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19-1308; Rev 1; 10/98
MAX1660 Evaluation Kit
General Description
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 (SMBusTM) interface. o 4A Max Current, 1% Accuracy o Proven PC Board Layout o Convenient Test Points Provided On-Board o Data-Logging Software o Fully Assembled and Tested
Features
o Measures 4A Currents to 1% Accuracy
Evaluates: MAX1660
Ordering Information
PART MAX1660EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 16 QSOP
Component List
DESIGNATION QTY C1 C2 C3 C4 C5 C6* D1, D20, D21, D22 D23-D26 J1 J2 1 1 1 1 1 0 4 4 1 1 DESCRIPTION 0.33F, 6V ceramic capacitor 10nF, 6V ceramic capacitor 0.1F, 6V ceramic capacitor 4.7nF, 6V ceramic capacitor 10nF, 6V ceramic capacitor 0.33F ceramic capacitor (option) 1N4148-type SOT23 signal diodes 1N5233B-type, 6V, 500mW, axialleaded zener diodes DB25 male right-angle connector Smart battery connector AMP 787259-1 (10.8V key on left) Uninsulated, nickel-plated standard banana jacks E. F. Johnson 108-0740 Unstuffed Red light-emitting diode Logic-level, P-channel, SO-8, single power MOSFET International Rectifier IRF7205 R2, R30-R33 R3, R5 R4, R6 R7, R8 R9, R10, R20, R21, R24, R25, R26 R11 R12* R22, R23, R27, R28, R29, R35 R34 SW1 U1 U2 *User option 5 2 2 2 7 1 0 6 1 1 1 1 R1 1 DESIGNATION QTY Q20, Q21, Q22 3 DESCRIPTION 2N3904 NPN equivalent, SOT23 0.030, 1%, 1W sense resistor IRC LR2512-01-R030-F or Dale WSL-2512 0.030 100, 5%, 1/16W resistors 910k, 1%, 1/16W resistors 75k, 1%, 1/16W resistors 470k, 5%, 1/16W resistors 10k, 5%, 1/16W resistors 1M, 5%, 1/16W resistor 51, 5%, 1/16W resistor (option) 100k, 5%, 1/16W resistors 680, 5%, 1/16W resistor Slide switch Maxim MAX1660EEE 74HC14 hex Schmitt trigger, SO-14
J3, J4 JU1 LED1 M1, M2
2 1 1 2
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.
MAX1660 Evaluation Kit Evaluates: MAX1660
Component Suppliers
SUPPLIER Dale Sense Resistors International Rectifier IRC PHONE (402) 564-3131 (310) 322-3331 (512) 992-7900 FAX (402) 563-6418 (310) 322-3332 (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 3.1TM or Windows 95TM 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.
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.)
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.
Windows 3.1 and Windows 95 are trademarks of Microsoft Corp.
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MAX1660 Evaluation Kit
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.
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.
Evaluates: MAX1660
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).
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.
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 1s of uncertainty, whereas the EV kit software under Windows has an uncertainty of 10,000s. 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.
___________________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
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MAX1660 Evaluation Kit Evaluates: MAX1660
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. 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.
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
Listing 1. Reading 32-Bit Counters
Listing 2. Soft Shutdown
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MAX1660 Evaluation Kit Evaluates: MAX1660
Listing 3. Measuring Offset
_______________________________________________________________________________________
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Evaluates: MAX1660
MAX1660 Evaluation Kit
Figure 1. MAX1660 EV Kit Schematic
R11 1M INT SCL SDA RST DGND SW1 J3 PACK+ JU1 4 4 D1 GPIO 1 1 L 2 R SDA 2 SHDN 15 3 INT SCL 16 R8 470k 1, 2, 3 1, 2, 3 5, 6, 7, 8 M2 IRF7205 M1 IRF7205 5, 6, 7, 8
6
J2
SMART BATTERY CONNECTOR
*
R12 51
CUT HERE R7 470k R9 10k
1 BATT+ 2 N.C. 3 N.C. 4 N.C. 5 BATTR2 100 CMPD4448 1N4148 3 N.C. RST 14 13 12 11 10 9 C1 0.33F DGND R10 10k
U1
4 C3 0.1F 5 AGND ODO BATT VL GND 6 REF 7 ODI 8 OCI CS
MAX1660
OCO
C5 10nF C2 10nF AGND
R1 0.03 1W R5 910k 1% R3 910k 1%
*
C6 0.33F +3V
DGND AGND R6 75k 1% C4 4.7nF AGND AGND R4 75k 1%
DGND
KELVIN GROUND POINT
_______________________________________________________________________________________
DGND *USER OPTION. NOT INSTALLED.
J4
PACK-
J1-18 J1-19 J1-16 J1-17 NO CONNECTS DGND +3V R31 100 U2B U2E 10 11 74HC14 R34 680 74HC14 12 13 U2F INT 4 3 +3V J1-10 D26 6V DGND Q21 1 L R28 100k SDA J1-15 D25 6V DGND D22 J1-4 R30 100 U2A 2 1 +3V CMPD4448 1N4148 R29 100k 2R 3 74HC14 2R 3 1L R26 10k Q22 1 L R22 100k 9 74HC14 U2C 6 74HC14 +3V 5 2R CMPT3904 NPN/2N3904 3 R32 100 LED1 DGND +3V R21 10k 74HC14 R33 100 R23 100k U2 p14 p7 +3V GND J1-21 J1-25 +3V RST LOGIC SUPPLIES J1-20 J1-24 R35 100k J1-23
J1-22
J1-5
J1-13
J1-1
J1-8
J1-6
J1-9
J1-7
J1-14
J1-11 D24 6V DGND
Figure 1. MAX1660 EV Kit Schematic (continued)
3 R25 10k DGND U2D 8 GPIO D23 6V 3 1 L R27 100k 2R CMPT3904 NPN/2N3904 DGND 3 SCL R24 10k Q20 R20 10k CMPT3904 NPN/2N3904 DGND
D21
J1-3
1
L
2R
CMPD4448 1N4148
J1-12
D20
J1-2
1L
2R
Evaluates: MAX1660
_______________________________________________________________________________________
CMPD4448 1N4148
MAX1660 Evaluation Kit
7
MAX1660 Evaluation Kit Evaluates: MAX1660
1.0"
Figure 2. MAX1660 EV Kit Component Placement Guide
8
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MAX1660 Evaluation Kit Evaluates: MAX1660
1.0"
Figure 3. MAX1660 EV Kit PC Board Layout--Component Side
_______________________________________________________________________________________
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MAX1660 Evaluation Kit Evaluates: MAX1660
1.0"
Figure 4. MAX1660 EV Kit PC Board Layout--Solder Side
10
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MAX1660 Evaluation Kit
NOTES
Evaluates: MAX1660
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MAX1660 Evaluation Kit Evaluates: MAX1660
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 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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