DS1394U-33+T&R【PDF 3/26 页】IC RTC SPI 3WIRE W/CHRGR 10-MSOP

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Sheet目录1993

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DS1390–DS1394

Low-Voltage SPI/3-Wire RTCs with

Trickle Charger

Maxim Integrated

Pin Description

PIN

DS1390/

DS1394

DS1391

DS1392

DS1393

NAME

FUNCTION

Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator

circuitry is designed for operation with a crystal having a 6pF specified load

capacitance (CL). 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 floated if an external oscillator is connected to pin X1.

VBACKUP

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 (www.maxim-

ic.com/qa/info/w/). This pin must be grounded if not used. Diodes in series

between the battery and the VBACKUP pin may prevent proper operation.

—

SPI Chip-Select Input. This pin is used to select or deselect the part.

—

Chip Enable for 3-Wire Interface

GND

Ground

—

DIN

SPI Data Input. This pin is used to shift address and data into the part.

—

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 VCC or VBACKUP. If enabled,

INT functions when the device is powered

by either VCC or VBACKUP.

—

RST

Reset. This active-low, open-drain output indicates the status of VCC relative

to the VPF specification. As Vcc falls below VPF, the

RST pin is driven low.

When Vcc exceeds VPF, for tRST, 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,

50k

(typ) pullup resistor to VCC. No external pullup resistors should be

connected. If the crystal oscillator is disabled, the startup time of the

oscillator is added to the tRST delay.

—

DOUT

SPI Data Output. Data is output on this pin when the part is in read mode.

CMOS push-pull driver.

—

I/O

Input/Output for 3-Wire Interface. CMOS push-pull driver.

SCLK

Serial Clock Input. This pin is used to control the timing of data into and out

of the part.

—

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

VCC or VBACKUP. If enabled, SQW/

INT functions when the device is powered

by either VCC or VBACKUP. If not used, this pin can be left open.

—

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 VCC or

VBACKUP. If enabled, SQW functions when the device is powered by either

VCC or VBACKUP. If not used, this pin can be left open.

VCC

DC Power Pin for Primary Power Supply

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