Freescale Semiconductor Application Note Document Number: 926-77273 Rev. 1.3 02/2009 i.MX31 PDK 1.5 Power Measurements Application Note This document describes the current measurement capabilities of the 3-Stack board and explains how to obtain these measurements from the Debug board. Contents 1 Overview.................................................................2 1.1 Maxim MAX4071 Modules ................................2 1.2 Debug Board Connector for Measurements .......3 2 Measuring the Current .............................................5 Freescale Semiconductor, Inc. _______________________________________________________________________ 1 Overview The 3-Stack board provides the functionality for measuring voltage and current. Checking these measurements enables you to determine the overall product efficiency. 1.1 Maxim MAX4071 Modules The CPU and Personality boards contain seven Maxim MAX4071 modules, which reduce power supply noise and improve the accuracy of the readings. Figure 1 illustrates the MAX4031 module layout. Figure 1 MAX4071 Connection Diagram The power measurement system provides a way to easily test the system, using four output voltages and seven amplified currents. 2 i.MX31 PDK 1.5 Power Measurements Application Note, Rev. 1.3 Freescale Semiconductor Table 1 describes the voltage and current outputs. Table 1 Voltage and Current Outputs Identifier Voltage Voltage Voltage Voltage Current Current Current Current Current Current Current Category NA NA NA NA CPU CPU CPU Personality Personality Personality Personality Description VMAIN 5V from Wall power supply Battery Voltage 1.8V peripheral voltage Atlas SW1: MX31 ARM Core and L2 Atlas SW2: 1.8V combined to MX31, mDDR and NAND VMAIN: Combined Battery and/or Wall Supply 1.8V combined to peripherals Lithium Prismatic Battery 5V Wall Power Supply (power jack on Personality board) 3.3V to Hard Drive 1.2 Debug Board Connector for Measurements Figure 2 identifies the connector on the Debug board that is used to obtain measurements. Figure 3 provides an enlarged view of the connector. Figure 2 Current Measurement Connector i.MX31 PDK 1.5 Power Measurements Application Note, Rev. 1.3 Freescale Semiconductor 3 Figure 3 provides a detailed view of the connector. Table 2 describes the pin-out. Figure 3 Detail View of the Current Measurement Connector Table 2 Current Measurement Connector Pin-out Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 4 Description Ground SW1 Core and L2 current (1V2_1V6_SW1) VMAIN voltage 1.8V Memories (1V8_SW2A) Ground VMAIN current LI_BATTERY voltage Reserved Ground Reserved 1.8V voltage 1.8V peripherals (EXT_1V8) Ground 3.3V to HDD (HDD_3V3) WALL_5V_IN Wall Supply 5V (WALL_5V_IN) Ground Lithium Battery (LI_BATTERY) Ground Reserved i.MX31 PDK 1.5 Power Measurements Application Note, Rev. 1.3 Freescale Semiconductor 2 Measuring the Current To measure the current, use these steps: 1. Measure the voltage value using a multimeter on the desired pin (current pin ex. PIN6 VMAIN current). The value reflected in the pin is the voltage reading from the MAX4071 chip. 2. To obtain the current value, subtract 1.5 from the voltage measured. 3. Multiple the results by 500. 4. The current value is expressed in mA. Formula The formula for obtaining the current consumption from the MAX4071 readings is: I = (V-1.5) x 500 Where: V is the reading from the connector pin. Example Table 3 provides an example of the current consumption values for a given voltage on the pin. Table 3 Example Current Consumption Voltage Current (mA) 3.5 V 1000 mA 2.5 V 500 mA 1.5 V 0 mA 0.5 V - 500 mA i.MX31 PDK 1.5 Power Measurements Application Note, Rev. 1.3 Freescale Semiconductor 5 How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor Technical Information Center, EL516 2100 East Elliot Road Tempe, Arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.com/support Europe, Middle East, and Africa: Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen, Germany +44 1296 380 456 (English) +46 8 52200080 (English) +49 89 92103 559 (German) +33 1 69 35 48 48 (French) www.freescale.com/support Japan: Freescale Semiconductor Japan Ltd. Headquarters ARCO Tower 15F 1-8-1, Shimo-Meguro, Meguro-ku, Tokyo 153-0064, Japan 0120 191014 or +81 3 5437 9125 [email protected] Asia/Pacific: Freescale Semiconductor China Ltd. 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