Datasheet

PIN
NAME
FUNCTION
DS1390/
DS1394
DS1391 DS1392 DS1393
1 1 1 1
X1
Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator
circuitry is designed for operation with a crystal having a 6pF specied load
capacitance (C
L
). Pin X1 is the input to the oscillator and can optionally be
connected to an external 32.768kHz oscillator. The output of the internal
oscillator, pin X2, is oated if an external oscillator is connected to pin X1.
2 2 2 2 X2
3 3 3 3 V
BACKUP
DC Backup Power Input for Primary Cell. This pin is a rechargeable battery/
super cap or a secondary supply. UL recognized to ensure against reverse
charging current when used with a lithium battery (http://www.maximintegrated.
com/qa/info/w/). This pin must be grounded if not used. Diodes in series
between the battery and the V
BACKUP
pin may prevent proper operation.
4 4 — — CS SPI Chip-Select Input. This pin is used to select or deselect the part.
— — 4 4 CE Chip Enable for 3-Wire Interface
5 5 5 5 GND Ground
6 6 — — DIN SPI Data Input. This pin is used to shift address and data into the part.
— — 6 — INT
Interrupt Output. This pin is used to output the interrupt signal, if enabled by
the control register. The maximum voltage on this pin is 5.5V, independent of
V
CC
or V
BACKUP
. If enabled, INT functions when the device is powered
by either V
CC
or V
BACKUP
.
— 9 — 6 RST
Reset. This active-low, open-drain output indicates the status of V
CC
relative to
the V
PF
specication. As V
CC
falls below V
PF
, the RST pin is driven low. When
V
CC
exceeds V
PF
, for t
RST
, the RST pin is driven high impedance.
This pin is combined with a debounced pushbutton input function. This pin can
be activated by a pushbutton reset request. This pin has an internal, 50kΩ (typ)
pullup resistor to V
CC
. No external pullup resistors should be connected. If the
crystal oscillator is disabled, the startup time of the oscillator is added to the
t
RST
delay.
7 7 — — DOUT
SPI Data Output. Data is output on this pin when the part is in read mode.
CMOS push-pull driver.
— — 7 7 I/O Input/Output for 3-Wire Interface. CMOS push-pull driver.
8 8 8 8 SCLK
Serial Clock Input. This pin is used to control the timing of data into and out
of the part.
9 — — 9 SQW/INT
Square-Wave/Interrupt Output. This pin is used to output the programmable
square wave or interrupt signal. When enabled by setting the ESQW bit
to logic 1, the SQW/INT pin outputs one of four frequencies: 32.768kHz,
8.192kHz, 4.096kHz, or 1Hz. This pin is open drain and requires an external
pullup resistor. The maximum voltage on this pin is 5.5V, independent of V
CC
or V
BACKUP
. If enabled, SQW/INT functions when the device is powered by
either V
CC
or V
BACKUP
. If not used, this pin can be left open.
— — 9 — SQW
Square-Wave Output. This pin is open drain and requires an external pullup
resistor. The maximum voltage on this pin is 5.5V, independent of V
CC
or
V
BACKUP
. If enabled, SQW functions when the device is powered by either
V
CC
or V
BACKUP
. If not used, this pin can be left open.
10 10 10 10 V
CC
DC Power Pin for Primary Power Supply
www.maximintegrated.com
Maxim Integrated │ 12
DS1390–DS1394 Low-Voltage SPI/3-Wire RTCs
with Trickle Charger
Pin Description