DS1390-DS1393 MAXIM [Maxim Integrated Products], DS1390-DS1393 Datasheet - Page 11

• Manufacturer Part Number: DS1390-DS1393
• Description: Low-Voltage SPI/3-Wire RTCs with Trickle Charger
• Manufacturer: MAXIM [Maxim Integrated Products]

The DS1390/DS1391/DS1392/DS1393 RTCs are low-
power clocks/calendars with alarms. Address and data
are transferred serially through a 4-wire SPI interface
for the DS1390 and DS1391 and through a 3-wire inter-
face for the DS1392 and DS1393. The clocks/calendars
provide hundredths of seconds, seconds, minutes,
hours, day, date, month, and year information. The
alarm functions are performed off all timekeeping regis-
ters, allowing the user to set high resolution alarms. The
date at the end of the month is automatically adjusted
for months with fewer than 31 days, including correc-
tions for leap year. The clocks operate in either the 24-
hour or 12-hour format with an AM/PM indicator. All four
devices have a built-in temperature-compensated volt-
age reference that detects power failures and automati-
(DS1390/91) DOUT
(DS1392/93) (CE)
(DS1390/91) DIN
(DS1390/91) CS
(DS1392/93) I/O
V
BACKUP
SCLK
GND
V
X1
X2
CC
Detailed Description
V
TRICKLE CHARGER
CC
POWER SWITCH,
WRITE PROTECT,
OSCILLATOR
INTERFACE
LEVEL DETECT,
CRYSTAL
32,768Hz
BUS
Low-Voltage SPI/3-Wire RTCs with
____________________________________________________________________
WITH HUNDREDTHS
ALARM REGISTERS
TRICKLE REGISTER
REAL-TIME CLOCK
CONTROL/STATUS
HUNDREDTHS-OF-
OF SECONDS
REGISTERS
GENERATOR
SECONDS
cally switches to the battery supply. Additionally, the
devices can provide trickle charging of the backup
voltage source, with selectable charging resistance
and diode voltage drops.
The DS1390/DS1391 operate as a slave device on the
SPI serial bus. The DS1392/DS1393 operate using a
3-wire synchronous serial bus. Access is obtained by
selecting the part by the CS pin (CE on DS1392/
DS1393) and clocking data into/out of the part using
the SCLK and DIN/DOUT pins (I/O on DS1392/
DS1393). Multiple-byte transfers are supported within
one CS low period (see the SPI Serial-Data Bus sec-
tion). The devices are fully accessible and data can be
written and read when V
DS1390/DS1391/
DS1392/DS1393
SELECTOR, INT, MUX,
SQUARE-WAVE RATE
Trickle Charger
RST OUTPUT
Functional Diagram
CC
is greater than V
Operation
SQW/INT (DS1390/93)
RST (DS1391/93)
SQW (DS1392)
PF
11
.