1
RTC EVB
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Intersil RTC Devices Supported
Introduction
This evaluation board provides a platform for testing Intersil Real Time Clock (RTC) devices. Device features include a crystal oscillator, clock and date counters, voltage monitoring and reset, watchdog timer, and alarms. The ISL1209/19/21 devices include an event-detection and timestamp feature for recording the time of an event. The ISL12020/21 devices feature a temperature sensor and temperature
compensation.
The evaluation board provides a platform to test all of these functions, as well as evaluate device performance criteria, such as long-term clock accuracy. Hardware options such as battery and crystal types can also be tested. The software is designed to allow easy setup and monitoring of all major device functions. The two-piece construction utilizing a motherboard and a daughtercard enables the board and software to operate the RTC device residing on a remote board.
Operation and Overview of the RTC Evaluation Board
Hookup and Power CONNECTIONS
The eval board consists of a motherboard and daughtercard and these need to be connected together. The evaluation board uses a USB connection to communicate and drivers must be installed on each PC that talks to the RTC eval board. A USB cable, with type A and B connectors on the ends, is required to hook up the board to a PC. The cable should be connected to the PC first and then to the eval board. Once connected, the POWER LED will illuminate
indicating +5V power is available from the USB cable and the USB has a connection.
POWERING DOWN
The motherboard contains backup power, consisting of batteries or a supercap. When powering down, the
daughtercard will operate off the backup source determined by J4 (after the VCC voltage discharges from the VCC supply capacitors). If the user wishes to totally power down the RTC device once VCC is removed, then either remove the daughtercard from the motherboard or set JP2 to GND.
Keep in mind there is a decoupling capacitor on the daughtercard (0.1µF) which must discharge fully before the RTC device stops operating. This discharge time can be up to one second when using a VCC of 5V. Note that when powered down, the RTC board cannot be monitored by the RTC software.
Installing the RTC Software and USB Drivers
USB SOFTWARE AND DRIVERS SETUP INSTALL BASE SOFTWARE AND DRIVERS
• Insert CD in the PC. Do not plug in the RTC USB eval board yet.
• Double click Setup.exe
• Click to agree on license window, then click to install.
• AFTER software install, plug the board in and it should bring up the hardware installation wizard window.
• When asked for the location of drivers, use the CD drive.
• Click to do the installation of drivers and then finish.
The install program will place the RTC evaluation program (RTC.exe) in this location:
C:\Program Files\Intersil\RTC Eval
INSTALL SOFTWARE UPDATE FOR LATEST DEVICES On the CD, open the folder “USB_RTC_Update_V3.xx”
which contains the update executable file. Double click on that file and follow the instructions on the screen.
After installation it is a good idea to make a shortcut on your desktop to allow quick startup of the program.
Using the Software
To start the program, double click on RTC.exe and the opening window should appear as in Figure 1. This is the Setup screen as indicated on the tab. At the bottom of the window there are status messages for the USB connection.
The center message will state if USB is active or inactive, and next to it will be the connect time if the USB RTC board has been plugged in.
TABLE 1.
With EEPROM No EEPROM No EEPROM
ISL12024 ISL1208 ISL12020
ISL12025 ISL1209 ISL12020M
ISL12026 ISL1218 ISL12022M
ISL12027 ISL1219 ISL12022
ISL12028 ISL1220 ISL12032
ISL12029 ISL1221
Application Note February 19, 2008
FIGURE 1. EVALUATION SOFTWARE GUI MAIN TAB There are multiple tabs for different setup and RTC
functions. The icons at the top will stay visible independent of the tab chosen, as well as the right section displaying polling data.
SETUP TAB
There are 3 sections to the Setup screen, plus the display section. The left section is for device selection, with a pulldown window to select which Intersil RTC device daughtercard is connected. Details of the selected device features are displayed. Selecting a device here will also set the content of the other tabs to options for that device. Note that the ISL12022 selection ALSO supports the ISL12022M and ISL12020M modules.
The middle section has 5 functions. Vcc enabled is the status of the Vcc switch on the motherboard. Clicking the window here will enable or disable Vcc to the daughtercard.
The switch icon in the top icon bar will do the same. The I2C buss speed can be selected, either 100kHz or 400kHz. The temp sensor type can be selected (RTC daughtercards have either LM75 or LM76) and the sensor temperature output can be calibrated, the offset selected in that window is reflected in the temp sensor output display on the right.
The Eval Board Select function can select among multiple Intersil eval boards connected to a PC, and should be set to usb_rtc. PC time format controls how the PC time window displays time, either 12 or 24 hour (military) format.
The right section is the status display and clear section. The relevant status bits for the device are displayed as lights in the upper section, and those bits can be cleared using the buttons in the lower section.
The display section appears regardless of tab selected and contains the following windows:
• PC Time - The time kept on the PC, displayed all the time
• RTC Time - the monitored RTC device time, displayed while Polling is enabled
• RTC Deviation - the delta between RTC device time and PC time
• PC date - the current date kept on the PC, displayed all the time
• RTC date - the monitored RTC date, displayed while polling is enabled.
• Temperature - the current reading of the temperature sensor, displayed while polling is enabled. If there is no temperature sensor the window will be blank. The Intersil RTC device daughtercards use the LM75 device. Older daughtercards may have used the LM76 device. The temperature section allows selection of either device.
SET CLOCK TAB
This tab contains 3 sections, Time and Data, Adjust RTC from PC Clock, and Adjust RTC from Time and Date Selection. The display section on the far right should have polling enabled in order to check the RTC time and date when doing Set Clock functions.
• Time and Data Selection - allows selection of the time/date that can be written to the RTC device. Includes 12/24 hour format selection.
• Adjust RTC from PC Clock - two options. Write to the RTC device the current PC time/date, or write to the PC clock with the current RTC time/date. Note that if the latter is chosen, the current PC time and date will be lost.
• Adjust RTC from Time and Data - two options. Set RTC Date and Time will take the date and time from the Time
and Data selection window on the left and write to the RTC device. Second selection is to write the current RTC time to the Data Selection window.
REGISTERS TAB
This tab enables reading and writing to each of the registers in the RTC device. The pulldown window at top will allow selection of one of the list of the different register groups (the groups will correspond to those of the device chosen in the Setup Tab).
For writing, it is possible to change individual bits using the cells in each register, or to change the hex value in the column on the left. After changing the register value, the
“Write” button for the register must be clicked under the Byte Operation column, or the page write at the bottom can be used.
For reading, the individual registers can be read or the page read at the bottom can be used.
Note that performing operations in the other tabs will change the registers in a device, and those results can be read directly in the Registers tab. Also, changes made in the Registers tab will be reflected in the tabs for the corresponding functions.
GRAPH TAB
The program is able to record continuous time
measurements of the RTC deviation from PC Clock and the board temperature and create a plot of the results. Time frames from a few minutes to many days are possible. First select the deviation range in pulldown window in the lower right corner for the time scale. The Temperature Range and Time Base (measurement time length) should also be set as desired from their pulldown windows.
Set the RTC time from the PC time as described above. This will insure the PC time is close to the RTC time to begin recording.
To begin recording, check the “Enable Polling” box in the Data display on the right. The graph will automatically record data as long as the polling function is enabled. Graphing will stop when polling is disabled and will start again where the data left off when enabled again. If you wish to collect new data, then click the “Restart” button.
Data will be recorded periodically until the end of the time frame selected or until polling is stopped. Note that multiple samples are recorded and averaged before being plotted on the chart recorder.
The raw data can be saved to a file for other uses such as in a spreadsheet. Choose a file folder using the folder icon in the menu bar. Then use the “save file” icon to choose a file name and save.
The start time is shown at the bottom left of the screen for reference. Note that for long recordings of deviation, it is advisable to use a PC program that automatically updates
the PC time, such as that available from NIST http://www.boulder.nist.gov/timefreq/service/its.htm.
INTERRUPT TAB
This tab contains control for the Frequency Output pin. The pulldown window allows selection of frequency for the device chosen. There is also a check box for frequency output in battery backup mode. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button.
ALARM TAB
The left side of the window contains the controls to enable the alarm and alarm mode, as well as pulldowns to select the alarm time/date match conditions. Note that the hours pulldown contains entries for both Military and regular time, and this must correspond to the time display chosen for the RTC registers. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button. The right side window contains the status for the alarm.
EVENT TAB (ISL1209, 1219, 1221 ONLY)
This tab controls all the Event and Timestamp functions, when available. The left side of the window contains the control register bits to enable the event detection and set the timing and hysteresis functions. Controls for the event detect in battery mode, halt RTC on event, and the current source disable are included. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button. The right side of the window includes the status indicator, and also a window to show the timestamp register, if available (not on ISL1209).
CRYSTAL COMP TAB
This tab includes control checkboxes for the 3 bits of control for the RTC compensation features. ATR, DTR, and Battery Mode ATR controls are included. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button.
Hardware and Software Detailed Descriptions
USB RTC Evaluation Board - General Description The evaluation board consists of the motherboard and daughtercard. The motherboard contains all the main support functions for the RTC device, including:
• Microcontroller with USB interface for communicating with the PC and the RTC.
• I2C Buffer IC for allowing variable I2C pullup voltages
• 5V board supply from the USB, and a regulated 3.3V supply.
• Connectors for the USB interface and the daughtercard.
• A 100uF supercapacitor, a 3.3V rechargeable lithium battery, and a socket for a CR1220 3V lithium coincell battery for backup power.
• Jumpers for selecting which backup battery or
supercapacitor, and also for selecting the VCC voltage of 5V or 3.3V.
• A MOSFET switch controlled by the microcontroller which disconnects the VCC supply from the daughtercard for backup testing.
• Testpoints for monitoring the SCL and SDA lines plus ground.
The daughtercard contains the Intersil RTC device, crystal, temperature sensor IC, decoupling capacitor, and pullup resistor for the open drain output. Daughtercards with event detect IC’s also contain an event detect switch plus jumper for selecting the event input connection. For individual daughtercard schematics, contact Intersil.
DAUGHTERCARD ON/OFF CONTROL
The normally open switch icon in the menu bar controls whether VCC power is applied to the daughtercard. Click on the icon once to shut off VCC power and the icon will show the open switch. Click again on the icon to reapply VCC power and the icon will close the switch. Note that when VCC power is turned off, the RTC device will operate from backup power selected by J4 on the motherboard. No
communication with the device is possible in backup mode.
Evaluation Board - Functional Description (see Figure 2 and Schematic)
POWER SUPPLY
The motherboard draws its power from the USB +5V ±5%
supply. If the eval board is used to provide power for other circuitry, care must be taken to keep the current draw on this supply well below 500mA which is the maximum for a USB hub-type device. There is an on-chip regulator which produces 3.3V at low output current (<10mA). The VCC for the Intersil RTC chip as well as the serial interface pullup
resistors is selectable using J3 for either 3.3V or 5V. If an external VCC supply is used it should be connected to the center pin of JP1 (shunt is removed). A ground test point is available as well.
BACKUP SUPPLY
There are two sources of backup supply available. A 100µF supercapacitor (C10) is on the board. It will provide enough backup power for the typical RTC chip to last about 1 minute at room temperature when VCC is set to 5V. There is also a CR1220 battery socket to allow removal/ replacement without soldering. This battery will last up to five years in normal backup operation. The backup supply is selectable via jumper J4 as shown in Figure 2. One row of J4 is connected to the device VBACK, and the other row to the power sources. There are four positions possible on J4, Supercap, Rechargeable, CR1220 Battery, and Ground. If no backup is used the Ground position should be used. The jumper may be removed altogether and an alternative source for VBACK can be attached to the board via the exposed header.
MICROCONTROLLER
The microcontroller used is the C8051F320. There is a dedicated I2C serial interface connected to the Intersil RTC device, EEPROM, and the temperature sensor. The power for the microcontroller comes from the USB 5V input, so the microcontroller will always be powered from 5V. Note that the P1.0 to P1.4 I/O pins for the microcontroller are available at the daughtercard connector, J2. These are for future functions and should not be loaded down or used otherwise.
J1 is a microcontroller programming connector and should not be used.
DAUGHTERCARD CONNECTOR (J2)
This connector provides power and interface signals to the daughtercard containing the Intersil RTC device as shown on the board silkscreen.
This configuration allows these signals to control the Intersil device on an external board by connecting the serial interface and ground, available at the connector. Also available are the P1.0 to P1.4 I/O signals from the microcontroller (see previous section).
USB CONNECTOR (CON1)
This connector is a standard USB type B connector which goes to the USB port of a PC using a USB type A-B cable.
LEDs
There one surface-mounted LED on the board. It is labeled POWER and it monitors the power supply and will light when the +5V power is applied from the USB cable. when the PC is communicating with the Eval board, the light will blink.
Daughtercards - Functional Description
The Daughtercards have a 10-pin female connector which matches with the Motherboard connector. There are multiple header connections on each daughtercard, the only jumper which is required to be connected with a shunt is the “Device Vcc” header, which connects Vcc power to the RTC device.
This allows the current to the RTC device to be monitored when removed. Other headers for output signals may be removed.
There is a temperature sensor on the board as well which can be used for monitoring temperature in the case of crystal frequency drift testing. The PC software can poll the temp sensor while polling the RTC time.
The devices that include event detection (ISL1209/19/21) will also have an event detect switch on the daughtercard.
There is a header with an option to turn off the internal current source and use an external pullup to Vcc or Vbat.
THE ISL12032 DAUGHTERCARD
The ISL12032 device possesses many more features than the other Intersil RTC devices so the evaluation
daughtercard is a bit more complex. The schematic is shown in Figure 3 and the layout is in Figure 4.
AC INPUT
The ISL12032 can use an external 50Hz or 60Hz AC power clock for the internal time clock. There are two ways to hook this up. One way is to use a transformer with a sine wave output, connected to JP1 (TFR). This input is conditioned by a selectable voltage divider and AC coupled to an emitter follower, which assures the peak voltages are never more than the Vdd/GND of the RTC device. The ratios for the resistor divider are as follows:
R11: 0.011 x VTRF R12: 0.118 x VTRF R13: 0.211 x VTRF
The TFR input has no polarity, connections can be reversed as long as the transformer output used is not grounded. If the TFR input is used, then a jumper MUST be placed across JP2, ACIN, so that the clock signal reaches the RTC device.
If a single ended sine wave or square wave clock source is used (such as from a waveform generator), it should be connected to the ACIN jack at JP2-2, and the signal ground should connect to a nearby ground. The amplitude should be from 1.5Vpp to 4Vpp.
EVENT FUNCTION
S1 is the Event Switch for the ISL12032, and jumper JP7 must be installed to connect the switch leads to ground.
Jumper JP8 can be used to select an external pullup resistor, with either device Vcc or Battery pullup voltage.
Remove JP8 if the internal pullup is used.
INDICATOR LEDS
JP4 and JP5 connect LEDs for the Event and IRQ-
functions, respectively. Remove these jumpers if no indicator is desired for these functions.
D3 and D4 are indicator LEDs for the AC Ready and Low Voltage detect functions, respectively. They do not have jumpers and are active at all times.
OTHER FUNCTIONS
The Fout function is at JP8-2. There is a ground connection at JP8-1 for connecting an instrument (such as a frequency counter) with a ground lead.
JP3 is the DEVICE Vcc jumper. If Device Icc current measurement is desired, remove this jumper to insert an ammeter in the circuit
.
FIGURE 2. RTC EVB Motherboard Layout SUPERCAP
BACKUP BATTERY SOCKET
VCC SELECT
DAUGHTERBOARD CONNECTOR
SHUNT FOR VBACK SELECT USB CONNECTOR
FIGURE 3. ISL12032 DAUGHTERCARD SCHEMATIC
FIGURE 4. ISL12032 DAUGHTERCARD LAYOUT
A B C D D
C
B
A Title
Size: Revision:
A
1 2 3 4 5 6 7 8 9 10 J1
SDA SCL
R1 1.2K
VCC_IN VBAT
1 2 JP4
C1 0.1uF
IRQ- Jumper DEVICE
VCC
R2 1.2K
1 2 JP5
EVDETOUT
EVDET Detect Jumper
EVIN Detect Switch 1 SDA
A0 7
4 GNDTCA
3 SCL
2
A1 6
INT 5
+VS 8
U2
LM75
D1
LTST-C230KRKT D2
LTST-C230KGKT Y1
32.76 kHz
ISL12032 TSSOP EVAL DAUGHTERCARD
1 2 JP7
R4 5M 1
2 3 JP8 1 X1
2 X2 3 VBAT 4 GND 5 AC 6 LV
7 EVINACRDYEVDETFOUTVCCSDASCLIRQ 891011121314 U1
ISL12032
1 2 JP6
EVIN VBAT VCC_DEV 1
2 JP1
R8 10k Q1 MMBT3904
VCC_IN
VCC_IN
1 2
JP2
IRQ
EVDETOUT
FOUT Jumper C2
0.01uF
FOUT
D4
LTST-C230KRKT
D3
LTST-C230KRKT
R5 1.2K
LV
R9 1.2K
VCC_IN
VCC_IN ACRDY
GND1 GND2
TP4 ACR
TP5 LV SDA
SCL
S1
GND3
1 2
JP3 C3
10 uF R16
43K
R10 68K R11 820 R12 10K R13 20K R14 75K
R15 2K
C4
1 uF
12 34 56
JP9
C5 1uF
AC IN
TFR
EVIN Pullup
Appendix A: RTC Motherboard Schematic
