Rev: 111607 DS3205 Hot-Swappable Bus Buffer for I2C, SMBus, IPMI, and ATCA Features General Description The DS3205 bus buffer enables hot insertion and extraction of boards without corruption of the backplane’s 2-wire bus (I2C, SMBus™, IPMI, etc.). When a board is inserted, the DS3205 presents highimpedance SCL and SDA connections to the backplane until VDD rises above 2.5V. During normal operation, the DS3205 provides bidirectional buffering to keep backplane and board capacitances isolated. Rise-time accelerators on each 2-wire bus pin enable the use of lower current pullup resistors while still meeting rise-time requirements. Applications Hot-Swappable Boards for AdvancedTCA®, CompactPCI®, VME, and Other Backplanes in Chassis-Oriented Telecom, Datacom, Computing, and Storage Systems Capacitance Buffer Bus Extender Fault Isolator Ordering Information PART TEMP RANGE DS3205DN+ -40°C to +85°C PINPACKAGE 14 TDFN PKG CODE T1433-1 2 ♦ Compliant to PICMG 3.0 IPMI I C Requirements ♦ Bidirectional Buffer for SCL and SDA Lines ♦ Compatible with I2C, I2C Fast Mode, SMBus, IPMI, and ATCA® Standards (Up to 400kHz) ♦ Prevents Corruption of System SCL and SDA Lines During Live Insertion/Removal of Boards ♦ Increases Fanout by Connecting Board Bus to Backplane Bus with < 10pF Additional Load ♦ Automatically Delays Initial Bus Connection Until Both Bus Segments Are Idle ♦ SCL and SDA Pins High-Z When VDD = 0V ♦ 1V Precharge on SCL and SDA Lines ♦ ENABLE Input Pin Connects or Isolates Buses ♦ READY Output Pin Indicates “Connected” ♦ FAULT Output Pin Indicates “Stuck Bus” ♦ Optional Rise-Time Accelerators on All Bus Pins ♦ Configurable Rise-Time Accelerator Slew Rate Threshold (0.8V/μs or 1.25V/μs) ♦ Supports Clock Stretching and Multiple Bus Master Arbitration and Synchronization ♦ Optionally Disconnects Board from Backplane When Bus is Stuck Low for ≥ 30ms ♦ Optionally Attempts to Recover a Stuck Bus by Clocking Board SCL ♦ ±15kV ESD Protection (Human Body Model) on Bus Pins ♦ Wide Operating Voltage Range: 2.7V to 5.5V ♦ 5V Tolerant I/Os ♦ Tiny 14-Pin, 3mm x 3mm TDFN Package +Denotes a lead-free package. SMBus is a trademark of Intel Corp. ATCA, AdvancedTCA, and CompactPCI are registered trademarks of PCI Industrial Computer Manufacturers Group (PICMG). Maxim Integrated Products 1 Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, go to: www.maxim-ic.com/errata. For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. ____________________________________________________________________________________________ DS3205 Table of Contents 1. TYPICAL ATCA APPLICATION ......................................................................................................5 2. APPLICABLE DIAGRAMS ..............................................................................................................6 3. PIN DESCRIPTIONS ........................................................................................................................9 4. FUNCTIONAL DESCRIPTION .......................................................................................................11 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 5. OVERVIEW ....................................................................................................................................11 STARTUP ......................................................................................................................................11 RISE-TIME ACCELERATORS ...........................................................................................................11 READY OUTPUT PIN.....................................................................................................................11 ENABLE INPUT PIN ......................................................................................................................11 STUCK BUS CONDITION .................................................................................................................11 BUS CAPACITANCE REQUIREMENTS ...............................................................................................12 PULLUP RESISTOR ........................................................................................................................12 OPERATING PARAMETERS ........................................................................................................13 5.1 ELECTRICAL CHARACTERISTICS .....................................................................................................13 6. PIN CONFIGURATION ..................................................................................................................16 7. PACKAGE INFORMATION ...........................................................................................................17 7.1 14-PIN TDFN WITH EXPOSED PAD (21-0137) ................................................................................17 8. THERMAL INFORMATION ............................................................................................................19 9. DATA SHEET REVISION HISTORY..............................................................................................20 Rev: 111607 2 of 20 ____________________________________________________________________________________________ DS3205 List of Figures Figure 1-1. Typical Application (ATCA Blade) ............................................................................................................. 5 Figure 2-1. Block Diagram ........................................................................................................................................... 6 Figure 2-2. Backplane-to-Card Connection Detail....................................................................................................... 7 Figure 2-3. DS3205 State Diagram ............................................................................................................................. 8 Figure 6-1. 14-Pin TDFN with Exposed Pad Pin Configuration................................................................................. 16 Rev: 111607 3 of 20 ____________________________________________________________________________________________ DS3205 List of Tables Table 3-1. Pin Descriptions.......................................................................................................................................... 9 Table 5-1. Power Supply ........................................................................................................................................... 13 Table 5-2. Startup Characteristics ............................................................................................................................. 13 Table 5-3. I2C Bus Pins Characteristics..................................................................................................................... 14 Table 5-4. Device Control Pins Characteristics ......................................................................................................... 14 Table 5-5. Timing Characteristics .............................................................................................................................. 15 Table 8-1. Thermal Properties—14-Pin TDFN Package ........................................................................................... 19 Rev: 111607 4 of 20 ____________________________________________________________________________________________ DS3205 1. Typical ATCA Application Figure 1-1 shows an ATCA blade application for the DS3205. In this application the DS3205 is used as a buffer for the Intelligent Platform Management Bus (IPMB). The IPMB is used in ATCA for communications between and management of all Field Replaceable Units (FRUs). The DS3205 is compliant with the ATCA IPMB requirements as specified in PICMG 3.0 AdvancedTCA Base Requirements. Figure 1-1. Typical Application (ATCA Blade) Backplane Connector Blade connector with multiple pin lengths provides "Staged" contact. Power and ground connect first, then SCL/SDA, then ENABLE last. 3.3V BACKPLANE_SCL 10k BACKPLANE_SDA DS3205 VCC SCLIN SCLOUT SDAIN SDAOUT 10k BOARD_SCL 10k BOARD_SDA READY FAULT ACOE ENABLE GND 0.01µF ASR ACIE SBDIS SBCLK 5V 10k 100k Rev: 111607 5 of 20 ____________________________________________________________________________________________ DS3205 2. Applicable Diagrams Figure 2-1. Block Diagram BACKPLANE-TO-CARD CONNECTION SCLIN SCLOUT ASR ACOE DS3205 ACIE BACKPLANE-TO-CARD CONNECTION SDAIN SDAOUT 1 VOLT PRE-CHARGE 150K 150K 150K 150K READY PRE CONNECT FORCE CLOCKING + + - - + - STOP BIT, BUS IDLE, AND CONNECT STATE MACHINE + - SBDIS FAULT SBCLK ENABLE VSS UNDER VOLTAGE DETECTION VREF Rev: 111607 VDD 6 of 20 ____________________________________________________________________________________________ DS3205 Figure 2-2. Backplane-to-Card Connection Detail SxIN SxOUT fast ena SLEW RATE DETECT acc acc ena fast SLEW RATE DETECT 150k 150k + + - - SxIN ACIR ASR REF REF PRECHARGE Rev: 111607 ACOE SxOUT FORCE CLOCK 7 of 20 ____________________________________________________________________________________________ DS3205 Figure 2-3. DS3205 State Diagram INITIAL 130µs stuck bus = 1 & SBCLK = 1 & SBDIS = 0 precharge on STUCK BUS CLOCKING BUS WAIT (input stop + input idle) & output high Hi Z off READY = 1 FORCE 16 CLOCKS AT SCLOUT PIN stuck bus = 0 + SBCLK = 0 stuck bus = 0 + (SBCLK = 0 & SBDIS = 0) COMPLETED 16 FORCED CLOCKS STUCK BUS DISCONNECT ACTIVE stuck bus = 1 & SBCLK = 0 & SBDIS = 1 input stop = rising edge on SDAIN while SCLIN high input idle = SDAIN and SCLIN high for 140µs stuck bus = SDAOUT or SCLOUT low for 30ms Rev: 111607 8 of 20 ____________________________________________________________________________________________ DS3205 3. Pin Descriptions Table 3-1. Pin Descriptions NAME PIN TYPE FUNCTION Enable Input. This input pin establishes the board-to-backplane connection when driven to a level above VDD/2 (approximately) with 50mV hysteresis. 0 = Disable connection and enter low-power mode. 1 = Enable connection of backplane and board buses. ENABLE 1 I SCLOUT 2 I/O Serial Clock Output. This pin is connected to the board’s SCL signal. SDAOUT 3 I/O Serial Data Output. This pin is connected to the board’s SDA signal. ACIE ACOE 4 5 I Accelerator Current on Inputs Enable. This input pin enables/disables the risetime accelerators on the bus input pins. 0 = Disable rise-time accelerator on SCLIN and SDAIN. 1 = Enable rise-time accelerator on SCLIN and SDAIN. I Accelerator Current on Outputs Enable. This input pin enables/disables the risetime accelerators on the bus output pins. 0 = Disable rise-time accelerator on SCLOUT and SDAOUT. 1 = Enable rise-time accelerator on SCLOUT and SDAOUT. ASR 6 I Accelerator Slew Rate Threshold Select. This input pin selects the rate for the rise-time accelerators. 0 = 0.8V/μs 1 = 1.25V/μs VSS 7 P Ground READY FAULT SBCLK SBDIS Rev: 111607 8 9 10 11 Ood Connected Status Indicator. This is an open-drain output that goes high when the device is in the ACTIVE state. See the state diagram in Figure 2-3. This pin should have an external 10kΩ pullup resistor. 0 = Backplane and board buses not connected. 1 (float) = Backplane and board buses connected. Ood Active-Low Bus Fault Indicator. This open-drain output pin indicates a “stuck bus” condition when = 0. This pin should have an external 10kΩ pullup resistor. 0 = Either SCLOUT or SDAOUT has been low > 30ms. 1 = No stuck bus fault. I Stuck Bus Clocking Enable. Asserting this pin high causes the DS3205 to drive clock pulses onto the SCLOUT pin in an attempt to free a stuck bus when a “stuck bus” condition has been detected. See Section 4 and Figure 2-3 for more information on the stuck bus condition. 0 = Disable automatic clocking during stuck bus fault. 1 = Enable automatic clocking during stuck bus fault. Note: Asserting both SBDIS and SBCLK high at the same time is not valid and can produce unwanted results. I Stuck Bus Disconnect Enable. Asserting this pin high causes the DS3205 to disconnect the backplane signals from the board signals when a “stuck bus” condition has been detected. See Section 4 and Figure 2-3 for more information on the stuck bus condition. 0 = Disable automatic disconnect on stuck bus fault. 1 = Enable automatic disconnect on stuck bus fault. Note: Asserting both SBDIS and SBCLK high at the same time is not valid and can produce unwanted results. 9 of 20 ____________________________________________________________________________________________ DS3205 NAME PIN TYPE SDAIN 12 I/O Serial Data Input. This pin is connected to the backplane SDA signal. SCLIN 13 I/O Serial Clock Input. This pin is connected to the backplane SCL signal. VDD 14 P Power Supply. 2.7V to 5.5V EP — — Exposed Pad I/O I Ood P = = = = Rev: 111607 FUNCTION Input/Output Input Output, Open Drain Power 10 of 20 ____________________________________________________________________________________________ DS3205 4. Functional Description 4.1 Overview See the DS3205 state diagram in Figure 2-3. 4.2 Startup When the DS3205 is first powered on, it is in a low-power state with the SCLIN, SCLOUT, SDAIN, and SDAOUT pins in a high-impedance state. If the ENABLE pin is pulled high, the DS3205 waits until the supply voltage rises above approximately 2V, when the precharge circuitry becomes active and forces 1V through 150kΩ resistors into all SCL and SDA pins. The 1V precharge minimizes bus disturbances when the backplane and card are at opposing logic levels. The DS3205 then waits about 130μs for the external connections and internal circuitry to settle. After this wait time, the DS3205 enters the BUS WAIT state where it looks for either a stop bit on the input (rising edge on the SDAIN pin while SCLIN remains high) or an input bus idle condition (SDAIN and SCLIN both high for 140μs) while both SDAOUT and SCLOUT pins are high. Once these conditions are met, the precharge circuit is turned off and the DS3205 enters the ACTIVE state. While in the ACTIVE state, the DS3205 establishes a bidirectional connection between the SDAIN and SDAOUT pins and the SCLIN and SCLOUT pins. The voltage on any bus pin is buffered and offset an additional +75mV (approximately) to the other side. Whichever side is pulled closest to ground has priority. For example, if SCLOUT is pulled closer to ground than SCIN, SCIN is driven to a voltage 75mV higher than SCOUT. 4.3 Rise-Time Accelerators If current acceleration is enabled through the ACIE or ACOE pins, the DS3205 pulls up more strongly, shortening the rise time compared to using only the external bus pullup resistors. The pullup provided by the driver during acceleration is approximately 3.5mA instead of its usual 100μA. This acceleration current on one side of the buffer is activated when the bus voltage on the other side is greater than 0.6V and its slew rate is greater than 0.8V/μs (ASR low) or 1.2V/μs (ASR high) and the corresponding ACIE and/or ACOE pin is pulled high. The acceleration current is deactivated after the accelerated bus pin rises within 0.9V of VDD. For example, if the ACOE pin is high, when the SCLIN pin rises above 0.6V with a fast slew rate, the SCLOUT pin is pulled up towards VDD with more than 3mA of current. This current ceases when the SCLOUT pin rises to within 0.9V of VDD. 4.4 READY Output Pin The READY pin is pulled low whenever the DS3205 is not in its ACTIVE state. An external pullup resistor brings the READY pin high when the bidirectional connection is established. 4.5 ENABLE Input Pin If the ENABLE pin is pulled low, the backplane side disconnects from the board side and the device enters a lowpower state with the READY pin asserted low. Also, the rise-time accelerators and precharge circuitry are disabled. Setting ENABLE low causes the device to disconnect the board side from the backplane side and enter the lowpower mode. 4.6 Stuck Bus Condition If the SDAOUT and SCLOUT pins remain low for 30ms the bus is assumed to be stuck. This 30ms timeout is restarted only when the SDAOUT and SCLOUT pins are both high. The FAULT pin pulls low and remains low until the bus is unstuck. If the SBCLK pin is high, the DS3205 attempts to unstick the bus by first disconnecting all SDA and SCL pins for 50μs, then pulls down on the SCLOUT pin 16 times at a 8kHz rate. If the bus becomes unstuck during this process (SDAOUT and SCLOUT both go high), the DS3205 returns to the BUS WAIT state. The precharge circuitry becomes active, and, as soon as a stop bit or bus idle is detected on the input while both Rev: 111607 11 of 20 ____________________________________________________________________________________________ DS3205 SDAOUT and SCLOUT pins are high, the DS3205 goes to the ACTIVE state, reestablishing bidirectional buffering. If the bus remains stuck after 16 clocks, the DS3205 sits with all SDA and SCL pins precharged until SDAOUT and SCLOUT go high. If the SBCLK pin is low and the SBDIS pin is high, the DS3205 only precharges the SDA and SCL pins until the bus becomes unstuck. If neither SBCLK nor SBDIS are high, the DS3205 remains in its ACTIVE state, but the FAULT pin pulls low as an alert that the bus is stuck. If the DS3205 is in the STUCK BUS CLOCKING state, setting the SBCLK pin low forces the part into the BUS WAIT state. If the DS3205 is in the STUCK BUS DISCONNECT state, setting the SBDIS pin low forces the part into the BUS WAIT state. These transitions are shown in the state diagram in Figure 2-3. Returning to the BUS WAIT state resets the 30ms stuck bus counter. 4.7 Bus Capacitance Requirements A minimum of 47pF bus capacitance is required on 5V systems; 3.3V systems require a minimum of 22pF for proper operation. Buses with less capacitance should be provisioned with an added capacitor to ground in order to maintain the minimum required capacitance. The DS3205 tolerates capacitance levels slightly marginal with respect to these requirements. 4.8 Pullup Resistor When SCLIN, SCLOUT, SDAIN, or SDAOUT is driven to a logic-low level, that pin's corresponding output pin is driven to a slightly higher level. For example, if SDAOUT is driven low, SDAIN is driven to a level according to the following formula. VSDAIN = VSDAOUT + 75mV + (VDD / R) × 20Ω EXAMPLE: IF R = bus pullup resistor = 10kΩ IF VDD = 3.3V IF VSDAOUT = 10mV VSDAIN = 91.6mV (typical) Rev: 111607 12 of 20 ____________________________________________________________________________________________ DS3205 5. Operating Parameters ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin with Respect to VSS (except VDD)…….………………………………………….0.5V to 6.0V Supply Voltage Range (VDD) with Respect to VSS…….………….……………………………………………0.5V to 6.0V Operating Temperature Range.…………………………………………………………………….-40°C to +85°C (Note 1) Storage Temperature Range………………………………………………………………………………..-55°C to +125°C Soldering Temperature..………………………………………………Refer to the IPC/JEDEC J-STD-020 Specification. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability. Ambient operating temperature range when device is mounted on a four-layer JEDEC test board with no airflow. Note 1: Specifications to -40°C are guaranteed by design and not production tested. 5.1 Electrical Characteristics Table 5-1. Power Supply (VDD = 2.7V to 5.5V, TA = -40°C to +85°C.) PARAMETER SYMBOL CONDITIONS Supply Voltage VDD Supply Current IDD VDD = 5.5V, VSDAIN = VSCLIN = 0V Shutdown Current ISD VENABLE = 0V, all other pins at VDD or VSS MIN TYP MAX UNITS 5.5 V 4 7 mA 200 500 μA MIN TYP MAX UNITS 0.75 1.00 1.25 V VDD / 2 VDD x 0.7 V 2.7 Table 5-2. Startup Characteristics (VDD = 2.7V to 5.5V, TA = -40°C to +85°C.) PARAMETER Precharge Voltage SYMBOL VPRE CONDITIONS SDA, SCL floating (Note 1) ENABLE Threshold Rising VTHR (EN, RISE) Enabling ENABLE Threshold Falling VTHR (EN, FALL) Disabling VDD x 0.3 VDD / 2 V Enable Time tEN ENABLE high ≥ READY 350 420 μs Disable Time tDIS ENABLE low ≥ READY 25 50 ns Bus Idle Time tIDLE 350 430 μs SDAIN to READY After STOP tSTOP 0.7 1.0 μs SCLOUT/SDAOUT to READY tREADY 0.6 1.0 μs Rev: 111607 (Note 2) 13 of 20 ____________________________________________________________________________________________ DS3205 Table 5-3. I2C Bus Pins Characteristics (VDD = 2.7V to 5.5V, TA = -40°C to +85°C) PARAMETER SYMBOL CONDITIONS Input/Output Offset Voltage VOS ENABLE Input Current IEN ENABLE between VSS and VDD CBUS Applies to SCLIN, SDAIN, SCLOUT, SDAOUT pins; signals between -0.5V and 3.65V, VDD between 0V and 5.5V I2C Capacitance (Note 3) IOFF (BUS) ENABLE = VSS or VDD < VDD,UV Output Low Open-Drain Outputs VOL (OD) Applies to READY and FAULT pins, IPULLUP = 3mA I2C Bus VOUTLOW VOL (BUS) IIN = -3mA I C Bus Clock TYP MAX 75 Leakage Current on I2C Pins 2 MIN UNITS mV +1 μA 10 pF +10 μA 0.4 V 0.3 0.5 V 30 45 ms -1 3 -10 See Table 5-5 Bus Stuck Low Timer tSTUCK SDAOUT or SCLOUT = low 15 Transient-Boosted Pullup Current IPULL Low to high transition on SDA, SCL pins; VDD = 0.3V 1 mA Table 5-4. Device Control Pins Characteristics (VDD = 2.7V to 5.5V, TA = -40°C to +85°C) PARAMETER SYMBOL Logic Input Threshold Voltage VTHR (LOG) Logic Input Hysteresis VHYS ENABLE Input Threshold Input Leakage Leakage Current on Open-Drain Outputs Lead Capacitance Rev: 111607 IIL IOFF (OD) CIO CONDITIONS Applies to SBDIS, SBCLK, ASR, ACOE, and ACIE inputs Any logic input pin except ENABLE (Note 3) See Table 5-2 Applies to SBDIS, SBCLK, ASR, ACOE, ACIE, and ENABLE Applies to READY and FAULT pins, ENABLE = VSS READY, ENABLE, SBDIS, SBCLK, ASR, ACOE, ACIE, FAULT pins MIN TYP MAX UNITS 1.6 1.8 2.0 V 50 mV -10 +10 μA -10 +10 μA 10 pF 14 of 20 ____________________________________________________________________________________________ DS3205 Table 5-5. Timing Characteristics (VDD = 2.7V to 5.5V, TA = -40°C to +85°C) PARAMETER SYMBOL CONDITIONS MIN 0 TYP MAX UNITS 400 kHz Operating Frequency fBUS Bus Free Time Between START and STOP Condition fBUF (Note 3) 1.3 μs Hold Time After Repeated START Condition tHD,START (Note 3) 0.6 μs Repeated START Condition Setup Time tSU,START (Note 3) 0.6 μs STOP Condition Setup Time tSU,STOP (Note 3) 0.8 μs Clock Low Period tLOW (Note 3) 1.3 μs Clock High Period tHIGH 0.6 μs Clock-Data Fall Time tF (Note 4) 20 + 0.1CB Clock-Data Rise Time tR (Notes 3, 4) 20 + 0.1CB Note 1: Applies over full operational temperature range. Note 2: Delays that can occur after enable and/or idle time have passed. Note 3: Guaranteed by design. Not production tested. Note 4: CB = Total capacitance of one bus line (pF). Note 5: IPULL varies with temperature and voltage. Rev: 111607 250 ns ns 15 of 20 ____________________________________________________________________________________________ DS3205 6. Pin Configuration Figure 6-1. 14-Pin TDFN with Exposed Pad Pin Configuration Rev: 111607 16 of 20 ____________________________________________________________________________________________ DS3205 7. Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. The package number provided for each package is a link to the latest package outline information. Go to www.maxim-ic.com/packages.) 7.1 14-Pin TDFN with Exposed Pad (21-0137) Rev: 111607 17 of 20 ____________________________________________________________________________________________ DS3205 Rev: 111607 18 of 20 ____________________________________________________________________________________________ DS3205 8. Thermal Information Table 8-1. Thermal Properties—14-Pin TDFN Package PARAMETER VALUE Target Ambient Temperature Range -40°C to +85°C Theta J (Die Junction Temperature Range) -40°C to +125°C Rev: 111607 19 of 20 ____________________________________________________________________________________________ DS3205 9. Data Sheet Revision History REVISION DATE 111607 PAGES CHANGED DESCRIPTION — Initial data sheet release. Rev: 111607 20 of 20 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products.