DS1302 Trickle-Charge Timekeeping Chip

4 of 16

PIN DESCRIPTION

PIN

8

16

NAME

FUNCTION

1

1

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

DS1302.

2

3

X1

3

5

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

8

GND

Ground

5

9

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

12

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

14

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

16

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.

—

2, 4, 6,

7, 10,

11, 13,

15

N.C.

No Connection