19-1308; Rev 1; 10/98 MAX1660 Evaluation Kit The MAX1660 evaluation kit (EV kit) is an assembled surface-mount demonstration board. The EV kit embodies the typical application circuit shown in Figure 8 of the MAX1660 data sheet. Additional circuitry allows an IBM-compatible personal computer to use its parallel port to emulate an Intel System Management Bus (SMBus™) interface. Features ♦ Measures 4A Currents to 1% Accuracy ♦ 4A Max Current, 1% Accuracy ♦ Proven PC Board Layout ♦ Convenient Test Points Provided On-Board ♦ Data-Logging Software ♦ Fully Assembled and Tested Ordering Information PART TEMP. RANGE MAX1660EVKIT 0°C to +70°C IC PACKAGE 16 QSOP Component List DESIGNATION QTY DESCRIPTION C1 1 0.33µF, 6V ceramic capacitor C2 1 10nF, 6V ceramic capacitor C3 1 0.1µF, 6V ceramic capacitor C4 1 4.7nF, 6V ceramic capacitor C5 1 10nF, 6V ceramic capacitor C6* 0 0.33µF ceramic capacitor (option) D1, D20, D21, D22 4 1N4148-type SOT23 signal diodes D23–D26 4 1N5233B-type, 6V, 500mW, axialleaded zener diodes J1 DESIGNATION QTY DESCRIPTION Q20, Q21, Q22 3 2N3904 NPN equivalent, SOT23 R1 1 0.030Ω, 1%, 1W sense resistor IRC LR2512-01-R030-F or Dale WSL-2512 0.030Ω R2, R30–R33 5 100Ω, 5%, 1/16W resistors R3, R5 2 910kΩ, 1%, 1/16W resistors R4, R6 2 75kΩ, 1%, 1/16W resistors R7, R8 2 470kΩ, 5%, 1/16W resistors R9, R10, R20, R21, R24, R25, R26 7 10kΩ, 5%, 1/16W resistors R11 1 1MΩ, 5%, 1/16W resistor R12* 0 51Ω, 5%, 1/16W resistor (option) R22, R23, R27, R28, R29, R35 6 100kΩ, 5%, 1/16W resistors 1 DB25 male right-angle connector J2 1 Smart battery connector AMP 787259-1 (10.8V key on left) J3, J4 2 Uninsulated, nickel-plated standard banana jacks E. F. Johnson 108-0740 JU1 1 Unstuffed LED1 1 Red light-emitting diode R34 1 680Ω, 5%, 1/16W resistor SW1 1 Slide switch 2 Logic-level, P-channel, SO-8, single power MOSFET International Rectifier IRF7205 U1 1 Maxim MAX1660EEE U2 1 74HC14 hex Schmitt trigger, SO-14 M1, M2 *User option SMBus is a trademark of Intel Corp. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. Evaluates: MAX1660 General Description Evaluates: MAX1660 MAX1660 Evaluation Kit Component Suppliers SUPPLIER PHONE FAX Dale Sense Resistors (402) 564-3131 (402) 563-6418 International Rectifier (310) 322-3331 (310) 322-3332 IRC (512) 992-7900 (512) 992-3377 *Please indicate that you are using the MAX1660 when contacting these suppliers. _________________________Quick Start Equipment Required Before you begin, you will need the following equipment: • • A battery pack An appropriate charger • • An appropriate load An IBM PC-compatible computer running Windows 3.1™ or Windows 95™ A spare parallel printer port (this is a 25-pin socket on the back of the computer) A standard 25-pin, straight-through, male-to-female cable to connect the computer’s parallel port to the Maxim EV kit (optional). Or, the EV kit can be plugged directly into the parallel printer port. • • Procedure 1) Connect the battery pack to the board at connector J2. Total battery-pack voltage should be within the 4V to 28V range accepted by the MAX1660. The battery cells may be of any rechargeable chemistry, such as NiCd, NiMH, or Li-Ion. The battery pack will later be charged and discharged through the PACK+ and PACK- terminals; however, leave PACK+ unconnected until the software is started. Powering the EV kit with a power supply that is not isolated from the computer creates a ground loop, degrading measurement accuracy by 50% or more. 2) Connect the board to the computer’s parallel printer port. The parallel port is typically labeled LPT or PRINTER. To avoid damaging the EV kit or your computer, make sure you are using the parallel printer port and not a 25-pin SCSI port or any other connector that is physically similar to the 25-pin parallel printer port. 3) The MAX1660.EXE software program can be run from the floppy or from a hard drive. Simply use the Windows program manager to run the program. If desired, you may use the INSTALL.EXE program to copy the files and create icons for them in the Windows 3.1 Program Manager (or the Windows 95 Start Menu). 4) Start the MAX1660 program by opening its icon in the Program Manager (or Start Menu). 5) The program prompts you to select the correct parallel port. An auto-detect routine attempts to identify the correct port and highlights it as the default choice. 6) Apply the load or charger and observe the charge or discharge current readings on the main window display. Detailed Description _________________________of Software The battery pack can be charged and discharged through the PACK+ and PACK- terminals. When a load is connected across the PACK+ and PACK- terminals, the discharge current is measured and displayed. If the load current exceeds the overcurrent trip threshold, MOSFET M1 turns off, disconnecting the load. Main Display The charge and discharge counters are automatically displayed in either decimal or hexadecimal, along with the corresponding charge count and the calculated current values. The Clear Counters button commands the MAX1660 to clear its charge and discharge counters, and it also restarts the integration timer. The display is automatically updated at the rate selected by the Integration Time control. This automatic update can be turned off by unchecking the Automatically Update Displays check-box. The INT signal is checked several times per second, and the Interrupt box indicates if it is low. To clear the interrupt, click on the Clear Interrupt button. When the Fuel Gauge Off control is activated, the software automatically activates Disconnect Battery and Disconnect Load to protect the battery. Unchecking either Disconnect Battery or Disconnect Load automatically unchecks Fuel Gauge Off. The Calibrate check-box controls the OFFSETMEAS bit in the configuration word. When active, the Coulomb counter is disconnected from the sense resistor, revealing the offset voltage (which appears as an offset current in this display.) Windows 3.1 and Windows 95 are trademarks of Microsoft Corp. 2 _______________________________________________________________________________________ MAX1660 Evaluation Kit Accuracy Limitations under DOS To allow evaluation of the MAX1660 without the currentmeasurement errors caused by Windows, use the DOS1660 program. This menu-driven program provides rudimentary access to the MAX1660, with stable timing. An oscilloscope can be used to observe a read diagnostic strobe that appears on pins 5 and 13 of the parallel port. To start the DOS1660 program, click on the DOS1660 menu item, or exit Windows and run DOS1660.EXE. Sense-Resistor Value The effect of different current-sense resistors can be shown by selecting the Sense Resistor command from the MAX1660 menu. This command opens a window that displays the assumed sense resistor value, as well as the conversion gain calculations resulting from that value. For correct current display, the sense-resistor value should match the actual value of RCS (which is R1 on the EV kit board). SMBus Menu The SMBus menu allows individual SMBus operations to be performed. The main window continues independently performing its own SMBus transactions unless the Automatic Update Displays box is unchecked. The SMBus dialog boxes accept numeric data in binary, decimal, or hexadecimal. Hexadecimal numbers should be prefixed by $ or 0x. Binary numbers must be exactly 8 or 16 digits. Accuracy Limitations under Windows Charge or discharge current can be measured by sampling the counter value at intervals and calculating: Current = (increase in counter value) / (time interval in seconds x conversion gain) When calculating charge or discharge current, there is an inherent measurement error of one count or less in each integration period, due to fractional counts during the integration period. There is also a processordependent measurement uncertainty in the integration time. A crystal-controlled microcontroller with no other tasks can easily have less than 1µs of uncertainty, whereas the EV kit software under Windows has an uncertainty of 10,000µs. Longer integration time reduces this measurement error. The current measurement error due to timing jitter is displayed in the main window under the heading “uncertainty”. To accurately measure load current, the program must accurately measure the time interval between counter reads. The counter value is latched on the falling edge of the ACK clock pulse during the SMBusReadWord (address 0x83, command 0x82). Refer to the MAX1660 data sheet. Detailed Description ________________________of Hardware U1, the MAX1660, is a digitally controlled fuel-gauge interface that accurately monitors charge and discharge currents. C6 and C1 bypass the power supply. R1 is the noninductive current-sense resistor. It is Kelvin connected to reduce error at high currents. R3–R6 set the overcurrent trip thresholds. MOSFETs M1 and M2 are used by the overcurrent protection circuitry to interrupt the discharge and charge paths, respectively. D1 and R11 would typically be used by a microcontroller to implement a hard-shutdown mode. Refer to the MAX1660 data sheet for more discussion of the standard application circuit. The SMBus interface circuitry consists of J1, D20–D26, LED1, Q20, Q21, Q22, R20–R35, and U2. This part of the circuit provides the 2-wire clock and data interface, as well as a GPIO output (used for shutdown control) and an interrupt input. When the board is not plugged into an IBM PC parallel port, the clock and data lines can be driven externally, and the GPIO output is controlled by switch SW1. The LED lights up whenever the interrupt signal is at a logic-low level. If desired, the EV kit can be driven with a user-supplied SMBus 2-wire interface. Connect it to the DGND, SCL, and SDA pads on the board. ___________________Interface Details A complete smart-battery solution is far beyond the scope of this manual; however, there are a few details that the software designer must know in order to successfully use this device. Reading 32-Bit Counters To accurately measure supply current, the program must accurately measure the time interval between counter reads. During the read-word protocol, begin the integration time at the falling edge of the ninth clock pulse of the command byte. Not counting the start condition, this is the 18th falling edge of the clock during SMBusReadWord (address 0x8e, command 0x82). _______________________________________________________________________________________ 3 Evaluates: MAX1660 Register Display The MAX1660 register values can be displayed in 32-bit binary format by selecting Registers from the MAX1660 menu. This command opens a window that updates five times per second, independent of the main display’s integration time control. The Compare Register group in the main window selects the charge or discharge register. Evaluates: MAX1660 MAX1660 Evaluation Kit When reading the 32-bit charge or discharge counter value, read the low word first (command 0x82) followed by the high word (command 0x83). This sequence latches the counter value and prevents the data from being corrupted if there is a 16-bit carry during the read operation. See Listing 1. Soft Shutdown When turning the fuel gauge off (SOFTSHDN = 1), disconnect the battery (OCHI = 1, ODLO = 0) and the load (ODHI = 1, ODLO = 0). When the fuel gauge is inactive, the overcurrent protection is disabled. Leaving the battery or the load connected with the fuel gauge off can destroy the FETs if a short-circuit condition occurs. See Listing 2. Optional Offset Calibration The MAX1660’s input offset is quite low; however, it can be measured by setting OFFSETMEAS = 1. When offset-measurement mode is active, the charge and discharge currents cannot be monitored, so disconnect the battery (OCHI = 1, OCLO = 0) and the load (ODHI = 1, ODLO = 0). See Listing 3. Listing 1. Reading 32-Bit Counters Listing 2. Soft Shutdown 4 _______________________________________________________________________________________ MAX1660 Evaluation Kit Evaluates: MAX1660 Listing 3. Measuring Offset _______________________________________________________________________________________ 5 6 SMART BATTERY CONNECTOR R1 0.03Ω 1W 1 BATT+ 2 N.C. 3 N.C. 4 N.C. 5 BATT- Figure 1. MAX1660 EV Kit Schematic _______________________________________________________________________________________ PACK- J4 KELVIN GROUND POINT DGND AGND J2 C5 10nF R2 100Ω GPIO INT R L AGND R6 75k 1% R5 910k 1% 3 R4 75k 1% R3 910k 1% C2 10nF CMPD4448 1N4148 2 1 D1 AGND C3 0.1µF INT JU1 SW1 AGND CS N.C. AGND C4 4.7nF GND 8 OCI BATT ODO OCO RST VL MAX1660 U1 SDA SCL ODI 7 6 REF 5 4 3 2 SHDN 1 DGND R11 1M 9 10 11 12 13 14 15 16 SCL SDA RST C1 0.33µF R10 10k * 4 R12 51Ω R8 470k M2 IRF7205 C6 0.33µF DGND * R7 470k 4 M1 IRF7205 DGND +3V 1, 2, 3 5, 6, 7, 8 *USER OPTION. NOT INSTALLED. DGND R9 10k CUT HERE 1, 2, 3 5, 6, 7, 8 J3 PACK+ Evaluates: MAX1660 MAX1660 Evaluation Kit J1–2 J1–12 J1–3 3 3 CMPD4448 1N4148 2 R 1 L D20 CMPD4448 1N4148 2 R L D21 J1–14 J1–7 1 J1–9 J1–6 J1–11 J1–8 R24 10k R25 10k R27 100k DGND D23 6V R30 100Ω DGND R28 100k R31 100Ω DGND D24 6V NO CONNECTS J1–17 J1–16 2 L Q20 74HC14 U2A CMPT3904 NPN/2N3904 2 R 1 Q21 74HC14 CMPT3904 NPN/2N3904 L 2 R 1 4 U2B 1 3 3 3 +3V +3V p7 GND R21 10k J1–10 DGND R20 10k J1–4 D22 3 SCL CMPD4448 1N4148 2 R 1 L SDA DGND D26 6V R26 10k J1–15 J1–21 p14 +3V U2 J1–20 LOGIC SUPPLIES R29 100k DGND R33 100Ω 10 L Q22 CMPT3904 NPN/2N3904 2 R 1 11 3 R32 100Ω J1–5 +3V DGND D25 6V 74HC14 U2E J1–25 J1–24 J1–23 J1–19 R22 100k LED1 DGND 6 U2C 13 9 5 74HC14 U2D +3V 74HC14 74HC14 R34 680Ω 12 U2F R35 100k 8 R23 100k RST J1–13 GPIO +3V INT +3V Evaluates: MAX1660 J1–1 J1–22 J1–18 MAX1660 Evaluation Kit Figure 1. MAX1660 EV Kit Schematic (continued) _______________________________________________________________________________________ 7 Evaluates: MAX1660 MAX1660 Evaluation Kit 1.0" Figure 2. MAX1660 EV Kit Component Placement Guide 8 _______________________________________________________________________________________ MAX1660 Evaluation Kit Evaluates: MAX1660 1.0" Figure 3. MAX1660 EV Kit PC Board Layout—Component Side _______________________________________________________________________________________ 9 Evaluates: MAX1660 MAX1660 Evaluation Kit 1.0" Figure 4. MAX1660 EV Kit PC Board Layout—Solder Side 10 ______________________________________________________________________________________ MAX1660 Evaluation Kit ______________________________________________________________________________________ Evaluates: MAX1660 NOTES 11 Evaluates: MAX1660 MAX1660 Evaluation Kit NOTES 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.