LTC4300-1CMS8

LTC4300-1/LTC4300-2 Hot Swappable 2-Wire Bus Buffers FEATURES s s DESCRIPTIO s s s s s s s s s Bidirectional Buffer for SDA and SCL Lines Increases Fanout Prevents SDA and SCL Corruption During Live Board Insertion and Removal from Backplane Isolates Input SDA and SCL Lines from Output Compatible with I2CTM, I2C Fast Mode and SMBus Standards (Up to 400kHz Operation) Small MSOP 8-Pin Package Low ICC Chip Disable: 300ns 10 RECOMMENDED PULL-UP 5 0 0 100 200 CBUS (pF) 300 400 4300-1/2 F04 W U U Figure 4. Bus Requirements for 5V Systems CompactPCI is a trademark of the PCI Industrial Computer Manufacturers Group. sn430012 430012fs LTC4300-1/LTC4300-2 APPLICATIO S I FOR ATIO ciated with hot swapping have settled. Owing to their small capacitance, the SDAIN and SCLIN pins cause minimal disturbance on the backplane busses when they make contact with the connector. Figure 6 shows the LTC4300-2 in a CompactPCI configuration. The LTC4300-2 receives its VCC voltage from one of the long “early power” pins. Because this power is not switched, add a 5Ω to 10Ω resistor between the VCC pins of the connector and the LTC4300-2, as shown in the figure. In addition, make sure that the VCC bypassing on the backplane is large compared to the 0.01µF bypass capacitor on the card. Establishing early power VCC ensures that the 1V precharge voltage is present at the SDAIN and SCLIN pins before they make contact. Connect VCC2 to the output of one of the CompactPCI power supply hot swap circuits. VCC2 is monitored by a filtered UVLO circuit. With the VCC2 voltage powering up after all other pins have established connection, the UVLO circuit ensures that the backplane and card data and clock busses are not connected until the transients associated with hot swapping have settled. Figure 7 shows the LTC4300-1 in a PCI application, where all of the pins have the same length. In this case, connect an RC series circuit on the I/O card between VCC and ENABLE. An RC product of 10ms provides a filter to prevent the LTC4300-1 from becoming activated until the transients associated with hot swapping have settled. Figure 8 shows the LTC4300-2 in an application where the user has a custom connector with pins of three different lengths available. Making VCC2 the shortest pin ensures that all other pins are firmly connected before VCC2 receives any voltage. A filtered UVLO circuit on VCC2 ensures that the VCC2 pin is firmly connected before the LTC4300-2 connects the backplane to the card. Repeater/Bus Extender Application Users who wish to connect two 2-wire systems separated by a distance can do so by connecting two LTC4300-1s back-to-back, as shown in Figure 9. The I2C specification allows for 400pF maximum bus capacitance, severely limiting the length of the bus. The SMBus specification U places no restriction on bus capacitance, but the limited impedances of devices connected to the bus require systems to remain small if rise- and fall-time specifications are to be met. The strong pull-up and pull-down impedances of the LTC4300-1 are capable of meeting riseand fall-time specifications for one nanofarad of capacitance, thus allowing much more interconnect distance. In this situation, the differential ground voltage between the two systems may limit the allowed distance, because a valid logic low voltage with respect to the ground at one end of the system may violate the allowed VOL specification with respect to the ground at the other end. In addition, the connection circuitry offset voltages of the back-to-back LTC4300-1s add together, directly contributing to the same problem. Systems with Disparate Supply Voltages (LTC4300-1) In large 2-wire systems, the VCC voltages seen by devices at various points in the system can differ by a few hundred millivolts or more. This situation is well modelled by a series resistor in the VCC line, as shown in Figure 10. For proper operation of the LTC4300-1, make sure that VCC(BUS) ≥ VCC(LTC4300) – 0.5V. 5V to 3.3V Level Translator and Power Supply Redundancy (LTC4300-2) Systems requiring different supply voltages for the backplane side and the card side can use the LTC4300-2, as shown in Figure 11. The pull-up resistors on the card side connect from SDAOUT to SCLOUT to VCC2, and those on the backplane side connect from SDAIN and SCLIN to VCC. The LTC4300-2 functions for voltages ranging from 2.7V to 5.5V on both VCC and VCC2. There is no constraint on the voltage magnitudes of VCC and VCC2 with respect to each other. This application also provides power supply redundancy. If either the VCC or VCC2 voltage falls below its UVLO threshold, the LTC4300-2 disconnects the backplane from the card, so that the side that is still powered can continue to function. sn430012 430012fs W U U 11 LTC4300-1/LTC4300-2 APPLICATIO S I FOR ATIO U POWER SUPPLY HOT SWAP I/O PERIPHERAL CARD 1 C1 0.01µF ENABLE SDAIN SCLIN VCC LTC4300-1 U1 GND SDAOUT SCLOUT READY R4 10k R5 10k R6 10k CARD_SDA CARD_SCL POWER SUPPLY HOT SWAP I/O PERIPHERAL CARD 2 C3 0.01µF ENABLE SDAIN SCLIN VCC LTC4300-1 U2 GND SDAOUT SCLOUT READY R8 10k R9 10k R10 10k CARD2_SDA CARD2_SCL POWER SUPPLY HOT SWAP I/O PERIPHERAL CARD N C5 0.01µF ENABLE SDAIN SCLIN VCC LTC4300-1 U3 GND SDAOUT SCLOUT READY R12 10k R13 10k R14 10k CARDN_SDA CARDN_SCL BACKPLANE VCC R1 10k BD_SEL SDA SCL R2 10k BACKPLANE CONNECTOR STAGGERED CONNECTOR STAGGERED CONNECTOR STAGGERED CONNECTOR NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURES 3 AND 4 Figure 5. Hot Swapping Multiple I/O Cards into a Backplane Using the LTC4300-1 in a CompactPCI System 12 W U U ••• 4300-1/2 F05 sn430012 430012fs LTC4300-1/LTC4300-2 APPLICATIO S I FOR ATIO BACKPLANE VCC2 BD_SEL VCC SDA SCL R1 10k R2 10k BACKPLANE CONNECTOR STAGGERED CONNECTOR STAGGERED CONNECTOR STAGGERED CONNECTOR NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURES 3 AND 4 Figure 6. Hot Swapping Multiple I/O Cards into a Backplane Using the LTC4300-2 in a CompactPCI System U POWER SUPPLY HOT SWAP 5.1Ω VCC SDAIN SCLIN C2 0.01µF I/O PERIPHERAL CARD 1 C1 0.01µF VCC2 LTC4300-2 U1 GND SDAOUT SCLOUT ACC R4 10k R5 10k R6 10k CARD_SDA CARD_SCL POWER SUPPLY HOT SWAP 5.1Ω VCC SDAIN SCLIN C4 0.01µF I/O PERIPHERAL CARD 2 C3 0.01µF VCC2 LTC4300-2 U2 GND SDAOUT SCLOUT ACC R8 10k R9 10k R10 10k CARD2_SDA CARD2_SCL POWER SUPPLY HOT SWAP 5.1Ω VCC SDAIN SCLIN C6 0.01µF I/O PERIPHERAL CARD N C5 0.01µF VCC2 LTC4300-2 U3 GND SDAOUT SCLOUT ACC R12 10k R13 10k R14 10k CARDN_SDA CARDN_SCL ••• 4300-1/2 F06 W U U sn430012 430012fs 13 LTC4300-1/LTC4300-2 APPLICATIO S I FOR ATIO BACKPLANE VCC R1 10k R2 10k BACKPLANE CONNECTOR SDA SCL C2 0.1µF NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURES 3 AND 4 Figure 7. Hot Swapping Multiple I/O Cards into a Backplane Using the LTC4300-1 in a PCI System BACKPLANE CONNECTOR BACKPLANE VCC2 R1 10k VCC SDA SCL R2 10k STAGGERED CONNECTOR STAGGERED CONNECTOR NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURES 3 AND 4 Figure 8. Hot Swapping Multiple I/O Cards into a Backplane Using the LTC4300-2 with a Custom Connector sn430012 430012fs 14 U I/O PERIPHERAL CARD 1 R3 100k ENABLE SDAIN SCLIN VCC LTC4300-1 U1 GND C1 0.01µF SDAOUT SCLOUT READY R4 10k R5 10k R6 10k CARD_SDA CARD_SCL I/O PERIPHERAL CARD 2 R7 100k ENABLE SDAIN SCLIN C4 0.1µF VCC LTC4300-1 U2 GND C3 0.01µF SDAOUT SCLOUT READY R8 10k R9 10k R10 10k CARD2_SDA CARD2_SCL 4300-1/2 F07 W U U I/O PERIPHERAL CARD 1 C1 0.01µF VCC SDAIN SCLIN C2 0.01µF VCC2 LTC4300-2 U1 GND SDAOUT SCLOUT ACC R4 10k R5 10k R6 10k CARD_SDA CARD_SCL I/O PERIPHERAL CARD 2 C3 0.01µF VCC SDAIN SCLIN C4 0.01µF VCC2 LTC4300-2 U2 GND SDAOUT SCLOUT ACC R8 10k R9 10k R10 10k CARD2_SDA CARD2_SCL 4300-1/2 F08 LTC4300-1/LTC4300-2 APPLICATIO S I FOR ATIO 2-WIRE SYSTEM 1 VCC = 5V C1 0.01µF R1 10k R4 10k LTC4300-1 VCC ENABLE SDA1 SCL1 TO OTHER SYSTEM 1 DEVICES SDAIN SCLIN GND SDAOUT SCLOUT READY LONG DISTANCE BUS SDAOUT SCLOUT READY GND R5 10k R2 R3 5.1k 5.1k R6 10k LTC4300-1 VCC NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURE 4 Figure 9. Repeater/Bus Extender Application PACKAGE DESCRIPTION MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 0.42 ± 0.04 (.0165 ± .0015) TYP RECOMMENDED SOLDER PAD LAYOUT DETAIL “A” 0° – 6° TYP 4.88 ± 0.1 (.192 ± .004) 3.00 ± 0.102 (.118 ± .004) NOTE 4 0.254 (.010) GAUGE PLANE DETAIL “A” 0.18 (.077) SEATING PLANE NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX sn430012 430012fs Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U 2-WIRE SYSTEM 2 VCC C2 0.01µF R7 10k ENABLE SDAIN SCLIN SDA1 SCL1 TO OTHER SYSTEM 2 DEVICES 4300-1/2 F07 U W U U R8 10k 3.2 – 3.45 (.126 – .136) 0.65 (.0256) BSC 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 8 7 65 0.52 (.206) REF 0.53 ± 0.015 (.021 ± .006) 1 1.10 (.043) MAX 23 4 0.86 (.034) REF 0.22 – 0.38 (.009 – .015) 0.65 (.0256) BCS 0.13 ± 0.05 (.005 ± .002) MSOP (MS8) 1001 15 LTC4300-1/LTC4300-2 TYPICAL APPLICATIO S RDROP VCC R1 10k R2 10k C2 0.01µF ENABLE SDA SCL SDAIN SCLIN VCC LTC4300-1 U1 GND SDAOUT SCLOUT READY VCC_LOW R3 10k R4 10k R5 10k SDA2 SCL2 NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURES 3 AND 4 VCC 5V R1 10k SCL SCL R4 10k NOTE: APPLICATION ASSUMES BUS CAPACITANCES WITHIN “PROPER OPERATION” REGION OF FIGURES 3 AND 4 RELATED PARTS PART NUMBER LTC1380/LTC1393 LTC1427-50 LTC1623 LTC1663 LTC1694/LTC1694-1 LT1786F LTC1695 LTC1840 DESCRIPTION Single-Ended 8-Channel/Differential 4-Channel Analog Mux with SMBus Interface Micropower, 10-Bit Current Output DAC with SMBus Interface Dual High Side Switch Controller with SMBus Interface SMBus Interface 10-Bit Rail-to-Rail Micropower DAC SMBus Accelerator SMBus Controlled CCFL Switching Regulator SMBus/I2C Fan Speed Controller in ThinSOTTM Dual I2C Fan Speed Controller COMMENTS Low RON: 35Ω Single-Ended/70Ω Differential, Expandable to 32 Single or 16 Differential Channels Precision 50µA ± 2.5% Tolerance Over Temperature, 4 Selectable SMBus Addresses, DAC Powers up at Zero or Midscale 8 Selectable Addresses/16-Channel Capability DNL < 0.75LSB Max, 5-Lead SOT-23 Package Improved SMBus/I2C Rise-Time, Ensures Data Integrity with Multiple SMBus/I2C Devices 1.25A, 200kHz, Floating or Grounded Lamp Configurations 0.75Ω PMOS 180mA Regulator, 6-Bit DAC Two 100µA 8-Bit DACs, Two Tach Inputs, Four GPI0 sn430012 430012fs ThinSOT is a trademark of Linear Technology Corporation. 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 q FAX: (408) 434-0507 q U 4300-1/2 F08 Figure 10. System with Disparate VCC Voltages C2 0.01µF SDAIN SCLIN VCC VCC2 C1 0.01µF SDAOUT SCLOUT ACC CARD_VCC, 3V R3 10k R2 10k CARD_SDA CARD_SCL LTC4300-2 U1 GND 4300-1/2 F09 Figure 11. 5V to 3.3V Level Translator LT/TP 0602 2K • PRINTED IN USA www.linear.com © LINEAR TECHNOLOGY CORPORATION 2001