DS1302 Trickle-Charge Timekeeping Chip

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PIN DESCRIPTION

PIN

NAME

FUNCTION

1

backup source to maintain the time and date in the absence of primary power. The

DS1302.

2

X1

3

X2

Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator is

designed for operation with a crystal having a specified load capacitance of 6pF.

For more information on crystal selection and crystal layout considerations, refer to

Application Note 58: Crystal Considerations for Dallas Real-Time Clocks

. The

DS1302 can also be driven by an external 32.768kHz oscillator. In this

configuration, the X1 pin is connected to the external oscillator signal and the X2 pin

is floated.

4

GND

Ground

5

CE

Input. CE signal must be asserted high during a read or a write. This pin has an

internal 40k

Ω (typ) pulldown resistor to ground. Note: Previous data sheet revisions

referred to CE as

RST. The functionality of the pin has not changed.

6

I/O

Input/Push-Pull Output. The I/O pin is the bidirectional data pin for the 3-wire

interface. This pin has an internal 40k

Ω (typ) pulldown resistor to ground.

7

SCLK

Input. SCLK is used to synchronize data movement on the serial interface. This pin

has an internal 40k

Ω (typ) pulldown resistor to ground.

8

Low-Power Operation in Single Supply and Battery-Operated Systems and Low-

Power Battery Backup. In systems using the trickle charger, the rechargeable

energy source is connected to this pin. UL recognized to ensure against reverse

charging current when used with a lithium battery. Go to www.maxim-

ic.com/TechSupport/QA/ntrl.htm

.