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DS1391 Schematic ( PDF Datasheet ) - Maxim Integrated Products

Teilenummer DS1391
Beschreibung (DS1390 - DS1393) Low-Voltage SPI/3-Wire RTCs
Hersteller Maxim Integrated Products
Logo Maxim Integrated Products Logo 




Gesamt 24 Seiten
DS1391 Datasheet, Funktion
www.DataSheet4U.com
Rev 0; 7/04
Low-Voltage SPI/3-Wire RTCs with
Trickle Charger
General Description
The low-voltage serial-peripheral interface (SPI™)
DS1390/DS1391 and the low-voltage 3-wire DS1392/
DS1393 real-time clocks (RTCs) are clocks/calendars
that provide hundredths of a second, seconds, min-
utes, hours, day, date, month, and year information.
The date at the end of the month is automatically
adjusted for months with fewer than 31 days, including
corrections for leap year. The clock operates in either
the 24-hour or 12-hour format with an AM/PM indicator.
One programmable time-of-day alarm is provided. A
temperature-compensated voltage reference monitors
the status of VCC and automatically switches to the
backup supply if a power failure is detected. On the
DS1390, a single open-drain output provides a CPU
interrupt or a square wave at one of four selectable fre-
quencies. The DS1391 replaces the SQW/INT pin with a
RST output/debounced input.
The DS1390 and DS1391 are programmed serially
through an SPI-compatible, bidirectional bus. The
DS1392 and DS1393 communicate over a 3-wire serial
bus, and the extra pin is used for either a separate
interrupt pin or a RST output/debounced input.
All four devices are available in a 10-pin µSOP package,
and are rated over the industrial temperature range.
Features
Real-Time Clock Counts Hundredths of Seconds,
Seconds, Minutes, Hours, Day, Date, Month, and
Year with Leap-Year Compensation Valid Up to
2100
Output Pin Configurable as Interrupt or Square
Wave with Programmable Frequency of
32.768kHz, 8.192kHz, 4.096kHz, or 1Hz
(DS1390/DS1393 Only)
One Time-of-Day Alarm
Power-Fail Detect and Switch Circuitry
Reset Output/Debounced Input (DS1391/DS1393)
Separate SQW and INT Output (DS1392)
Trickle-Charge Capability
SPI Supports Modes 1 and 3 (DS1390/DS1391)
3-Wire Interface (DS1392/DS1393)
4MHz at 3.0V and 3.3V
1MHz at 1.8V
Three Operating Voltages: 1.8V ±5%, 3.0V ±10%,
and 2.97 to 5.5V
Industrial Temperature Range: -40°C to +85°C
Underwriters Laboratory (UL) Recognized
Applications
Hand-Held Devices
GPS/Telematics Devices
Embedded Time Stamping
Medical Devices
Typical Operating Circuits and Pin Configurations appear at
end of the data sheet.
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
TOP MARK
DS1390U-18 -40°C to +85°C 10 µSOP DS1390 rr-18
DS1390U-3
-40°C to +85°C 10 µSOP DS1390 rr-3
DS1390U-33 -40°C to +85°C 10 µSOP DS1390 rr-33
DS1391U-18 -40°C to +85°C 10 µSOP DS1391 rr-18
DS1391U-3
-40°C to +85°C 10 µSOP DS1391 rr-3
DS1391U-33 -40°C to +85°C 10 µSOP DS1391 rr-33
DS1392U-18 -40°C to +85°C 10 µSOP DS1393 rr-18
DS1392U-3
-40°C to +85°C 10 µSOP DS1392 rr-3
DS1392U-33 -40°C to +85°C 10 µSOP DS1392 rr-33
DS1393U-18 -40°C to +85°C 10 µSOP DS1393 rr-18
DS1393U-3
-40°C to +85°C 10 µSOP DS1393 rr-3
DS1393U-33 -40°C to +85°C 10 µSOP DS1393 rr-33
Where “rr” is a revision code on the second line of the top mark.
SPI is a trademark of Motorola, Inc.
______________________________________________ Maxim Integrated Products 1
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.






DS1391 Datasheet, Funktion
www.DataSheet4U.com
Low-Voltage SPI/3-Wire RTCs with
Trickle Charger
CE
tCC
SCLK
tDC
I/O
tCDH
A0
tR tF
tCL tCH
A1
WRITE ADDRESS BYTE
Figure 3. Timing Diagram—3-Wire Read Transfer
R/W
tCDD
D0
READ DATA BYTE
tCDZ
D7
CE
SCLK
tDC
I/O
tCC
tCDH
A0
tR
tCL
tCH
A1
tF
R/W
WRITE ADDRESS BYTE
Figure 4. Timing Diagram—3-Wire Write Transfer
tCWH
tCCH
D0 D7
WRITE DATA BYTE
6 _____________________________________________________________________

6 Page









DS1391 pdf, datenblatt
www.DataSheet4U.com
Low-Voltage SPI/3-Wire RTCs with
Trickle Charger
However, when VCC falls below VPF, the internal clock
registers are blocked from any access. If VPF is less
than VBACKUP, the device power is switched from VCC
to VBACKUP when VCC drops below VPF. If VPF is
greater than VBACKUP, the device power is switched
from VCC to VBACKUP when VCC drops below
VBACKUP. The registers are maintained from the
VBACKUP source until VCC is returned to nominal levels.
See the Functional Diagram for the main elements of
these serial RTCs.
Table 1. Crystal Specifications*
PARAMETER SYMBOL MIN TYP MAX UNITS
Nominal Frequency
Series Resistance
fO
ESR
32.768
55
kHz
k
Load Capacitance
CL
6 pF
*The crystal, traces, and crystal input pins should be isolated
from RF generating signals. Refer to Application Note 58:
Crystal Considerations for Dallas Real-Time Clocks for addi-
tional specifications.
Oscillator Circuit
All four devices use an external 32.768kHz crystal. The
oscillator circuit does not require any external resistors
or capacitors to operate. Table 1 specifies several crys-
tal parameters for the external crystal, and Figure 7
shows a functional schematic of the oscillator circuit. If
a crystal is used with the specified characteristics, the
startup time is usually less than one second.
Clock Accuracy
The accuracy of the clock is dependent upon the accu-
racy of the crystal and the accuracy of the match
between the capacitive load of the oscillator circuit and
the capacitive load for which the crystal was trimmed.
Additional error is added by crystal frequency drift
caused by temperature shifts. External circuit noise
coupled into the oscillator circuit can result in the clock
running fast. Figure 8 shows a typical PC board layout
for isolation of the crystal and oscillator from noise.
Refer to Application Note 58: Crystal Considerations
with Dallas Real-Time Clocks for detailed information.
COUNTDOWN
CHAIN
CL1 CL2 RTC REGISTERS
DS139x
X1 X2
CRYSTAL
Figure 7. Oscillator Circuit Showing Internal Bias Network
LOCAL GROUND PLANE (LAYER 2)
CRYSTAL
NOTE: AVOID ROUTING SIGNAL LINES
IN THE CROSSHATCHED AREA
(UPPER LEFT QUADRANT) OF
THE PACKAGE UNLESS THERE IS
A GROUND PLANE BETWEEN THE
SIGNAL LINE AND THE DEVICE PACKAGE.
Figure 8. Layout Example
X1
X2
GND
12 ____________________________________________________________________

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