7.0 V ≤ VBAT ≤ 16 V supply. The economical 8-pin SOICN surface mount plastic package makes the device a cost-effective solution. FUNCTIONAL PIN DESCRIPTION Input Power (VBAT Pin) This is the only required input power source necessary to operate the 33990. The internal voltage reference of the 33990 will remain fully operational with a minimum of 9.0 V on this pin. Bus transmissions can continue with battery voltages down to 5.0 V. The bus output voltage will follow the battery voltage down and, in doing so, track approximately 1.6 V below the battery voltage. The device will continue to receive and transmit bus data to the microcontroller with battery voltages as low as 4.25 V. The pin can withstand voltages from -16 V to 40 V. 1.5 kΩ ± 5% pull-down resistor to ground. With more than 26 nodes, there is no primary node (see Figure 13). All nodes will have a 470 ± 10% pF capacitor and a 10.6 kΩ ± 5% pulldown resistor. No matter how many secondary nodes are on the Class B bus, the RC time constant of the Class B bus is maintained at approximately 5.0 µs. The minimum and maximum capacitance and resistance on the Class B bus is given by the expressions shown in Table 6. One Primary Node Sleep Input (SLEEP Pin) This input is used to enable and disable the Class B transmitter. The Class B receiver is always enabled so long as adequate VBAT pin voltage is applied. When the SLEEP pin voltage is 5.0 V, the Class B transmitter is enabled. If this input is logic low, the Class B transmitter will be disabled and less than 65 µA of current will be drawn by the VBAT pin. The pin also provides a 5.0 V reference, internal to the device, used to establish the Rx output level and slew rate times. 10.6 kΩ 470 pF 1.5 kΩ 3300 pF Figure 11. Minimum Bus Load Primary Node Class B Functional Description The transmitter provides an analog waveshaped 0 V to 7.0 V waveform on the BUS output. It also receives waveforms and transmits a digital level signal back to a logic IC. The transmitter can drive up to 32 secondary Class B transceivers (see Figures 11 and 12). These secondary nodes may be at ground potentials that are ± 2.0 V relative to the control assembly. Waveshaping will only be maintained during 2 of the 4 corners when the 0 to ± 2.0 V ground potential difference condition exists. The 33990 is a secondary node on the Class B bus. Each secondary transceiver has a 470 ± 10% pF capacitor on its output for EMI suppression purposes, as well as a 10.6 kΩ ± 5% pulldown resistor to ground. The primary node has a 3300 ± 10% pF capacitor on its output for EMI suppression, as well as a 10.6 kΩ 470 pF 1.5 kΩ 3300 pF 24 Secondary Nodes 442 Ω 11280 pF Figure 12. Maximum Number of Nodes 33990 10 Analog Integrated Circuit Device Data Freescale Semiconductor FUNCTIONAL DESCRIPTION FUNCTIONAL PIN DESCRIPTION 31 Secondary Nodes 10.6 kΩ 470 pF 342 Ω 14570 pF Figure 13. Maximum Bus Load Table 6. Class B Bus Capacitance and Resistance Expressions Level Minimum Maximum Capacitance (3.3 x 0.9) + (0.47 x 0.9) = 3.39 nF (3.3 x 1.1) + 25 (0.47 x 1.1) = 16.55 nF Resistance to Ground (1.5 x 0.95) || (10.6 x 0.95) / 25 = 314 Ω (1.5 x 1.05) || (10.6 x 1.05) = 1.38 kΩ 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 11 TYPICAL APPLICATIONS FUNCTIONAL PIN DESCRIPTION TYPICAL APPLICATIONS CLASS B MODULE INPUTS Transmitter Data from the MCU (TX) The Tx input is a push-pull (N-channel / P-channel FETs) buffer with hysteresis for noise immunity purposes. This pin is a 5.0 V CMOS logic level input from the MCU following a true logic protocol. A logic [0] input drives the BUS output to 0 V (via the external pull-down resistor to ground on each node), while a logic [1] input produces a high voltage at the BUS output. A logic [0] input level is guaranteed when the Tx input pin is an open-circuit by virtue of an internal 40 kΩ pull-down resistor. No external resistor is required for its operation. Waveshaping and 4X / Loop This input is a tristateable input: 0 V = normal waveshaping, 5.0 V = waveshaping is disabled for 4X transmitting, and high impedance = loopback mode of operation. This is a logic level input used to select whether waveshaping for the Class B output is enabled or disabled. A logic [0] enables waveshaping, while a logic [1] disables waveshaping. In the 4X mode, the BUS output rise time is less than 2.0 µs and the fall time is less than 5.0 µs (owing to the external RC pull-down to ground). In the loopback condition, the Tx signal is fed back to the Rx output after waveshaping without being transmitted onto the BUS. This mode of operation is useful for system diagnostic purposes. CLASS B MODULE OUTPUTS Transceiver Output (BUS) This is the output driver stage that sources current to the bus. Its output follows the waveshaped waveform input. Its output voltage is limited to 6.25 V to 8.0 V under normal battery level conditions. The limited level is controlled by an internal regulator/clamp circuit. Once the battery voltage drops below 9.0 V, the regulator / clamp circuit saturates, causing the bus voltage to track the battery voltage. A 1.5 kΩ ± 5% external resistor (as well as any 10.6 kΩ pull-down resistors of any secondary nodes) sinks the current to discharge the capacitors during high-to-low transitions. This sourcing output is short circuit-protected (60 mA to 170 mA) against a short to -2.0 V and sinks less than 1.0 mA when shorted to VBAT. If a short occurs, the overtemperature shutdown circuit protects the source driver of the device. In the event battery power is lost to the assembly, the bus transmitter's output stage will be disabled and the leakage current from the BUS output will not source or sink more than 100 mA of current. The transceiver will operate with a remote ground offset of ± 2.0 V, but the lower corners of transmission will not be rounded during this condition. Receiver Output to the Microcontroller (RX) This is a 5.0 V CMOS compatible push-pull output used to send received data to the microcontroller. It does not require an external pull-up resistor to be used. The receiver is always enabled and draws less than 65 µA of current from VBAT. The receive threshold is dependent on the state of the SLEEP pin. The initial state of this output is always a logic [0] after supply voltage is applied, but before the SLEEP pin goes to a logic [1] state. The receiver circuitry is able to operate with VBAT voltages as low as 4.25 V and still remains capable of “waking up” the 33990 when remote Class B activity is detected. When the SLEEP pin is low and message activity occurs on the bus, the receiver passes the bus message through to the microcontroller. The 33990 does not automatically “wake up” from a sleep state when bus activity occurs: the microcontroller must tell it to do so. In the Static Electrical Characteristics table, the maximum voltage for Rx is specified as 4.75 V over an operating range of -40°C to 125°C temperature and 7.0 V to 16 V VBAT. This maximum Rx voltage is compatible with the minimum VDD voltage of microcontrollers to prevent the 33990 from sourcing current to the microcontroller's output. Switched Ground Output (LOAD) Normally this output is a saturated switch to ground, which pulls down the external resistor between the BUS and LOAD outputs. In the event ground is lost to the assembly, the LOAD output will bias itself “off” and will not leak more than 100 µA of current out of this pin. Overtemperature Shutdown If the BUS output becomes shorted to ground for any duration, an overtemperature shutdown circuit “latches off” the output source transistor whenever the die temperature exceeds 150°C to 190°C. The output transistor remains latched off until the Tx input is toggled from a logic [0] to a logic [1]. The rising edge provides the clearing function, provided the locally sensed temperature is 10°C to 15°C below the latch-off temperature trip temperature. Waveshaping Waveshaping is incorporated into the 33990 to minimize radiated EMI emissions. Receiver Protocol The Class B communication scheme uses a variable pulse width (VPW) protocol. The microcontroller provides the VPW decoding function. Once the receiver detects a transition on Rx, it starts an internal counter. The initial “start of frame” bit is a logic [1] and lasts 200 µs. For subsequent bits, if there is a bus 33990 12 Analog Integrated Circuit Device Data Freescale Semiconductor TYPICAL APPLICATIONS FUNCTIONAL PIN DESCRIPTION transition before 96 µs, one logic state is inferred. If there is a bus transition after 96 µs, the other logic state is inferred. The “end of data” bit is a logic [0] and lasts 200 µs. If there is no activity on the bus for 280 µs to 320 µs following a broadcast message, multiple unit nodes may arbitrate for control of the next message. During an arbitration, after the “start of frame” bit has been transmitted, the secondary node transmitting the most consecutive logic [0] bits will be granted sole transmission access to the bus for that message. Loss of Assembly Ground Connection The definition of a loss of assembly ground condition at the device level is that all pins of the 33990, with the exception of BUS and LOAD, see a very low impedance to VBAT. The LOAD pin of the device has an internal transistor switch connected to it that is normally saturated to ground. This pulls the LOAD-side of the external resistor (tied from BUS to LOAD) to ground under normal conditions. The LOAD pin switch is essentially that of an “upside down” FET, which is normally biased “on” so long as module ground is present and biased “off” when loss-of-ground occurs. When a loss of assembly ground occurs, the load transistor switch is selfbiased “off”, allowing no more than 100 µA of leakage current to flow in the LOAD pin. During such a loss of assembly ground condition, the BUS and LOAD pins exhibit a high impedance to VBAT; all other pins will exhibit a low impedance to VBAT. During this condition the BUS pin is prevented from sourcing any current or loading the bus, which would cause a corruption of any data being transmitted on the bus. While a particular assembly is experiencing a loss of ground, all other assembly nodes are permitted to function normally. It should be noted that with other nodes existing on the bus, the bus will always have some minimum / maximum impedance to ground as shown in Table 6, page 11. Loss of Assembly Battery Connection The definition of a loss of assembly battery condition at the device level is that the VBAT pin of the 33990 sees an infinite impedance to VBAT, but there is some undefined impedance between these pins and ground. VBAT +VBAT 33990 47µH BUS 470pF SLEEP 10.6kΩ Primary Node TX MCU RX LOAD Secondary Nodes GND 4X/LOOP Figure 14. Typical Application 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 13 PACKAGING PACKAGE DIMENSIONS PACKAGING PACKAGE DIMENSIONS For the most current package revision, visit www.freescale.com and perform a keyword search using the “98A” listed below. D SUFFIX EF SUFFIX (PB-FREE) 8-PIN PLASTIC PACKAGE 98ASB42564B 33990 14 Analog Integrated Circuit Device Data Freescale Semiconductor REVISION HISTORY REVISION HISTORY REVISION 2.0 3.0 DATE 10/2006 11/2006 DESCRIPTION OF CHANGES • • • Implemented Revision History page Converted to Freescale format Removed Peak Package Reflow Temperature During Reflow (solder reflow) parameter from Maximum Ratings on page 4. Added note with instructions to obtain this information from www.freescale.com. 33990 Analog Integrated Circuit Device Data Freescale Semiconductor 15 How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. 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Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc., 2006. All rights reserved. MC33990 Rev 3.0 11/2006