DEMO MANUAL DC1941D LTC6820 isoSPI 2-Wire Serial Interface Description Demonstration circuit 1941 is an isoSPI™ transceiver board, based on Linear Technology’s LTC®6820. The LTC6820 provides a method of interconnecting standard serial peripheral interface (SPI) devices using a single twisted pair connection. This proprietary 2-wire interface is called isoSPI. The LTC6820 encodes SPI signals, up to 1Mbps, into a differential isoSPI signal which is transmitted via a simple pulse transformer through a twisted pair. At the other end of the twisted pair, the isoSPI signal can be translated back to SPI (using another LTC6820). MASTER SDO SDI SCK CS Another option would be for the isoSPI to connect to a Linear Technology device with a built-in isoSPI interface, such as the LTC6804. Typically, the LTC6820 will be used in one of two ways: See Figures 1 and 2. Design files for this circuit board are available at http://www.linear.com/demo/DC1941D L, LT, LTC, LTM, Linear Technology and the Linear logo are registered and isoSPI and QuikEval are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. LTC6804 isoSPI PORT LTC6820 (MASTER) MSTR MOSI IP MISO SCK IM CS IPA 120Ω 120Ω IMA Figure 1. A Single LTC6820 Used to Translate an isoSPI Signal into SPI* MASTER µC SDO SDI SCK CS REMOTE SLAVE IC LTC6820 MSTR MOSI IP MISO SCK IM CS 120Ω LTC6820 MSTR SDI SDO SCK CS IP MOSI MISO IM SCK CS 120Ω Figure 2. Two LTC6820 Devices Used to Translate SPI into isoSPI for Long Distance, Isolated Communications * The isoSPI interface is built into numerous Linear Technology products. dc1941dfb 1 DEMO MANUAL DC1941D Overview The DC1941 enables isoSPI connection using the LTC6820. As a reference circuit, its combination of galvanic isolation, common mode filtering, and jumper options enables prototyping of typical applications that employ the LTC6820. This board provides the foundation for translation between SPI and isoSPI signals. The SPI Bus is a synchronous serial data link that uses four single-ended signals to transmit information over short distances (typically on a single PCB). SPI devices communicate in master/slave mode, where the master device initiates the data frame and multiple slave devices are allowed. Because the LTC6820 includes a Master and a Slave mode, LTC6820-based conversion between SPI and isoSPI can occur at the beginning, or upstream in an isoSPI connection. Figure 1 shows a typical example with a LTC6820 connected in Master mode. In this example, a DC1941 connects the SPI port of a microcontroller to an isoSPI-based slave device (such as Linear Technology's LTC6804). In Figure 2, two DC1941s can be used to translate an endto-end bidirectional SPI interface into an isoSPI interface. One DC1941 uses Master mode; the other, Slave mode. This configuration allows the outermost SPI devices to be galvanically isolated, and enables long distance, noise immune communication. The 2-wire isoSPI interface is accessible using standard RJ45 connectors (J1 on the DC1941). Standard RJ45 connectors allow the use of simple CAT5 cable1 to interconnect isoSPI ports. Other Linear Technology demo boards with isoSPI also use RJ45 connectors for simple interconnection. The LTC6820’s four SPI signals are accessible via J2 (14-pin ribbon connector) or JP1 (6-pin header connector). The SPI signal can be also translated to a USB signal for a connection to a PC using Linear Technology's DC2026 (Linduino Interface). The Linduino is connected to the DC1941 through J2. Power to the DC1941 can be supplied via the SPI connection (J2, JP1) or the turrets on the board. Typically, the most convenient method to provide power is to connect J2, through a 14 pin ribbon cable, to a DC2026 Linduino board. The Linduino DC2026 sends power on pin 2 of this connector; it can be 2.5, 3.3, or 5V depending on a jumper on the DC2026. Whichever voltage is chosen on the DC2026 will be available at pin 2 of J2, assuming ribbon cable connection. That said, the DC1941 board, with its LTC6820, does not require connection to a DC2026. Power can be provided directly to the DC1941 at turrets from an external source. In addition, because the VCC and VCCS pins of the LTC6820 do not need to be coupled, one can bring in two distinct supplies to the DC1941 board. Such a configuration might be needed if the I/O voltage of the SPI signals differs from the nominal supply voltage of the LTC6820. 1 A single twisted pair inside the CAT5 is used for the isoSPI interconnection. Jumpers Jumper settings are provided on the DC1941 to configure the SPI mode, speed and master/slave operation. Jumpers are also provided to configure the isoSPI shutdown and output power level, as well as power supply options. 2 dc1941dfb DEMO MANUAL DC1941D Jumpers JP2 – VCC to EXT/DC590: JP7,8 – PHA/POL: EXT: Set to EXT if the DC1941 is powered from an external supply. In such a case, power is provided typically at the turrets on the board. POL indicates whether SCK idles high (1) or low (0). PHA indicates latching on the first edge (0) or the second edge (1). DC590B (DEFAULT): Set to DC590 if the DC1941 is powered through the 14-pin ribbon cable connector (J2 on the DC1941). The DC2026 connects to the DC1941 through this 14-pin ribbon cable. These jumpers set the SPI mode per the following table. JP3 – EN/SLP_EN: EN: Set to have the LTC6820 always enabled. SLP_EN (DEFAULT): When selected, the LTC6820 will enter shutdown after 4ms of inactivity and will require a wake up pulse. JP4 – SLOW/FAST: SLOW: Set for SPI clock frequencies of 100kHz or less. FAST (DEFAULT): Set for SPI clock frequencies greater than 100kHz. JP5 – MASTER/SLAVE: The LTC6820 can sit at the start of an SPI connection when in Master mode. It can alternatively sit at the end of an isoSPI connection and talk to a slave SPI device when it is in Slave mode. MASTER(DEFAULT): Configures the SPI for master mode; the LTC6820 will operate as the isoSPI master. When this jumper is set to ‘master’, the J2 connector should be connected to a SPI master. SLAVE: Configures the SPI for slave mode; the LTC6820 will operate as an isoSPI slave. The DC1941 should be connected to a SPI slave device. JP6 – VCCS to VCC/EXT: Table 1 MODE POL PHA 0 0 0 1 0 1 2 1 0 3 (Default) 1 1 Set to mode 3 for use with LTC6804. If POL = 0, SCK idles low. Data is latched on the rising (first) clock edge if PHA = 0 and on the falling (second) clock edge if PHA = 1. If POL =1, SCK idles high. Data is latched on the falling (first) clock edge if PHA = 0 and on the rising (second) clock edge if PHA = 1. The two most common configurations are mode 0 (PHA = 0 and POL = 0) and mode 3 (PHA = 1 and POL = 1) because these modes latch data on a rising clock edge. For example, in the Default case of mode 3, SCK normally idles high; the first latching edge is the first rise after the reset to 0 out of idle. JP9,10 – VTH1/VTH2: VTH1: Sets the LTC6820 output drive to 1V, and the receiver input threshold to 500mV. VTH2 (DEFAULT): Sets the LTC6820 output drive to 1V, and the receiver input threshold to 600mV. The VTH2 settings are compatible with other Linear Technology isoSPI-based demo boards. VCC (DEFAULT): Sets the LTC6820 SPI input/output supply voltage (VCCS) to VCC, which sets the SPI logic levels to VCC. EXT: Allows the SPI input/output supply (VCCS) to be connected to a separate voltage from VCC, which allows the logic levels to be set to a different voltage. An external supply can be connected on the turret labeled VCCS. dc1941dfb 3 DEMO MANUAL DC1941D Setup: DC1941 to isoSPI-Based Demo Board A single Master mode DC1941 converts SPI to isoSPI. 1.Connect a USB port to DC2026. 2.Connect DC2026 14-pin connector to DC1941 14-pin connector (J2) with 14-wire ribbon. 3.The DC1941 must be in Master mode (JP5 = Master). It can take power from the DC2026 (JP2 = DC590). 4.Connect J1 of DC1941 to isoSPI-based demo board Port A using an Ethernet Patch Cable. 5.Check jumpers on all boards and adjust if necessary. 6.Refer to the Linduino demo manual for software instructions. Figure 3. Hardware and Jumper Settings to an isoSPI-based Demo Board (Illustrated with the DC1894, LTC6804-1 Demo Board) 4 dc1941dfb DEMO MANUAL DC1941D LTC6820 to LTC6804 Setup Figure 4. Hardware and Jumper Settings to an isoSPI-based Demo Board (Illustrated with the DC1942, LTC6804-2 Demo Board) Figure 5. (Illustrated with Multiple DC1942, LTC6804-2 Demo Boards) Multidrop Example dc1941dfb 5 DEMO MANUAL DC1941D Setup: DC1941 to DC1941 for SPI to SPI with Isolation The combination of one Master mode DC1941 and one Slave mode DC1941 enables SPI with isolation using isoSPI. 1.Connect a USB port to DC2026. 2.Connect DC2026 14-pin connector to DC1941 14-pin connector (J2) with 14-wire ribbon. 3.The DC1941 must be in Master mode (JP5 = Master). It can take power from the DC2026 (JP2 = DC590). 4.Connect J1 of DC1941 to J1 of a second DC1941 using an Ethernet Patch Cable. 5.This second DC1941 must be in Slave mode (JP5 = Slave). It can take power from an external supply (JP2 = EXT). 7.Check jumpers on all boards and adjust if necessary. 8.Refer to the Linduino Demo Manual for software instructions. If the SPI-based slave board is a Linear Technology demo board, then it may have the same 14-pin connector. In this case, this demo board can connect to J2 of the second DC1941 board. Often engineers will use QuikEval™ software from Linear Technology when evaluating an SPI-based demo board. This paradigm remains unchanged when there is an isoSPI bridge between the DC2026 SPI port and the SPI-based demo board. QuikEval will operate normally; a host PC that interfaces with the DC2026 will not know anything about the isoSPI intermediary physical layer. 6.Connect the SPI of the second DC1941 board to a SPI slave device. Figure 6. Hardware and Jumper Settings to Connect Two DC1941s and Add isoSPI Capability to a Standard SPI Slave 6 dc1941dfb 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. A B C D AUX EEGND EEVCC EESCL EESDA CS SCK/SCL MISO MOSI/SDA 5V V+ J2 MOLEX, 87831-1420 GND 13 GND 8 GND 3 14 12 10 11 9 6 4 5 7 2 1 5 4 3 2 1 A2 24LC025-I/ST SDA WP SCL A1 VSS VCC 5 6 7 8 R19 4.99K VCC E1 VCC 2.7V - 5.5V A0 U2 R18 4.99K 3 2 1 E2 VCC DC590 JP2 EXT GND 5 3 1 JP6 3 2 1 1 2 3 1 2 3 JP8 POL 1 0 JP3 8 7 6 5 4 3 2 1 JP7 4 1. ALL CAPACITORS AND RESISTORS ARE 0603. 3 2 1 PHA VCC PHA 1 0 C1 0.1uF VCC IM MSTR CS8 POL SLOW SCK IP GND MISO VCCS IBIAS VCMP MOSI U1 LTC6820 EN SLP_EN EN ENABLE E4 0.1uF C2 VCCS VCCS GND NOTES: UNLESS OTHERWISE SPECIFIED, EXT VCC SPI JP1 VCC R3 R4 2K 2K E3 VCCS 1.5V - 5.5V VCCS 6 4 2 4 1 R1 1K R8 60.1 R9 60.1 E6 4 1 3 2 3 2 JP9 4 1 3 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. 2 10nF C49 R11 294 R10 294 JP4 3 2 1 VCC 1 REV 2 SCALE = NONE DATE: N/A SIZE 1 2 3 2 1 DESCRIPTION R13 0 R12 0 JP5 isoIP isoIM 1 3 5 7 isoSPI J1 RJ45 2 4 6 8 Tuesday, February 09, 2016 LTC6820 DEMO CIRCUIT 1941D 1 SHEET 1 isoSPI TWO WIRE SERIAL INTERFACE IC NO. DATE 1 OF 1 REV. 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only R16 0 APPROVED CUYLER L. 02-09-16 E10 E9 R15 DNS R14 0 SLAVE MASTER 1ST PROTO 1 REVISION HISTORY TECHNOLOGY T5 CEEH96B SUMIDA IM 4 3 IP SLOW E8 E7 0 1 __ ECO CUYLER L. TITLE: SCHEMATIC AK APPROVALS T2 3 2 DLW43SH101XK2 VTH2 VTH1 DLW43SH101XK2 T1 R2 1K R7 1.2K CUSTOMER NOTICE C5 10nF JP10 VTH1 VTH2 R6 806 VICMP 1 LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED APP ENG. CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. 9 10 11 12 13 14 15 16 3 2 E5 IBIAS 3 11 12 5 A B C D DEMO MANUAL DC1941D Schematic Diagram dc1941dfb 7 DEMO MANUAL DC1941D DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation 8 dc1941dfb Linear Technology Corporation LT 0616 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2013