DS1390_09 Datasheet, PDF (11/26 Pages) Maxim Integrated Products – Low-Voltage SPI/3-Wire RTCs with Trickle Charger

Low-Voltage SPI/3-Wire RTCs with
Trickle Charger
Pin Description
PIN
DS1390/
DS1394
DS1391
DS1392
DS1393
NAME
FUNCTION
Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator
1
1
1
1
X1
circuitry is designed for operation with a crystal having a 6pF specified load
capacitance (C_L). Pin X1 is the input to the oscillator and can optionally be
2
2
2
2
X2
connected to an external 32.768kHz oscillator. The output of the internal
oscillator, pin X2, is floated if an external oscillator is connected to pin X1.
DC Backup Power Input for Primary Cell. This pin is a rechargeable
battery/super cap or a secondary supply. UL recognized to ensure against
3
3
3
3
V_BACKUP reverse charging current when used with a lithium battery (www.maxim-
ic.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.
Interrupt Output. This pin is used to output the interrupt signal, if enabled by
—
—
6
—
INT
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.
Reset. This active-low, open-drain output indicates the status of V_CC relative
to the V_PF specification. As Vcc falls below V_PF, the RST pin is driven low.
When Vcc exceeds V_PF, for t_RST, the RST pin is driven high impedance.
—
9
—
6
RST ^{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,
50k
(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.
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,
9
—
—
9
SQW/INT 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.
Square-Wave Output. This pin is open drain and requires an external pullup
—
—
9
—
SQW ^{resistor. The maximum voltage on this pin is 5.5V, independent of VCC 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
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