APPLICATION NOTE Atmel TPM Power Supply Decoupling Guide AT97SC3205 1 Overview The following guidelines are consistent with industry-standard decoupling recommendations for all active system ® components. Effective decoupling of the power supply inputs to the Atmel Trusted Platform Module (TPM) is critical to assuring reliable component performance in a high-density printed circuit board environment. The TPM is a complex system-on-a-chip integrated circuit design containing an internal microprocessor, EEPROM, ROM, and SRAM memories, digital logic, and analog components. The TPM executes firmware operations independently of the external system, as well as executing command operations received over the communications bus. As a result, the TPM is subjected to a wide range of frequencies. These signals must be decoupled from the TPM power supply pins to assure consistently reliable operation over the lifetime of the system. Table 1-1. TPM Power Supply and Ground Pins Industry-Standard Pin 28-lead TSSOP 32-pad VQFN VCC Power Supply 3, 10, 19, 24 1, 8, 22 GND Ground 4, 11, 18, 25 2, 9, 23, 32 2 Atmel TPM Decoupling Recommendations 2.1 Decouple the VCC Pins Effective decoupling of the VCC inputs to the Atmel TPM is critical to assure consistently reliable operation over the lifetime of the system. The Atmel recommendation for a decoupling bypass capacitor (within the range of 2,200pF to 4,700pF) is to be placed as close as possible, less than 5mm, to each of the VCC pins located between each VCC pin and the immediately adjacent GND pin. A 0.1μF decoupling bypass capacitor should be placed at the node where the VCC traces join, which should be as close as possible, less than 10mm, to the TPM. In all cases, this bypass capacitor should be closer than the next closest component. All capacitors should be of high quality with dielectric ratings of X5R or X7R. A low-power state is automatically entered when the device is idle. No further action is required by the system to enter low-power mode. No other component should be placed closer to the TPM VCC pin than the low frequency decoupling capacitor. Each component should be properly decoupled from the power supply signal to prevent injection of noise onto the power plane. All capacitors should have a high quality dielectric rating of X5R or X7R, depending on the system temperature requirements. Atmel-8913B-TPM-AT97SC3205-Decoupling-Guide-ApplicationNote_072014 2.2 Decoupling Diagrams The below figures illustrate power and ground pins only. 27 VCC 3 26 GND 4 25 GND 5 24 VCC 6 23 7 22 8 21 9 20 VCC 10 19 VCC GND 11 18 GND 12 17 13 16 14 15 2200pF 0.1µF 2 2200pF 28 32-pad VQFN 32 31 30 29 28 27 26 25 1 24 2 23 3 22 4 21 5 20 6 19 7 18 8 17 VCC 9 GND VCC 0.1µF VCC GND 2200pF Figure 2-2. 2200pF 28-lead TSSOP 1 2200pF 2200pF Figure 2-1. 10 11 12 13 14 15 16 2200pF GND 3 2 Revision History Doc Rev. Date Comments 8913B 07/2014 Correct VCC TSSOP pins in table, “TPM Power Supply and Ground Pins”. 8913A 06/2014 Initial document release. AT97SC3205 TPM Power Supply Decoupling Guide [APPLICATION NOTE] Atmel-8913B-TPM-AT97SC3205-Decoupling-Guide-ApplicationNote_072014 Atmel Corporation 1600 Technology Drive, San Jose, CA 95110 USA T: (+1)(408) 441.0311 F: (+1)(408) 436.4200 │ www.atmel.com © 2014 Atmel Corporation. / Rev.:Atmel-8913B-TPM-AT97SC3205-Decoupling-Guide-ApplicationNote_072014. 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