General Description
The MAX6902 evaluation system (EV system) consists
of a MAX6902 evaluation kit (EV kit) and a companion
Maxim SMBusTM interface board.
The MAX6902 EV kit is an assembled and tested PC
board that demonstrates the MAX6902 SPITM bus real-
time clock (RTC). This EV kit is intended to demonstrate
the functionality and features of the MAX6902 RTC. It is
not designed to exercise the MAX6902 at its maximum
SPI bus interface speed. A typical bus interface speed
is in the 90kHz range and depends upon the operating
system and computer used.
The Maxim SMBus interface board (MAXSMbus) allows
an IBM-compatible PC to use its parallel port to emulate
the SPI, 3-wire, and SMBus (2-wire) interfaces.
Windows 95/98
-compatible software provides a user-
friendly interface to exercise the features of the
MAX6902. (Note: Windows NT/2000 requires additional
driver software; contact factory.) The program is menu
driven and offers a graphic interface with control but-
tons and status display.
Order the complete EV system (MAX6902EVSYS) for
comprehensive evaluation of the MAX6902 using a PC.
Order the EV kit (MAX6902EVKIT) if the MAXSMbus
module has already been purchased with a previous
Maxim EV system, or for custom use in other C-based
systems.
SMBus is a trademark of Intel Corp.
SPI is a trademark of Motorola, Inc.
Windows is a registered trademark of Microsoft Corp.
Features
o Proven PC Board Layout
o Low-Voltage Operation
o Supply Current Monitoring
o Fully Assembled and Tested
o Easy-to-Use Menu-Driven Software
o Includes: Windows 95/98-Compatible Software
(3.5in Floppy Disk) and Demo PC Board
Evaluates: MAX6902
MAX6902 Evaluation System/Evaluation Kit
________________________________________________________________ Maxim Integrated Products
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19-2147; Rev 0; 8/01
MAX6902EVKIT Component List
Ordering Information
DESIGNATION
QTY
DESCRIPTION
C1, C2, C3, C6
4
0.1F, 16V X7R ceramic
capacitors (0603)
Taiyo Yuden EMK107BJ104KA or
Murata GRM39X7R104K016 or
TDK C1608X7R1C104K
C4, C5
2
10F, 35V capacitors
Al Electrolytic
J1
1
2
10 right-angle female
receptacle
JU1, JU2
2
2-pin headers
JU3JU7
0
Not installed
R1
1
49.9k
1% resistor
DESIGNATION
QTY
DESCRIPTION
R2
1
470k
5% resistor
U1
1
MAX6902EKA (8-pin SOT23) RTC
U2
1
MAX1840EUB (10-pin MAX) level
translator
U3
1
MAX3370EXK (SC70) level
translator
U4
1
MAX1615EUK (5-pin SOT23) linear
voltage regulator
Y1
1
32.768kHz quartz crystal, 12.5pF,
20ppm
ECS, Inc. ECS-3X8
FOX Electronics NC38
Vishay Dale XT38T
Y2
0
Not installed
PART
TEMP. RANGE
INTERFACE TYPE
MAX6902EVKIT
0C to +70C
User supplied
MAX6902EVSYS
0C to +70C
MAXSMBus
Note: The MAX6902 EV kit software is provided with the
MAX6902EVKIT. However, to use the software, the MAXSMbus
board is required to interface the EV kit to the computer.
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Evaluates: MAX6902
MAX6902 Evaluation System/Evaluation Kit
2
________________________________________________________________________________________
Quick Start
Required Equipment
Before you begin, the following equipment is needed:
Maxim MAX6902EVKIT and MAXSMbus interface
board
12VDC power supply (any supply voltage between
+9V and +15V is acceptable)
Computer running Windows 95 or 98
Spare parallel port
25-pin I/O extension cable
Procedure
1) Carefully connect the boards by aligning the 20-pin
connector of the MAX6902 EV kit with the 20-pin
header of the MAXSMbus interface board. Gently
press them together. The two boards should be
flush against each other.
Do not turn on the power until all connections are
made.
2) Connect the 25-pin I/O extension cable from the
computer's parallel port to the MAXSMbus board.
The EV kit software uses a loopback connection to
confirm that the correct port has been selected.
3) Install the EV system software on your computer by
running the INSTALL.EXE program on the floppy
disk. The program files are copied and icons are
created for them in the Windows Start menu.
4) Ensure that the jumper settings are in the default
position (Table 1).
5) Connect the 12VDC power supply to the
MAXSMbus board between POS9 and GND.
Voltage for the MAX6902 ICs comes from the
MAXSMbus board.
6) Start the program by opening its icon in the Start
menu.
7) Click on the Set from computer's clock button to
write the current time of day into the MAX6902.
8) Observe the difference between the computer's
time and the MAX6902 time. The offset is calculated
by Offset = RTC time - PC time. In general, the RTC
keeps more accurate time than the PC. To deter-
mine long-term accuracy of the RTC, it must be set
by and checked against an accurate time source.
The easiest way to do this using the MAX6902 eval-
uation software is to use an Internet time service to
set the PC clock and then set the RTC from the PC
clock. This Internet time service can then be used to
update accurately the PC clock regularly for an
accurate comparison of the RTC against a known
time standard. The National Institute of Standards
and Technology (NIST) offers such an Internet time
service without charge (see www.boulder.nist.gov/
timefreq/service/its.htm).
Note: The MAX6902EVSYS may be unplugged from the
parallel port for long-term drift testing.
Detailed Description
of Hardware
The MAX6902 (U1) is a real-time clock with RAM. The
two level translators, MAX1840 (U2) and MAX3370
(U3), are not required for normal operation of the
MAX6902, but allow operation at supply voltages down
to +2V, while still communicating with the MAXSMbus
board, which is using +5V logic levels. See Figure 7
and refer to the MAX6902 data sheet.
Measuring Timekeeping Supply
Current
The MAX6902 is in standby mode whenever no com-
mands are being sent. To measure the timekeeping
supply current drawn in standby mode, first ensure that
the main screen's Cyclic Burst Read checkbox is not
checked, remove the shunt from jumper JU2, and mea-
sure the voltage across resistor R1. A voltage drop of
10mV represents 200nA of timekeeping supply current.
For active bus operation (serial bus activity), replace
shunt JU2 to prevent excessive voltage drop across
resistor R1.
Surface-Mount Crystal
The EV kit comes with a 1.1mm cylindrical tuning fork
crystal; however, the PC board layout accommodates
an optional surface-mount crystal. Only one crystal may
be used.
MAX6902EVSYS Component List
Component Suppliers
PART
QTY
DESCRIPTION
MAX6902EVKIT
1
MAX6902 evaluation kit
MAXSMBUS
1
Interface board
SUPPLIER
PHONE
FAX
Murata
770-436-1300
770-436-3030
Taiyo Yuden
800-348-2496
847-925-0899
TDK
847-803-6100
847-390-4405
Note: Please indicate you are using the MAX6902 when contact-
ing these manufacturers.
MAXSMbus Connector
The MAXSMbus board connects to the MAX6902 EV kit
in accordance with Table 2.
Evaluation of the MAX6902 at
a Lower Voltage
To evaluate the MAX6902 at a lower voltage, remove
the shunt from jumper JU1 and apply the desired volt-
age to the VL pad.
EV Kit Stand Alone
The MAX6902 EV kit can be connected to a different
SPI interface with or without level translation.
To connect with level translation, use the pads labeled
X_DOUT, X_DIN, X_SCLK, and X_CS. Cut the trace
shorting jumper JU7 and connect the SPI interface
logic voltage to the VCC pad. Remove the shunt from
jumper JU1 and apply the desired voltage for the
MAX6902 to the VL pad. The voltage applied to VL
must be less than or equal to VCC. Applying a higher
voltage to VL damages the MAX3370 level translator.
To connect without level translation, cut the traces
shorting JU3, JU4, JU5, and JU6 and use the pads
labeled DOUT, DIN, SCLK, and CS. Remove the shunt
from jumper JU1 and connect the SPI interface logic
voltage to the VL pad to power the MAX6902.
Troubleshooting
Problem: Unable to communicate while measuring
supply current.
Jumper JU2 must be closed to enable communication.
Problem: Initial date POR value of RTC is 01-JAN-2070.
RTC evaluation software was started. RTC time was set
from computer clock. RTC was powered down. RTC
evaluation software remained running and then RTC
was powered back up. RTC evaluation software only
reads the Century register when time is set from the
computer clock or when the software is initially
launched. Stop Cyclic Burst Read. Do a single read of
the Century register. Continue by starting the Cyclic
Burst Read.
Detailed Description
of Software
The evaluation software provides access to all regis-
ters. The main timekeeping registers appear in the
main screen, with other screens accessible from the
View menu. To write to a single register, click on the
appropriate register select button, set the desired
value, and then click the Write button. To read a regis-
ter, click on the appropriate register select button, and
then click the Read button. Cyclic Burst Read should
be disabled before a read or write to a single register.
Evaluates: MAX6902
MAX6902 Evaluation System/Evaluation Kit
_______________________________________________________________________________________
3
Table 1. Jumper Functions
*Asterisk indicates default configuration.
JUMPER
POSITION
FUNCTION
*Closed
V
L
= +5V
JU1
Open
User-supplied V
L
+5V
*Closed
Supply current-sensing resistor
R1 is shorted, enabling
communication with the real-time
clock.
JU2
Open
Timekeeping supply current can
be estimated by measuring
voltage across R1.
Communication is not possible
in this state.
Table 2. MAXSMbus Connector Signals
Note: Odd-numbered pins are on the outer row. Even-numbered
pins are on the inner row.
PIN
CONNECTOR P1 ON
THE
MAXSMbus BOARD
CONNECTOR J1 ON
THE
MAX6902 EV KIT
1
+5V
No Connection
2
GND
Ground
3
SDA
X_DOUT
4
GND
Ground
5
GND
Ground
6
GND
Ground
7
SCL
X_SCLK
8
GND
Ground
9
SMBSUS
X_CS
10
GND
Ground
11
ALERT
No connection
12
GND
Ground
13
ALERT2
No connection
14
GND
Ground
15
OUTA
X_DIN
16
GND
Ground
17
OUTB
No connection
18
GND
Ground
19
GND
Ground
20
RAW PWR
+9V
Evaluates: MAX6902
Main Screen
The Read button reads the most recently selected time-
keeping register. The Write button writes the most
recently selected timekeeping register. The Burst Read
button performs a Burst Read from the timekeeping
registers (except Century). The Burst Write button per-
forms a Burst Write to the timekeeping registers (except
Century). The Set from computer's clock button writes
the PC's time into the MAX6902. The Cyclic Burst Read
checkbox tells the software to perform a Burst Read
from the timekeeping registers, at a rate of approxi-
mately 4 times per second. Updates are shown in the
register display, along with the difference between
MAX6902 time and the host PC's time.
Note: Cyclic Burst Read should be disabled before a
read or write to a single register.
The Hour register setting can be switched from 12hr
format to 24hr format by clicking the -->24 button.
RAM Screen
The Single Read button reads the most recently select-
ed RAM location. The Single Write button writes the
most recently selected RAM location. The Burst Read
button performs a Burst Read from the entire RAM. The
Burst Write button performs a Burst Write to the RAM.
Normally, all 31 locations are read; but the Burst Write
length can be reduced. Burst Write always begins with
RAM location 0. The Preset Data button performs a
Burst Write to the RAM, setting all data to the same
value. Note: Cyclic Burst Read should be disabled
before reading or writing to RAM. Figure 2 is the RAM
Screen.
Alarm Thresholds Screen
The Read button reads the most recently selected
alarm threshold register. The Write button writes the
most recently selected alarm threshold register.
The Hour register setting can be switched from 12hr
format to 24hr format by clicking the -->24 button. The
time format should be the same in both the Alarm
threshold and timekeeping registers. Note: Cyclic Burst
Read should be disabled before a read or write to a
single register. Figure 3 is the Alarm Thresholds screen.
MAX6902 Evaluation System/Evaluation Kit
4
_______________________________________________________________________________________
Figure 1. Main Screen
Evaluates: MAX6902
MAX6902 Evaluation System/Evaluation Kit
_______________________________________________________________________________________
5
Figure 2. RAM Screen
Figure 3. Alarm Thresholds Screen
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